950 too rich at cruise

Another "my 950 is too rich" thread. I've posted on RFS but not gotten much response there.

Anyhow, I recently bought one for my 451 (from a carb guy who used to be on here, and we are talking on RFS) but I'm considering sending it back and I eat $50 plus shipping. (1.45" venturi, Holley ultra baseplate, and I think a Proform body, billet metering blocks, Ultra fuel bowls with sight glass).

It seems to be untuneable for efficient street use with my combo (451, 272@.050 mushroom cam)- just too rich at cruise and part throttle, which is where a street driven car spends most of its time. Too bad, because it feels great for driveability and really hauls ass when I hit the secondaries that I haven't even tuned yet.

The problem (many threads I've found by Googling, including on here) is that it's big enough that I have to run on the t-slots, even at 60 mph, 3000 rpm. And the 15" cruise vacuum sucks harder on the slot than the 8" idle vacuum... 13.8-14.0 at idle with screws out about 1-1/4 turns. 5.5 PV, 77/86 jets.

With the 950, I can see richer than 11:1 at the very top of the t-slot at low load and below 2000 rpm where the mains start to come in! Which is exactly the point where I'm putting around at 30 mph.

I went back and read my earlier posts on RFS about my 4780-2 that I converted to replaceable brass and a 4-corner idle with QF 12-700 baseplate. Although the same problem exists (12:1 at top of t-slot), it cruises at 14:1 or better and that is ok). I can't get this carb to do better than 12.5 low speed and (maybe) 13 at 3000 rpm.

I've gone all the way down to .045 primary TSR, and .031 IFR, .082 PIAB. And it STILL runs 11.5-12:1 at the top of the t-slots below 1800 rpm, but 16:1 lean at tip-in (no flat spot yet but I probably can't go much leaner before I can feel it). Last ditch will be to take the IFR down even a little more, maybe .029 or .030.

My 4-corner (and replaceable brass) conversion on the old 800 4780-2 works better than this - I tweaked some more and can cruise at 15.5:1... although there is a slight flat spot at tip-in I can live with.

So - I think I'm trying to do the impossible with a big cam (decent street manners and fuel mileage when my foot's not in it, and lots of top end horsepower).
I want a big 4150 carb but don't want to cruise on the t-slots.

Is there some way to make the t-slots smaller (or even tapered) that won't break the bank? I don't have the talent to try that.
Thanks for any help.

You know what’s coming next, right?

seems like it shouldn't even run with a .045" transfer slot restrictor. when you say tsr you mean you tapped the body of the carb to screw brass in the transfer slot feed?

the PIAB and IFR seem pretty far off too, but ikd.

do you have a baseline you can go back to?
seems most people use a TSR of about .080", IFR around .036" and idle bleed around .070 for baseline on those carbs.
Also I don't think you should try to get accurate air fuel mix readings at idle, especially with a cam that large.

Yes, main body tapped for TSR.

As delivered it had: .070 IAB, .033 IFR, .081 TSR. Sounds reasonable but runs pig-rich (12:1 at tip-in, 10.5 on full t-slot)! Stinky idle too. No point in going back to what obviously doesn't work

First I tried going up on the IAB, that made little change as expected. Then going down on the TSR in steps which helps some. Now it's lean at tip-in and still 11.5 on full t-slot.
This problem exists on the old 4780-2 also, but less severe since it takes a bit more throttle to cruise with the smaller venturis and butterflies.

Sure, I am aware of misfires causing artificially lean readings due to unreacted oxygen in the exhaust.
Whatever the actual AFR is, I set the mixture screws for best idle which always turns out to be 13.8 on the meter and no eye-watering exhaust.

No... what?

Yep, that is a common problem with Holley type carbs.

Step up the high bleeds .002-.004.......And a .033 ifr is WAY small for that size carb.....

