Whats the basic rule of thumb for jetting and altitude with a holley style carb? I have been told you decrease 1 jet size for every 2000 feet above sea level and I have been told you decrease 1 size for every 1000 feet above sea level.
I live 4000 feet above sea level and I run a quick fuel super street series 680cfm vaccum secondary carburetor on a 300 hp crate 360 magnum. The other day I noticed the engine was a little shakey and felt different so I decided to check my pugs, I had 3 fouled plugs. And I think this happened because I forgot to install the primary vent on thhe primary metering block and it flooded the crap out of my engine. This carburetor came with 68 main jets and 78 secondary jets and .070 idle air bleeds and .031 idle feed restrictors and .049 power valve channel restrictors and a 6.5hg power valve and .028 high speed bleeds.
Since getting this carburetor last summer I had to go down to .025 idle feed restrictors because the .031's were fouling plugs at idle and I am running .072 idle air bleeds and I went down to 64 main jets and 74 secondary jets and I went down to .045 power valve channel restrictors and I have left the high speed bleeds alone at .028 and I switched to a 9.5hg power valve.
I was wondering if it is possible that the 64 main jets are too big? Like I said I'm pretty sure the reason the plugs fouled was due to the vent that I didn't put back in on the primary metering block. I have my floats set to half way up the sight glass. And all 4 of my idle mixture screws are out about 1.25 turns on all 4 screws.
I have some holley .063 main jets I installed them and ran them for a couple of days and I didn't hear any pinging or feel anything significantly different then how it ran with the .064 main jets. So today I put the .064 main jets back in it and am going to see if I can tell a difference between them and the .063's.

I'd not stray from the basic "one change at a time" rule. I'd get the vent taken care of & check if the float level should be at the bottom of the hole or where you have it halfway up. Wallace racing has excellent pics of plugs for jetting/heat range or an innovate LM1 is the best/pro way to get it spot on

yes I know a lm1 would take all the guess work out of this, but unforutently I cant afford one of those at the moment. Tonight I decided to richen up my idle air bleeds from .072's to .070's and I started the engine and the choke was on letting it warm up and the choke opened but my fast idle was still on and it is popping thru the exhaust sounding a little lean and when I looked under the hood I noticed my passenger side hedders were glowing red. What the hell is up with that? I'm running 64 main jets at 4000 feet above sea level. Which is what quick fuel suggested running it. I read this was most likely un-burnt fuel burning in the exhaust and that when I loaded the engine it would go away. My timing is 15 degrees initial and 33 degrees total. I have never noticed this before because I haven't really messed with it after dark. What do I do about this?

Well I just tried swapping him some .065 idle air bleeds and same thing, the hedders start to glow red right at about 2500 rpm when your holding the throttle open and steady. When I noticed them starting to glow red I gave the engine 3 or 4 shots of fuel with the accelerator pump and I noticed that made it go away. So are my main jets too lean at 64? I have some 65's I could try. This is strange to me because it runs great going down the road, no surging, no popping, no hesitations anywhere. I figured since they stopped glowing when I gave it a few shots of fuel with the accelerator pump then that means it's too lean. Correct?

Maybe holley saying 1 jet size for every 2000 feet above sea level is more accurate

I've heard guys on here say that RPM with no load will cause the carb to go lean, thus red headers.

That said, before I knew anything about AFRs, rich/lean, etc. When I took my car out to Colorado, I followed the chart that Edelbrock provided with the carb, on what jets/rods to use at various elevations. The car ran and drove fine the 2 years I had it out there. ALthough, it didn't have any power, but what NA motor does at 7,000 feet ACTUAL elevation? I'd bet the DA on most days was up near 10-12k

One jet size per 2000 Feet has been my experience. I live at 4500 feet and usually make an annual trip to see family that live at 200 Feet. To tune the car back to "normal" would take 2 jet sizes and taking about 2 degrees out of the timing.

Yes too lean will make em glow red as will way too rich & it's burning in the ex but for it to go away when you pumped it tells you which one you are dealing with. I'm assuming there is no vac leak that is skewing this and the float levels are correct. I'd k.i.s.s. richen those jets ASAP before something fries.

It appears from what you have written that you are lean from idle to 2500rpms which would point to the idle/transfer circuit, not the main jetting. The idle and transfer consist of the Idle Feed Resisters, Idle Air Bleeds, and the metering screws. You noted that your metering screws are 1-1/4 turns out which sounds like a lot for a QF carb. If you richened up your IFR's, you might be able to get the metering screws back down under 1 turn (Z at QF suggests under one turn out each.)

My guess is that your .025 IFR's are too lean and you are making up for that by turning your metering screws outward to 1-1/4 turns. Once you are off idle, the metering screw setting still affect the A/F during the transition into the main circtuit. But, above idle, the IFR's and the IAB's are also contributing to your A/F ratio. Since you richened it up by adding 3-4 pump shots, that is telling you that you are lean and could be the real reason for the red headers. I would suggest going back up to the .031 IFR's to richen up your transition circuit.


(REF NOTES ONLY: On my Super Street QF carb, my mains start in around 2500-2700rpms. In four years, I have never had my metering screws in or out more or less than 1/2 to 7/8 turn outward each. I currently run .033IFR's and .050 front and .060 rear IAB's and I get 14.0-14.2 at 45mph which is 2400rpms but I am at a lower elevation than you. I looked back at my tuning notes and I found that when I first started tuning with an A/F meter, I was running with .028 IFR's and my 1700rpm cruise was WAY LEAN at 17.0 and my 2500rpm cruise was still lean at 15.6. [E10 fuel]. QF also suggests floats set at 1/2 up the glass. My SS also came with 68 main jets and I am now running 67's. I have tried 58-67 main jets with many other changes while testing A/F ratio's. The 67's give me mid 13 A/F readings at cruising speeds at 55-65mph [2700-3300rpms] which is my current goal) and they give me the most throttle response when my PV is open [along with .078 PVCR's])

When I was running .031 idle feed restrictors my plugs were fouling at idle it was so rich. I have 3 .028 idle feed restrictors but I broke the 4th one so I need a new .028. What size of idle air bleeds should I run when I swap to the .028 idle feed restrictors? .070's? or .072's? This has me confused. I even dropped the idle air bleeds down to .065 from .070 and it didn't change the lean condition with the hedders.

And another thing that is confusing me is that it doesn't act like it's lean when your driving it, it acts like it's perfect. But when it's sitting in park idling with the fast idle on it pops out the exhaust and the hedders start to glow red. Why doesnt act lean while driving it?

I'm assuming your timing is in the ballpark at the particular fast idle RPM that makes em glow red. This might be too simple but I'd think it could be way too lean at (fast) idle (the idle circuit) but the transition/mains are in the normal range & it richens up enough to straighten out.

Yes timing is set at 15 degrees initial and 33 degrees total. I have some .028 idle feed restrictors, but I only have 3. So I will put some .028 idle feed restrictors in the primary metering block and see what that does. If it helps then I will order another .028 idle feed restrictor and put them in the secondary metering block as well.

""When I was running .031 idle feed restrictors my plugs were fouling at idle it was so rich.""

Then you compensate with the metering screws. If I remember correctly, you have an auto. The next time you have the engine running and if you can take it for a short drive to get it up to temp, then put the car in D (with emergency brake or someone behind the wheel) and tune the metering screws evenly until you get the best vacuum reading at the idle rpm of your choosing.
The goal is you have the highest vacuum reading at your chosen rpm and the metering screws are all outward even. This vacuum number becomes your goal after any future idle adjustments. Always meet this number or get higher at the same rpms.
You will need to readjust the metering screws every time you change the IFR's or the IAB's.
I would still suggest that you retry the 031's and then readjust your metering screws for the highest vacuum reading. Then if your metering screws are still outward more than 1 full turn, then drop down (richen up IAB's).005 sizes (or what ever size you have) and then readjust your metering screws once again. You are super lean at high idle (apx 1200-1500rpms or so?) and this is the IFR's/IAB's or the metering screws. Since your metering screws are out 1-1/4 turns, I think your IFR's are tooooooo small. You need to fix the glowing headers first and then lean out your idle in D. Fix the leaking baffle that you wrote about too.
If you don't want to go larger on your existing .025 IFR's, then put some small wire down inside of your IAB's to test. This will make the IAB's smaller/richer but I am not sure it will be enough.

What seems strange to me is, there was no symptom of a lean condition while driving it. Only when it was sitting in park. Why is that? With the hedders glowing red you'd think there would be a lean stumble or hesitation at lower speeds but there isn't, in fact it runs great when your driving it around. The only reason I noticed this is because I had the fast idle going with the hood popped when it was dark outside.

""there was no symptom of a lean condition while driving it. Only when it was sitting in park. Why is that?""

When you are sitting in P at high idle, you are idling on the transition circuit. When you are tooling around town, you have help from the front pump circuit to help on acceleration until your mains start in. The pump circuit is a designed-in "bandaid" to help cover up any lean spikes during the transition into the mains. It sounds like your current pump setup (squirters/pump cam) is doing its job along with the .028/64 main setup.

Since you are using 64 jets and .028" MAB's (fairly rich which starts the main circuit sooner than a .033" for reference), this may be allowing the main circuit (jets and MAB's) to start fairly early and the main circuit may be tuned fine. This might be why you do not have any known issues while cruising.
Please concentrate on richening the IFR's and the IAB's.

I really need a wideband so I can take all the guess work out. Starting today I'm setting some money aside for one.

They are not only a tuning tool but a teaching tool as well! You can have a gauge/O2 sensor kit for apx $190.

The only reason I am scared to run the .031 idle feed restrictors is because last time I had them in the carb 4 of my plugs fouled at idle and I was setting my idle mixture screws to the best vaccum reading in drive with the brake applied. That didn't matter plugs stil fouled.
I have noticed my engine fouls plugs super easy, and I did take care of the vent, I didn't break the vent I just simpily forgot to put it back in.
You also have to remember I live 4000 feet above sea level, so since .031's work fine on your 340 right now, if you came up here you might notice they are too big. I don't want to foul any more plugs, I am tired of removing wires and plugs all the time. I have 8 fresh plugs in there right now and I am about 80 percent sure if I changed back to the .031 idle feed restrictors some of my plugs would be fouled regardless of where my idle mixture screws were. And I just double checked my idle mixture screws and they are all out about 1 turn.

Plus the biggest idle air bleeds I have right now are .072's. Running .031 idle feed restrictors the .072 idle air bleeds probly wouldn't be lean enough to keep my plugs from fouling.

ok I put .028 idle feed restrictors in the primary metering block. And I started it and it still had some lean popping out the exhaust with the fast idle on but it wasn't as bad as it was when it had the .025 ifr's in it, but it's definitely still lean. I found all 4 of the .031 idle feed restrictors that came in the carb. I am hesitant to run them because I am worried it will foul my plugs. But something I forgot to add, Back when my plugs were fouling with the .031 idle feed restrictors in it I was running a 1 inch 4 hole spacer and now I am running a 2 inch 4 hole spacer. Could that extra inch of spacer contribute to the engine being leaner in the transisition circuit?