OK thanks, I will try that today
Why is the IFR considered way small, if the idle screws are out just over 1 turn? Doesn't it take the same amount of fuel to idle the engine, big carb or small

Probably for someone to tell you swap to efi. 😄

AndyF has a (frequently made) point, but I wanted a simple old-school setup, AND I don't feel like plowing another 2 grand into EFI (and doing all the associated fabrication). It would be nice to be able to tune from a laptop instead of: drain bowls, remove fuel line and four bolts, remove jet/bleed, drill a new one, installation is the reverse of disassembly! I've already had a "helpful" person tell me to get a smaller cam, too

I tried going up to .033 on the primary MAB. Not sure if it helped (no dramatic difference). Cruise at 3000 rpm, 15" Hg still 12.5:1, and accelerating moderately (10" Hg) still 14:1. There is a lean flat spot at tip-in that I don't usually hit anyway, but 30 mph 2000 rpm cruise is 15:1

Also I leaned out the idle screws 1/4 turn to an indicated 14.5-15:1... same vacuum and RPM, and I don't think any lumpier, so that was probably too rich also.

Might try enlarging the MAB some more, say .036 and see what that does. I really want to get the 3000 rpm cruise as lean as possible (like the 14-15 with my 800).

Wanting to have excellent street manners and race car performance is a difficult goal to accomplish.
When you start making compromises or concessions to one , the other will suffer.
My " street " toy is a 12.85 :1 , E-85 swilling solid roller and carburetor having bundle of joy.
There are some driveability issues that I live with , because when I push my right foot down with enthusiasm , I quickly forget that little stumble on tip in.
You can get them close , but I have yet to see perfect.

you know what you want, correct
Keep working on that problem, part throttle cruise to rich at 3000 RPM, until you get it the way you want it and then work on other parts
You can do this, sneak up on a little at a time until your happy

The ifr's have a big impact coming up on transition/tip in and too small will give you that lean stumble you talked about earlier as you open the blades so we have to find a balance for idle and transition with idle bleeds, t-slot exposure on BOTH front and rear blades, float level, timing, etc and the hi bleeds will definitely control the cruise all the way up to max rpm's, I do it daily and the results are eye opening.....

my 2 cents . You have quite a cam in a sort of small motor . With overlap it will be awkward .
T slot jet is too small .T slot and iab work in conjunction , increase or decrease together What size idle feed restrictor as this will affect idle and off idle . What powervalve ?
A long time ago a smart man told me - dont fixate on the afr number give it what it wants .
Example my cruise , 25/2900 is 13.4 any leaner and it surges .Peak hp is at 12.9
granted i run a 1050 now but all holley are same principal . When i used the 1000HP on my 505 i had to adjust the same to get it to run as good as it had on the 440 .

Tex

With the original .081" TSR the top of the t-slot was pig rich (10.5)...
IFR .031, PV 5.5.
Eventually I will put in smaller main jets, a 9.5 PV and enlarge the PVCR (.059") as needed.



If I ignore the AFR number then I'll have to stop at even MORE gas stations and buy stock in Champion or Autolite... with a highway cruise AFR of 14.5-15:1 I was still only getting 9.2 mpg at a steady 60 mph. (3.91 gears, no OD).
This carb felt great as-delivered but was stinky rich at idle and everywhere else.
I've never had a lean surge at cruise even as high as 15.5:1 and didn't bother pushing it any higher.

i get the fuel consumption .
just keep working at it . But think each circuit and then how it interrelates to the next .
Im not a luddite but carbs work pretty good and will rarely let you down on the side of the road .
oh i probably wouldnt be using a 9.5 power valve .
that is way high ! I run a 6 or 6.5 , factory is 4.5 . But i have a very large converter and hence not much load at cruise but high vacuum . My vacuum @ idle is 4 or something close . With a lower PV say 6 or 5 whatever you will find at cruise you are on the jet but pv is closed and will clean up

Tex

Thanks. Since my cruise vacuum is 15" and I want to use small main jets, I'll need the PV to kick in sooner than usual as I get on the throttle.
The car is already accelerating briskly from 3000 rpm at 10" (and at 40% throttle where the secondaries start to open, there is still 6").

9.5 might be a little high (I run an 8.5 in the old 800 carb). But unless I can get a sufficiently lean highway cruise by dialing in the main air bleeds, (which will require reducing the main jets too), I don't think the 5.5 PV that's in there now will open soon enough.

Anyhow I have to get the overrich 3000 rpm cruise sorted before I worry about more enrichment for WOT

Try using all three circuits that are feeding fuel to your motor at light part throttle cruise, idle fuel passages, all 4, transition fuel feed circuits on both primaries passages and the main jet jet size as well Maybe throw in the idle air bleed size on both primary barrels also by opening them up a little tiny bit, .0010 to .0045 Not a bunch

What do you mean, use all three circuits? Isn't that normal operation...

My low-speed part throttle is now sufficiently lean, as previously noted. The remaining problem is at higher rpm part throttle where the mains are also flowing... I've been reading up on emulsion bleed tuning and may eventually have to start playing with those (fewer/smaller emulsion bleeds to reduce the contribution from the mains at lower flows, which is what I need). Current setup from top to bottom is .028, plug, .028, plug.

I am not sure yet that the MABs are now too big (will also tend to lean it at high RPM), will be interesting to see how it runs with the .036. Can always go back to .033 or .030.

Dom had me plug my top emulsion hole to get the mains in quicker. It helped. I can cruise in the 14s now, but do have a slight lean hesitation at the top of the slots just as the mains come in. Lesser of 2 evils. It is only at light throttle up. A quick stab runs past it with the help of a big 50cc pump shot. Just have to drive it the way it runs best even if it is not the way I would particularly like to.

The transitions from idle to power circuits and then the cruise circuit all want to occupy the same throttle position. And all want different fuel ratios. A compromise is the best you will probably be able to achieve with some draw backs.

I always run 9.5 or 10.5 PVs. Mine have always wanted a lot of fuel quickly after being a bit lean in the transition to the power circuit.

I guess my theory is to have it a bit lean on the slot to get a decent cruise and then overcompensate a bit with a big acc shot and early PV opening. Not a perfect solution, but it works pretty good. At least for me.

This textbook picture (from the RFS emulsion tuning sticky) makes interesting reading. So I may want fewer holes to reduce the low-flow mains... assuming it's the lower of the two active bleeds. Could plug that one and see how it changes!

I have been concentrating on the t-slot thinking the problem was solely a slot that's too big, which is certainly part of it.
But even with a .045 TSR it still gets too rich sometimes (and too lean at others).
Now I'm thinking part of my problem is too-big main jets that start to come in (while still on the t-slot too) but lean out at higher rpm and larger throttle opening...
Which is just what I'm seeing (12.5 at 3000 rpm, 15", and 14.0 at 3000+ rpm, 10").

So going bigger on the MAB was likely the wrong thing to do!
Dropping the main jets several sizes and decreasing the MAB would reduce that contribution at low throttle openings, and it would get richer with more flow. (Then increase the PVCR as needed to maintain AFR at wide-open primary.

If THAT doesn't work, then I can start on the emulsion bleeds... thoughts?

If you have 15 inches of vacuum at cruise you NEED a 10.5 power valve. Opening the PV as late as you are puts a hole in the fuel curve just like you are getting and you have to cover it somehow.

In other words, because the PV is opening so late, you can’t cut the T slot back far enough to clean it up. Open the PV sooner and let it do it’s job and you should be able to take some fuel away from the T slots and lean it up.

Unless I’m missing something that’s what I see.

That was my plan once I got the t-slot + mains cleaned up (an earlier-opening PV and probably larger PVCR).
As I just posted, I think it's time to make the main jet smaller, and I messed up on the MAB and should've made it smaller too so it won't lean out as much with larger throttle openings.

But you're right that I'll absolutely need an earlier-opening PV especially if I reduce the main jet, since that would make the curve hole worse. I have a 9.5 handy so I'll try that first.

"Light acceleration" is a relative term with this setup in street use. Even at 10" vacuum, still on the primaries (less than 40% throttle with the progressive linkage), and in 4th gear, it accelerates quite promptly when starting at 3000 where the cam is just coming into the start of the powerband.

I hate to change multiple things at once, but I'll probably wear out the main body threads before I get all this sorted one change at a time!