I think you went backwards on some adjustments from the original post? I would use the original restriction and bleeds, they sounded OK. Check vacuum in gear and use a power valve that is 1/2 or lower than that, so if you have 10" vacuum, use a 4.5 power valve. Once the carb is set at your idle speed, pull the carb and check that the throttle blades are not so far open they are exposing the transfer slot. A small amount of exposed transfer slot (so it looks like a square) is OK. If the transfer slot is exposed, you may be able the crack the rear throttle blades a small amount. I don't know it the carb has an adjustable idle air bleed? I usually have to drill the throttle blades to allow a bit of idle air through with the throttle blades don't expose the transfer slot. I would then just work on adjusting your jetting and accelerator pump.

I read through the rest of the posts. As I mentioned above, make sure the throttle blades are not too far open at idle, then the idle screws can be adjusted for the correct mixture. The spark plugs might also be too cool a heat range for your combination causing them to foul easier than they should.

You should not be fouling plugs that quickly.

- 451 has a good point: what plugs are you using?
- 15 degrees initial timing may not be enough
- If the .028 front IFR's helped out on the lean idle, then that is your hint to keep going that direction and maybe one of the above items is the actual reason as to why you are fouling plugs.

My initial timing is set at 15 degrees, but I have my vaccum advance hooked up to manifold vaccum which adds another 15 degrees of timing at idle. So at idle I have 30 degrees from my 15 degrees of intial timing plus the 15 degrees of timing the vaccum advance Is adding.
I am running NGK BKR5E plugs and I have all 8 of my plugs indexed and they are gapped at .045. I know my ignition is up to snuff, it's a brand new crane cams hi-6 cd ignition with a crane cams lx91 ignition coil and my plug wires are brand new taylor thundervolt 8.2mm wires.
Distributer is a mopar unit built by don at fbo systems.
I agree I shouldn't be fouling plugs that easy ether, but this engine has always seemed to foul plugs easily for some reason. This engine was purchased brand new by my father in 2002 and I acquired it in 2010, it has around 20 thousand miles on it. I have done a compression test with the engine warm and carburetor all the way open and every cylinder is at 150psi. Which I am told is good for 4000 feet above sea level.
Is it possible maybe the 64 main jet and the .049 power valve channel restrictors were the culprit for fouling the plugs? I have some .063 main jets and some .045 power valve channel restrictors. I am going to put the .031 idle feed restrictors back in it tonight and see what happens, I will run the biggest idle air bleeds I have which are .072's. I'm going to order some .029 and some .030 idle feed restrictors tonight and a few different idle air bleeds. Maybe some .074's and some .076's.
There are no vaccum leaks on the engine, An my power valve is fine I checked it last night it is a quick fuel 9.5hg power valve, float level is half way up the sight glass with 6 lbs of fuel pressure at idle.
I don't know what was fouling my plugs back when I first installed this carburetor and was running the .031 idle feed restrictors. But I think adding this 2 inch spacer has leaned things down considerably, so maybe the .031 idle feed restrictors will be ok with this 2 inch spacer. I will let you guys know what happens when I install the .031 idle feed restrictors tonight. Thanks for everyones help with this.

Post a picture of one of the fouled plugs A NGK 5 plug should not foul easily at part throttle,even at the hieght you are above sea level

The spark plug heat range sounds good too. That kind of leads me to think your throttle blades may be too far into the transition circuit?
I have found that at higher altitude, most carbs want a larger idle restrictor because there is less air pressure above the fuel, and the engine will also have less vacuum. I have never had an engine at this altitude (6,000 ft) that needed anything higher than a 6.5 power valve, usually I am using 3.5 to 5.5 power valves.
If you have a rear power valve, check it too to make sure fuel is not flowing past a blown power valve.

well I am confused but I think I might know what was going on before with the plugs fouling. I just realized that my idle mixture screws were 2 turns out on all 4 with the .025 idle feed restrictors. I was counting one full revolution of the screwdriver as 1 turn. I installed the .031 ifr's in it tonight and I put my largest .072 set of idle air bleeds in it and I fired it up with the choke on and while it was on the fast idle it wasn't popping like it was with the .025 and .028 ifr's, I thought I heard a few faint pops here and there but nothing really loud, you have to listen for them.
Anyways got it up to operating temp and I put the transmission in drive and blocked my rear tires. Then I set the idle mixture screws to the best vaccum reading. That ended up being 1 turn out on all 4 mixture screws and I noticed that the mixture screws are a lot more responsive now. 1/4 of a turn in or out makes the idle vaccum go down and you can hear a change in the idle. I also lowered my float a little bit because I figured going to the larger .031 ifr's might be too much, I lowered them down to the bottom of the sight glass instead of being half way up the sight glass.
Now my guess for the plugs fouling is because I forgot to put the vent back in on the primary metering block and I know it flooded the crap out of my engine. And my guess to why I fouled some plugs when I first installed the carburetor is because I think I left it running too long with the idle mixture screws being way too rich because iremember seeing black smoke coming from exhaust.
It seems to be doing a lot better right now with the .031 ifr's and the .072 iab's. I will run it for a few days and pull the plugs again and check them out.

I was thinking the float level is supposed to be at the bottom of the sight hole? To where it would just spill if you rocked the eng slightly. From your last post it sounds like you ARE making good progress

Nice job!!!
If you need to lean it out any more in the future, then just swap out the .072 IAB's for some .075/.078's or something in that area then reset your in D idle vacuum again and test again. Do what you can to keep the four metering screws between 1/2 - 1 turn out. These QF carbs don't like much more than 1 turn.

You now need to go out and drive it for a while to clean up those plugs. Have fun!

I am very glad to have gotten this some what figured out. I am going to invest in a wideband and I will get one in the near future. I just ordered 4 .030 quick fuel ifr's and 4 .075 quick fuel Iab's. And it looks like I wont even be needing them. I have some .032 and .033 quick fuel ifr's already. Should I try the .032 ifr's and see if that takes the lean popping sound completely away?
It only does it for a minute or so when you first fire it up and the fast idle is on, it has some faint pops in the exhaust here and there. Could that be telling me to go even bigger on the ifr's? Or smaller on the idle air bleeds?

Since you found improvement with the .031's, then retest with the .033's. You will need to reset your in D vacuum again.
Then test with the different IAB's that you have.

Since the IFR's and the IAB's work together, look at the IFR's as your "internal adjustment" and the IAB's as your "external adjustment". If you have three sets of IAB's, then test with all three to see if it makes a difference. If the three sets that you have do not give you the results that you want, then open the carb and change the IFR's then retest with the three sets of IAB's again if needed.
You usually want to change the IFR's in small increments (.002-.003" at a time). The IAB's can be changed in larger increments (.005" or so).

I would test your smallest IAB's along with the .033 IFR's. If your smallest IAB's are not small enough, then take a small wire and insert it down into each of the primary IAB's and bent the top of the wire so that it goes down into the carb body so it will not fall out. This will reduce the IAB hole and allow you to test a richer setup before buying more IAB's.

I spoke too soon it looks like. Since changing to the .031 idle feed restrictors and .072 idle air bleeds I noticed I have some black smoke coming out the exhaust when I have it idling in park and I give it some gas. I'm guessing this is because something is too rich and I think its the ifr's and iab's. I will pull my plugs and find out if any of them are fouled.

I would definitely get the LM1 & get the systems spot on in order. The carb tech given here is extremely good

"I spoke too soon it looks like. Since changing to the .031 idle feed restrictors and .072 idle air bleeds I noticed I have some black smoke coming out the exhaust when I have it idling in park and I give it some gas."

Did you reset your metering screws?
(Note: .031 IFR / .072 IAB is not what I would call a rich setup, it is more lean if anything.)


What size pump cam/squirter do you have?

Note: It sounds like you may have a component adding too much fuel at/or off idle. If the above seem normal, check to see if you have any rotation in your power valve assembly. Hold each end of your PV with each hand. If you can spin either end of your PV, then IT WILL LEAK even if the engine is not even running [if the fuel level in the bowl is at or above the PV level]. QF gave me this advice a few months back and I found my existing QF pv and one of my spare Holley pv's could twist. Don't use a lot of force, but just see if the PV assembly is intact.

Well I'm pretty sure I have fouled a plug or two because the exhaust at idle is super rich smelling and the idle doesn't sound right out of the exhaust.
My power valve is brand new so I don't see why it would have an issue or be leaking, but I will check it out when I tear back into carburetor. The .030 ifr's and .075 iab's I ordered wont be here until Friday. I double checked my timing tonight and it's at 16 degrees initial 34 total, vaccum advance on manifold vaccum adding another 14 degrees at idle.
My ignition should be more then enough to fire my plugs it's a crane cams hi-6 cd ignition with a crane cams lx91 ignition coil. My wires are brand new taylor thundervolt 8.2mm. This is so frustrating it seems like no matter what I do I'm fouling plugs some how some way, even with the .025 ifr's I fouled some plugs. I don't know what to do to eliminate this issue, but I think it is fuel related because my plugs are black and sooty looking like a chimney when I do foul them.
I have some different plugs I am going to try if I have fouled some plugs, they are NGK V-power zfr5f11's and they are a little bit longer then the ngk v-power bkr5e's that I am running now, the zfr5f11's look like they would run a little hotter since they go down into the combustion chamber a little further.
I am going to install the .030 ifr's and .075 iab's when they get here and these different plugs.
I'm running an orange accelerator pump cam in the number 1 position and I am running .035 accelerator pump squiters with the hi-flow accelerator pump nozzle screw. Can an accelerator pump foul plugs? I have never heard of that before. But if it's possible I can try some smaller squiters I have a .031 and a .033 squirter.

And yes I re-set my idle mixture screws. I put it in drive and blocked my tires and I set it to the highest vaccum reading, which ended up being about .075 to 1 turn out on all 4 mixture screws.

"" I'm running an orange accelerator pump cam/.035 squirter"
- The ORANGE cam is the second largest 30cc pump cam. It is very aggressive off idle and "could" cause the black smoke at the blip of the throttle. Try using a less aggressive pump cam (white/black).

Check your power valve as noted. My NEW 10.5 QF power valve was bad and QF is who told me to check it!!
Double check that you tightened down the IFR's. If they are not tight, the fuel would leak past them. I know that they are small but just make sure that they are snugged up.

I am still guessing that "something" is leaking on you that is causing the fouled plugs since you have seen this since running the .025 IFR's. You have found that .025 & .028 IFR's are too lean, so maybe the .030's might help out a bit.

Check the power valve gaskets to make sure they are seal up against the metering plate correctly, it is very easy to get the gasket cocked, out of round, and make it leak I have done that I now install the power valve with the gasket holding the metering block with the jets pointed up so I can watch the gasket seat squarely agianst the sealing surface on the metering block Once you have it seated properly tighten it down well, not lightly

What Cab said, most people tighten PV's too loose and jets too tight

Pv torque= 100 inch/lbs (not foot/lbs).

I tighte my power valve while holding the metering block in my hand with the jets pointed up as well. And I make sure it is good and snug and then I go 1/4 of a turn past that. I know the power valve is tight and I know the gasket is seated against the metering block correctly.
I will check it tonight to see if it is moving back and forth as described, I will swap out the orange pump cam for a white one and I will try the .033 squirters instead of the .035's and see what happens. I know this engine likes a relatively large pump shot because I am running a 2 inch 4 hole spacer.
I am going to pull all my plugs this evening and see if any of them are fouled. And If there is then I'm switching plugs, I have a brand new set of ngk v-power zfr5f11's and they are slightly longer then the ngk bkr5e's I'm running right now. Maybe the longer plugs will help burn the mixture better. Still wont see the .030 ifr's an .075 iab's until tomorrow.