OK, so: drop PMJ from 77 to 74(?); change PV to 9.5; then reduce MAB to .030 or even .028. Not sure about the .059 PVCR yet but I know they're bigger on my old 800.
How's that sound?

I would like to see you use a #75 jet size instead of going to the # 74

I’m not sure I would drop the MAB any and if you do make that change, I would do it after you make the other changes. The good news is the bowls don’t have to come off to do that!!!! If you reduce the size of the MAB you delay the booster coming on, and you will make the A/F ratio richer at higher RPM. So the bigger MAB has the opposite affect, which is a bigger MAB will get you on the booster sooner and lean the higher RPM.

The rest looks like what I would do.

agreed, i have one of these 1.45" 950 carbs and i went from 78 to 72 (expecting it to be lean) and ended up getting back up to 74 or 75 to get the cruise happy. stepped downleg boosters.
this is on a mile 360 with the normal stuff, headers, airgap intake, good compression and semi lumpy cam...

i would get the cruise jetting in the range needed then go back to try to fine tune the IFR and TSR and bleeds. i made a spreadsheet to calc what PV area i needed to get the whole primary side jetting area with the smaller jets to equal what it was with the baseline jets..

Sounds a lot like my setup except it's a 451 with a really lumpy cam



But the whole point is that I'm having trouble because cruise throttle position, even at 60 mph, is still on the transfer slots
So if I change the IFR, TSR, IAB then I've changed the cruise AFR too! That's why I started with the idle, then the transfer, then the cruise, and finally will deal with the PVCR. And then I can try the secondaries... although it's too darn fast to test full WOT safely on the street.

Anyway it's chilly this morning and I still haven't readjusted the clutch linkage, getting too old to lie on the cold driveway, so no test results yet.
(MAB still .036, #75 jets, 9.5" PV).

Krautrock, did you use a wideband AFR to tune your carb?

no wideband, just reading plugs. if the plugs stay clean and i can get the tune good enough that it drives well in all areas of throttle openings then i'm happy.

Tune the car to run well. Use the O2 meter for information, not final decision making.

Don't lean to heavly on the O2 meter for idle information with a big cam. Remember what it is reading, its not air to fuel ratio.

Yes, I even addressed this several posts ago:



The car ran very well when I put the carb on with the initial tune. The problem is that it was pig rich, wasting gas and darkening plugs.
Hence my struggle to get it leaner on the meter AND running well. The butt-dyno isn't sensitive enough and the nearest strip is 90 miles away...

More (confusing) results.

With #75 main, 9.5" PV, .036 primary MAB, .082 IAB, .031 IFR it may be a little leaner but still runs rich at 60 mph/3000 rpm/15" Hg... I think - the gauge is fluctuating all over the place at that throttle opening - from around 12.2 to 13.8...

(From what I've read, that means the MAB is too big for the jets, and causing air bubbles?)

Light acceleration (holding 10") starting at 60 mph/3000, it climbs to about 14.5. That should be ok.
Power valve only makes a little difference (below 9.5"), doesn't look like even one full AFR. Needs significantly bigger PVCR with the smaller mains than the .059, as I surmised.

What's odd is that if I keep my foot in the primaries but not the secondaries, nearly half throttle (3" vac, up to 4000+ rpm) it gradually got richer as the rpm climbed until I was down around 12.5.
I think that means the large MAB is finally allowing more flow from the mains by 4000?

If I make the mains even smaller (#73 or #74) it will make the air bubbles worse - but smaller on the air bleed will also make the mains come in sooner which I'm trying to prevent!
I have not yet disconnected the secondary link so I can go full WOT on the primaries only.

I don't have enough road to continue 4th gear testing at high revs, high load (4000 is already 80 mph, and in lower gears it accelerates too fast to get a good reading).
What do I do next

Is this right? A smaller MAB delays the onset of boosters? I thought it'd be the other way around, a bigger air leak requiring more airflow to suck fuel through it.

Which brings up another question: Are small main jets and big PVCR affected less by the air bleed at high RPM (than a big jet with a small PVCR)? Or do they behave the same and only the total area is the factor that determines fuel flow?