The engine may have liked the orange pump cam because of the .025/.028 IFR's. It helped cover the lean spot.

Well I put the white pump cam on in the number one position and I put the normal accelerator pump nozzle screw in and then I put the .033 accelerator pump nozzle in place of the .035 nozzle.
I took all my plugs out and cylinder 6 and cylinder 7 were beginning to develop some black sooty looking sutuff on them but I don't think they were quite fouled, but they were close to being fouled.
I went ahead and installed the longer ngk plugs, fired it up and I reset the idle mixture screws to the highest vaccum reading with the transmission in drive and the tires blocked. I drove it around and there are no stumbles anywhere, so tomorrow I am going to put the .031 accelerator pump nozzle in and see what happens and I should be seeing the .030 ifr's and .075 iab's tomorrow.

YO7 you were correct the accelerator pump cam and nozzle is what was making the black smoke, I switched to the .031 accelerator pump nozzle from the .033 tonight and stayed with the white pump cam in the number 1 position and there is no more lack smoke when you hit the throttle.
My .030 ifr's and .075 iab's arrived today, I decided to leave the .031 ifr's in but I did install the .075 iab's and that made it to where all 4 mixture screws are at about 1 to 1.25 turns out. I lowered both floats to where you can barely see the fuel hovering at the bottom of the sight glass with it idling. I re-set the idle mixture screws to best vaccum with transmission in drive and tires blocked.
THe float level being too high and the accelerator pump nozzle and cam being too rich is the only thing I can think of that was fouling plugs? Or maybe they didn't run hot enough? I don't know. I have a hard time thinking the 64 main jets I am running are too big and were the cause of it. I will run it this way for a few days and I will pull the new plugs to see what they look like after a few days of run time on them.

If you get the mixture, jetting, near correct for your altitude and fuel those spark plugs should clean themselves up Let us know what you fnd out

Well everything appeared to be going well with the .031 ifr's and the .075 iab's and the new longer ngk plugs until this afternoon. I fired it up for the first time today and the choke/fast idle was on and while the fast idle was on it started making some loud popping noise out the exhaust again, sounding like it's too lean.
How could it be doing this today but not doing it the last couple of days? This thing is driving me nuts. I have had the choke/fast idle on before over the last couple of days and it sounded great and normal, then today it sounds like crap and is popping, wth is up with that?

So I let the engine sit for about 3 1/2 hours to let cool back down completely, then I changed the .075 idle air bleeds to .070 idle air bleeds and I fired it up with the choke and fast idle on and it's not popping out the exhaust anymore. Is it possible that .005 change in the idle air bleed was just enough to tip it over the edge on the lean side?

.005" times four IAB's. I would guess that the .070's are your leanest limit. I would suggest going down another .005" each to be safe. You will need to reset your metering screws again.

Well I have some .065 iab's and some .063 iab's. I also have some .032 and .033 ifr's. Should I put the .065 iab's in or change out the .031 ifr's for some .032 ifr's. The iab would obviously be easier to change. Do you still think I should put bigger ifr's in it? Bigger then the .031s?

Remember, one change at a time. I would test the .065's first and then the .063's if required. If you need to go richer after that, then open up the carb and change the IFR's.
Good luck with the O2 purchase.

Well I discovered something a little starnge. If you let the engine sit for around 6 hours or more and fire it up with the choke on and the fast idle on it starts popping out the exhaust and sounding lean again. I just fired it up about 10 minutes ago and it's dark out, so I decided to pop the hood while it was idling on the fast idle and my hedders are still glowing red! I grabbed a screwdriver and I turned the idle mixture screws out about 1/4 turn each and it made the red go away a little bit on the hedders but they were still glowing red.
How in the hell can .031 idle feed restrictors and .065 idle air bleeds be too lean on this engine? especially at 4000 feet above sea level, I was under the impression that when your 4000 feet above sea level your carburetor will run richer. The only other thing I can think of that's contributing to this lean condition on the fast idle I my 2 inch 4 hole carburetor spacer. Is it possible this spacer has leaned that circuit down because it's such a big spacer? I have some .032 idle feed restrictors and some .033 idle feed restrictors. So I am going to put the .033 idle feed restrictors in it tomorrow and see if that takes care of this issue. One thing that I don't understand is if you have already ran the engine and then fire it up with the choke and fast idle on it doesn't pop out the exhaust and sound lean, it only does it if its sat for at least 6 hours or more. Whats up with that? And is .031 idle feed restrictors and .065 idle air bleeds a lean combonation for the idle and off idle circuit?

At 4200 ft above sea level I usually start out with .075 or .080 IAB's in the Quickfuel stuff. The cars I tune will idle until they run out of gas or eat a roller lifter wheel due to lack of oil. If you want a specific set of bleeds checked for accuracy find someone with a minus pin gauge set. I have had stuff come in the incorrect packaging a few times.

YO7 what idle air bleed do you suggest I try when I install the .033 idle feed restrictors? I have .075's and .072's and .70's and .065's and .063's. I sure hope the .033 idle feed restrictors will be big enough to solve this issue cause that's the biggest set of idle feed restrictors I have.

I just read that an overly rich condition can make the hedders glow red as well. So this is ether because of a rich condition or a lean condition. It's not a timing issue I know that for certain. This is driving me insane I cant wait to get a wideband on this thing.