I'm in over my head here

on the main bleed, as the air speed going into the horn starts to develop pressure. the bleed allows the pressure into the main well and that does the emulsion trick. the more emulsion and pressure, the quicker the fuel mix makes it's way to the booster.
so yes, larger air bleed makes the booster come on earlier.

Thanks! I will try going back to the .033 and .030 MAB and see how it behaves. At least that's the easiest to change
If I can just stay out of the boosters until the transition slot is nearly 100% engaged, my overrich cruise should get better... I hope.

It occurred to me that the AFR might be going richer at higher load/rpm because I only have the primary blades half-open or less, and 3" of vacuum.
So it's acting like a small two-barrel and it's being sucked on really hard

I could disconnect the secondaries and open the primaries to WOT. Bet it wouldn't be as rich at 4000+, and less vacuum too.

Krautrock answered it. Yes, the bigger MAB will make it richer down low and leaner up top. Which is what all Holleys I’ve played with have been lean down low and rich up top. Assbackwards from what it really should be.

Thanks... learn something new every day

Any ideas why my AFR reading is now "bouncing" at cruise?

Dr C what holley 950 do you have? The 830 cfm version? That's what I have and it acts the same way. I finally settled on 70 iab, 28 hsb .081 on the T slot. .031 ifr down low. Its better not perfect. What I need is more idle timing. Without locking out the dis. 34 total 24 initial.

You may be experiencing a case of CarburitisTweakisToomuchus.

Suggest going back to square one as delivered and making sure all is set up correctly. Based on who you bought it from, I would have to guess that the meeting blocks are set up in a pretty standard orientation and the IFR's are down low.

Maybe open up the IFR to .036 or .035 and begin the tuning one step at a time from original config. Idle slots not over exposed and base timing set to around 24-26 depending on what your motor likes at idle and floats set correctly.

Your AFR could be bouncing due to an exhaust leak somewhere, or your O2 sensor is shot/dirty.

Thanks. I agree that there are an awful lot of things to tweak, most of which interact! I may be chasing my tail, but I did start one step at a time

I'll go down the list:

Everything was set up correctly as delivered including IFR moved to low position- the problem is it was pig rich everywhere, worst at the top of the t-slots!
The idle screws are out only slightly over 1 turn with an IFR of .031 (primary) and I left the secondary alone at a pin-gauged .032, although I did plug the baseplate dribble holes.
T-slot exposure is just square on the primaries.
Secondaries are almost closed (butterflies have .100" holes in all four and I run a PCV valve).
Idle timing is 27. It could use even more but I don't want to overdo it while running vacuum advance, street driving and pump gas.
Float levels as described.

Maybe I wasn't clear - the AFR only bounces from low 12 to high 13 when I'm holding a steady 60 mph at 3000 rpm, 15" Hg. At idle it wanders a bit but that's low-rpm misfire from the overlap. During acceleration to 4000 rpm it was quite steady. So I'm thinking "spurts" due to the emulsion, or the large air bleeds?

Other than 2-bbl dirt carbs, you should NEVER need bypass air and no, that carb wasn't right as delivered imo especially with the "I don't know how to lean it out so let's drill holes in the bleeds" bs......

Interesting, thanks Dom!

I realize there are differences of opinion among tuners, but I'd have to open the secondaries into their t-slots to get enough air and most everything I've read/chatted with say not to do that (as the secondary slots are further up the bores).

I thought the blades came that way, not drilled by builder. The holes are not for leaning it out per se, but to pass sufficient idle air for the idle speed. This cam has lots of overlap and needs a surprising (to me) amount of air for its 1200 rpm idle. What is your carb & combo? I seem to recall you having an even bigger cam (276@.050)?

You've said that is OK to do, but won't that cause even more tuning difficulties by introducing yet another source of fuel?

Edited to add: these plates come that way from Holley/QF. The ones I'm not using (with 1/8" holes) are stamped "325" which is factory-made.

Close up the primary idle side a little and make up the difference on the sec side.