You have already told us that going from .025 IFR's to .028, and then to .031's the popping got better. I would suggest to keep the richer .065's in there and test the .033's. IAB's are easy to change so you can lean it out if it needs it. You have a good selection of IAB's to tune it.

You and I both run the FBO dizzy (setup for manifold vacuum = 30-32'ish degrees of timing at idle in D). This extra timing requires extra fuel to feed it on the idle/transition (IFR's/IAB's) circuit.
The first tuning change that I made after installing the FBO dizzy, was to richen up the idle circuit to make the A/F mixture richer at idle and low speed cruise (up to 50mph or so due to the vacuum advance too).

Well I don't know what to think anymore. I installed the .033 idle feed restrictors along with the .065 idle air bleeds. Fired it up with the fast idle on and it's still popping out the exhaust.
I'm starting to wonder if this is all happening due to an overly rich condition.
Because I have had problems with plugs fouling, and I did some re-search on this issue last night and a lot of people say that when your hedders glow red with the engine un-loaded sitting at fast idle it's because there is excess fuel and it's burning inside the hedders. I don't know how to figure out what the hell is going on. If it was a lean condition you'd think going up 8 sizes on the idle feed restrictors would take care of it.

There has to be a way to determine wether or not this issue is because of something being too rich or too lean. Other then buying a wideband right?

So you had glowing headers on .033, .031, .028 & .025 IFR's!! (I edited this due to the next response)


EDIT:
Question for other members:
Could an intake leak on that side of the engine cause the headers to be red?
Could an intake leak cause the popping sound out the exhaust too?

yes hedders were glowing with the .025 ifr's too.
There is no vaccum leaks anywhere, I have checked for that.
I also had 2 fouled plugs when running the .025 ifr's as well.
I ordered 4 .020 ifr's and when they get here I will install them and see what happens, probly wont see them for a few days. But if it still does this with the .020 ifr's then I'm throwing in the towel and spending the money on a wideband. I just cant really afford it right now, that's why I am trying to figure this out without spending the money on a wideband. But like I said if it still does it with .020 ifr's in it then I will just spend the money for a good innovate wideband.

My spacer is flat and true on both sides too because I put it on a flat piece of glass with some sand paper and I sanded it in a figure 8 motion until it was completely flat and true. And I am running the nicer superformance carburetor gaskets and my carburetor is torqued down correctly.

I received the .020 idle feed restrictors this afternoon. I installed them and put the carb back together, only now it wont idle on it's own I think I put a metering block gasket on wrong or crooked.
But I did hold the throttle steady at about 2500 rpm and I watched the hedders and they started to glow red again. Before doing that I took all my plugs out and I had 2 fouled plugs.
So I put 2 new plugs in it tonight. I will tear into it tomorrow and try to figure out why it wont idle, I am 90 percent sure it has something to do with a metering block gasket blocking something off because they came off with the metering block and I had to put them back on in the dark with a flash light.
I have been wondering and I don't know if this is possible but I think it might be, do you think my high speed air bleeds are too small and that is allowin the mains to come on faster then they should? and do you think that could contribute to the extremely rich mixture I have at fast idle? That's the only other thing I can think of, unless .020 idle feed restrictors are too big. But that's the smalles idle feed restrictor quick fuel sells.

""unless .020 idle feed restrictors are too big. But that's the smalles idle feed restrictor quick fuel sells""
""I received the .020 idle feed restrictors this afternoon. I installed them/now it wont idle on it's own/But I did hold the throttle steady at about 2500 rpm and I watched the hedders and they started to glow red again.""
""Before doing that I took all my plugs out and I had 2 fouled plugs.""
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Which side is the header glowing red, or is it both sides?
Which cylinders have the fouled plugs? Is it always the same locations?
I think that there is a reason why QF does not sell any IFR's below .020.

Since you have used .020-.033 IFR's and you are still getting glowing header(s) at 2500rpms (while using 64 main jets), I am leaning towards the issues that you are having are not carb related.
You might start a new thread asking about your glowing headers at 2500rpms. If you have a leaking intake gasket (between the head and the intake), this could cause the intake to be sucking in air causing a lean condition (red header(s)). This same issue could cause the exhaust to pop and also certain plugs to be "oil-fouled" (not fuel fouled). I just suggest that you take a step back and make sure that there is nothing besides the carb that could be causing the glowing header issue.

Are the fouled plugs always the same cylinders? If so, maybe you have bad spark plugs wires that are not firing which could cause those cylinders to be filling with fuel causing the red headers. The bad wires could also cause the popping out the exhaust too. Ohm out the wires on the cylinders which you are finding the fouled plugs to see what they measure.

Your earlier post stated your timing is 15* initial plus you have constant vacuum hooked to the vac advance giving you 30* at idle. That is too much timing and is probably the cause of your popping at idle, not a lean mixture. Remove the vac source and plug it so your back to 15* initial and see if your idle popping stops. 20* timing at idle is max for any small block and a mild cam like yours is more like 15*.

No it is not the same plugs that are becoming fouled. And they are not oil fouled, they are fuel fouled, They look just like the inside of a chimney. Normally there is a plug fouled on each side. Both sides of the hedders are glowing, mainly the 2 middle pipes on each hedder.
The plugs that were fouled yesterday were plug 6 and plug 7.
I removed all of my plug wires and they all ohm out at 40 ohms of resistance per foot, I jut got these plug wires for Christmas and they have maybe 500 miles on them, MAYBE.
Tonight I am going to take out the high speed air bleeds and start it and let it idle on the fast idle circuit and see what happens. If they still light up I will remove the vaccum advance from the manifold source and put it on the ported source, altho I don't see how this could cause the hedders to glow, at 2000 to 2500 rpm the distributer is going to see the same amount of vaccum from the manifold port and ported port on the carb.
If it still does it after this I'm going to buy a wideband even though I really cant afford it and wait until I get it and then I will get it hooked up and i'll be able to tell you guys what the wideband says the mixture is.
I really think this is fuel related, the plugs look black and sooty just like the inside of a chimney looks like. I did another compression test with the engine warm and ignition dis-abled and the carb all the way open and every cylinder reads 150 psi.
If the high speed air bleeds aren't the cause of this then I give up and will get a wideband. I am starting to think that maybe the high speed air bleeds are allowing the mains to come inn to soon which is adding fuel to the idle circuit while it's idling on the fast idle. I have read that the .028 high speed air bleeds are actually quite small and make the mains come on pretty quick. I'm going to put smaller main jets in and see if that changes anything too, if it does then that might indicate that the high speed air bleeds are coming on too soon.
I have checked for vaccum leaks, I can not find one. All of my vaccum lines are brand new, my intake manifold gasket is brand new and my intake manifold is brand new and I checked it for flatness with a straight edge. I have sprayed carb cleaner with the engine idling all around the intake manifold and the carburetor and I don't hear a change in the idle.

I agree that the .028 HSAB's are fairly rich! Mine came stock with .033's. I now run .033/.036's. It sounds like you have checked everything else out! Let us know what you find with the leaner bleeds and just test the bleeds first before swapping jets. Keep it at one change at a time so you know for sure what makes a difference.

Iv'e come to the conclusion that my engine wont idle with the .020 idle feed restrictors.
I have to sit there and keep it running with the gas pedal, it will not idle. And I took both metering blocks off and put the gaskets back on perfectly and put the metering blocks back on perfectly and it wont idle on it's own.
And I noticed the hedders were still glowing red with the .020 idle feed restrictors last night when I was keeping it running at 2500 rpm, I had to hood popped and my door open and I stood up and looked at the hedders and they were still glowing! so I think this is something else, not the idle circuit.
The only other thing I can think of are high speed bleeds and or main jets. So I am thinking tonight I will put the .030 idle feed restrictors in it that I had bought a few days ago along with the .075 idle air bleeds. And see what happens.
My guess is that this combo will let it idle on it's own and I will re-set the idle mixture screw to best vaccum in drive with tires blocked. Then I will remove the high speed bleeds which will delay when the main circuit kicks inn and see what happens from there.

if it does turn out being the high speed air bleeds which size should I try to run YO7? I was thinking maybe .030's or .031's.

You found that the .020's are way too lean if you could not keep it idling. Good test.
There is not much difference between the .030's and the .031's. I would say just pick one.
I think you found that it idled fairly well on .065 IAB's. If so, then I would go with that.
Lets say that you test the .030 IFR's and the .065 IAB's. If this idles well, then start with changing the HSAB's. Get it idling again first at your normal idle rpm, then move on to leaning out the HSAB's.h
Lets say that the .028 HSAB's are too rich which are bringing on your mains too soon. This may be what is causing the rich condition (as long as the plug wires are good, there are no vacuum or intake leaks). I would make a guess at low to mid 30's on the HSAB's for your test.
You just need to keep testing!

Note: My .033 HSAB's bring my mains in right around the 2500-2700rpm range. Remember that the main jets and the MAB's are a team and they work together. One could be fine while the other could be off. I would suggest leave the 64's in there and lean out the .028's.

Ok I'm feeling very optimistic right now, I'm just waiting for it to get dark to see if removing the high speed air bleeds fixes this issue. I don't have any high speed air bleeds to test with, so removing them is all I can do at the moment. But I installed the .030 idle feed restrictors along with the .075 idle air bleeds. I fired it up and it would idle on it's own now. The .020 idle feed restrictors were obviously way too small because it would not run on it's own.
With the .030 ifr's and .075 iab's I set the mixture screws to the best vaccum reading with the transmission in drive and the tires blocked. After that I hit the throttle a few times and I found that it cut out and felt and sounded a little lean right around 1500 to 2000 rpm. So I took the .075 iab's out and I put some .070 iab's inn and re-set the idle mixture screws to the best vaccum reading in drive with tires blocked, this came out to be exactly 1 turn out on each mixture screw. I hit the throttle a few times and it didn't sound lean and didn't cut out. So I think the ifr's and iab's are real close. Then I gave it some throttle while watching the boosters with my air cleaner off and I noticed that the boosters start to drip fuel pretty fast, I'd say around 2000 to 2200 rpm. And that's when it starts loading up and popping and when that is happening I can feel the heat coming from the hedders. So I hope I am correct in thinking that the high speed bleeds were too small allowing the mains to come on way too soon. It should be dark in about an hour and I will go out and see what it does with the high speed bleeds removed.

I am extremely happy to announce that I found the culprit to the overly rich mixture at fast idle, from 1500 rpm to 2500 rpm. It was indeed the high speed air bleeds, for the most part. I removed all 4 high speed air bleeds and waited until it got dark. Fired it up with the choke/fast idle on and I let it idle for about 5 minutes on the fast idle. I heard a few faint pops out the exhaust here and there, but nothing compared to how it was before. I decided to look at the hedders after about 5 minutes of it idling on the fast idle.
On the drivers side nothing was glowing at all, on the passenger side the two last hedder pipes running off of cylinder 6 and 8 were slightly showing a little bit of red, it wasn't glowing bright orange like it was when the high speed bleeds were in place, but you could see a little red, not glowing, but you could see it. So that leads me to believe the idle circuit is a little on the rich side with the .030 idle feed restrictors and the .070 idle air bleeds.
I was thinking I would order one more .028 idle feed restrictor because I have 3 .028 idle feed restrictors I broke the fourth one. And some .033 and some .035 high speed air bleeds. Then I was thinking when that arrived I would install all four .028 idle feed restrictors along with the .070 idle air bleeds and then install the .033 high speed bleeds and see what that does.
With the high speed bleeds completely removed, I had to of been idling strictly on the idle feed restrictors and the idle air bleeds tonight with it on the fast idle, and for 2 of the hedder pipes on cylinder 6 and 8 to slightly light up red shows me I have the idle mixture a tad too rich. So I think going with the .028 idle feed restrictors and the bigger .033 high speed air bleeds is a step in the right direction. I will also check my plugs before firing it up again to make sure I didn't foul any. I only ran it for about 10 minutes total today, but it doesn't take much to foul a plug in my expierence.

Good job testing!

Now you may want to test something that was mentioned by Jeremiah:
""At 4200 ft above sea level I usually start out with .075 or .080 IAB's in the Quickfuel stuff.""

Your IAB's will affect the A/F ratio way up into after the main circuit is starting in. If you have some larger IAB's or you have some drill bits, I would test the above statement. You could just put some larger IAB's up on the Primary side for testing if you only want to drill out a pair. Then if it works, then drill out a second pair for the secondary side.
I would suggest leaving in the .030 IFR's and start testing with the larger IAB's. If it starts good, and it gets rid of the glowing headers, then you are doing the same as if you were swapping in smaller IFRS. As long as your metering screws don't get too far out with the larger IAB's, you should be fine.

It would still be a good idea to buy the .036/.039ish sizes of MAB's for your testing too. You could also test with some smaller main jets than your current 64's since you found removing the MAB's leaned out the issue.

Nice job! You have put in allot of effort to try and figure this out. Some people would have just bought another carb instead of blaming their own lack of effort. Since you are at a much higher altitude than most, you have a little extra hurdle to jump.
I just hope you are keeping good notes! You will be flying through this tuning crapt once you get your wideband kit one day.

well like I sad I'm fighting this fight at 1500 to 2500 rpm because my plugs were fouling out so quickly. And when you have it on the fast idle just as the choke opens and you can hear it popping and banging out the exhaust and when you pop the hood at night and see your hedders glowing that's whats got me fighting this fight with this thing.
I did install the .075 idle air bleeds with the .030 idle feed restrictors and it caused a little bit of a lean spot around 1500 rpm. that's why I went down to .070 on the idle air bleeds. But I will put the .075 idle air bleeds back in it tonight and see if that makes the last 2 hedders pipes not light up at all.

What size drill bit would I need to drill out the .028 high speed air bleeds to .033's? Does anyone know? I'm inpatient and don't want to wait 3 days for the bleeds to arrive that I ordered yesterday.

I need a drill bit size 66 to make a .033 high speed air bleed. which of course I don't have and neither does any of the part stores or hardware stores in my area. The smallest drill bit I have is a .059, I measured it with my digital calipers and it comes out to .039
So I can make .039 high speed bleeds. Which will probly be too lean, but I was thinking if I jetted up the primary jets to 65's it might be ok. I have some 65 main jets I could put in there. And I could take it for a test run this way and see if there is any issues.
I just wish I could get the .033 and .035 high speed bleeds I ordered faster.

Definitely test the .039 HSAB's but don't sweat changing from the 64 to 65 jets (just yet).
ONE CHANGE AT A TIME!

Note: I don't think that they would be too lean in your case. I swap back and fourth from .036 to .039's on my secondaries as the outside temps change to tune my WOT A/F readings.

McMasterCarr.com is your friend. They have drill bits in all of the small sizes that you will need. I bought a dozen or so from them so that I could drill out my IFR's/IAB's/ and MAB's.
http://www.mcmaster.com/#standard-drill-bits/=t0eh03

well I had the 63 main jets in it, So I drilled out the .028 high speed bleeds to .039 on all 4. I installed the .075 idle air bleeds and re-set idle mixture screws to best vaccum reading with transmission in drive and tires blocked. I installed the 65 main jets because I was worried the .039 high speed bleeds would be too lean.
once I got it warmed up I opened the throttle while I was under the hood with the air cleaner off and I seen fuel start to drip from the boosters at about 2200 rpm, And before with the .028 high speed bleeds it seemed like it was coming inn at around 1600 to 1800 rpm.
So my set up is this, 65 main jets, 74 secondary jets. .030 idle feed restrictors and .075 idle air bleeds. ,039 high speed bleeds. .031 accelerator pump nozzle, white pump cam on number one setting. Float level is at bottom of sight glass when engine is running. All 4 mixture screws are about 1.25 turns out from fully seated.
So hopefully this is close, I'm going to take it for a drive tonight and see how it feels. Oh and I took all my plugs out again to check them and plug number 5 had some black sooty looking stuff on the plug but it wasn't fouled. So I have 8 fresh plugs in it gapped at .045

Make sure to get us an update!

well I drove it around last night and I didn't really know what to think. It seemed to be a little lean in that spot of the throttle between the idle circuit/ main circuit. I noticed I had to give it quite a bit more throttle to take off when pulling out on the highway.
I'm sure this is due to the delay in the mains coming inn because of the larger high speed bleeds. While cruising around town on the idle circuit it felt pretty good, I think the .075 idle air bleeds might be a little too big. The idle air bleed controls how fast the fuel flows thru the idle circuit and the idle feed restrictors control how much correct? I think I'm in need of the .028 ifr's that I ordered. Because like I said with the high speed bleeds completely removed and with the engine idling on the fast idle circuit the last 2 hedders pipes by cylinder 6 and 8 were slightly showing a little red. So I think .028 ifr's will eliminate the hedders lighting up at all and I have some smaller .065 and some .063 idle air bleeds to work with once I install the .028 ifr's.