To take part in show-n-tell here (although not the same carb body):
440 with a 266@.050 and 6" Hg at idle.
Runs clean all through the rpm range and cruises in mid to high 14's from 2500 on up.
Total is around 36ish and running vac adv.
4.10 and 727.
Fuel pressure raised to just around 7psi. Using .120 N&S.
QF 1050AN body
Titan M-Blocks .026 E-Stack no siphon break.
PJ: 78
PVCR: .067
PV: 6.5
MAB: .26
IAB: .67
IFR: .036
Pro-Sys base plate and drilled throttle blades x4.

And I put in a FV178 PCV valve and it really helped my combo.

I've tried that too (backing off the primary to almost no t-slot)... didn't seem to make much difference. How big are your blade holes?

How come you only have 6" idle vacuum with a smaller cam than my 451? Idling real slow and lumpy? Or a flat-tappet (mine is a mushroom)?
What's special about the FV178 valve?

A major difference I see is that your MAB is much smaller (and your emulsion stack is smaller too)... .028 MAB is the next thing I'm planning to try.
Raining all through tonight, so no road testing today!

I think I am near 1/8th on the holes.

Pull carb off and set pri blades at .04 to .02 on exposure and do the same for sec side. Put it back on and see where it idles at when warm. Not just start up and T-stat opens up warm, but running for a while warm. Then adjust back the sec side and then to pri side in equal tweaks.

Manifold choice and cam specs (lobe sep angle) my be the difference here??? Bigger single plane (M1 4500 and 108).

The FV178 seems to be the can of choice for low vac motors. It's a GM piece speced out for their HP solid cammed mills. Not as simple as just walking into box store and grabbing a random PCV off of the display rack.

Mine idles at 1200-1300 free and drops down to 950 or so in gear. Still a little stinky at idle, but I'll live with the choice I made of running a bigger cam on the street.

It costs to be cool and there are some sacrifices that go with the cool factor.

That IS where my primary t-slot exposure is... and the secondaries are closed, because otherwise it idles too fast with the 4x .100" holes and the "grab whatever fits" PCV valve I'm running Fortunately I have a 4-speed and the idle is 1200+ anyway, so I don't have to worry about an in-gear drop.

I found an old Speedtalk thread (https://www.speed-talk.com/forum/viewtopic.php?t=2767) where the guy didn't like holes in the blades because that airflow comes past the boosters and tends to start them too early. Wonder if that's part of my problem... anyway he recommended bypass air without holes. Dom absolutely is against any bypass as you can see, above. Some others recommend turning off the secondary idle screws completely and just dealing with the primary idle circuit!

To have even more things to change, as if I wasn't up to my ass in alligators already, I ordered some non-drilled blades and a Fram FV178

Napa is your friend with the FV178 (P/N 29220). Just around $6.00

Re idle speed..that's the rub with holes in plates. Hard to go backwards if they are too large. I have used solder in the past to plug them up.

I found an article from Innovate: https://www.innovatemotorsports.com/resources/carb_EFI_mileage.php
They had the same problem I did (idle ok, but pig-rich on the t-slots).

On a 750 "Mighty Demon" they reduced the IFR from .036 all the way down to .020, IAB down to .032 and MAB up to a whopping .090. No mention of a TSR.

So their smallblock with a 253/259@.050 cam is on the idle circuit up to 2900 rpm and the mains start coming in at 2800.
That's way different from most of the tuning advice I see!

That article always loses me with their bleed and IFR sizing. They might be taking a different path to the same place, but it goes against everything the carb tuning gurus seem to follow and suggest on RFS.

I agree, I'm posting on RFS too. But it's hard to argue with the Innovate results That engine has a 9" idle vacuum.
And that was my biggest problem that started all this - idles fine, runs pig-rich at cruise. I went all the way down to a .041 TSR and it helped a lot, but also created a super-lean flat spot...

If I tried their approach, I would want a bit more idle fuel (doubt my combo would even run when off the mains with a .020 IFR!)

So rather than return to what I know didn't work (as-delivered), I'm thinking of something like this (along the unconventional lines of the article):

Original Current Proposed
IFR .033 .031 .029 - this is probably where I should have STARTED leaning, .031 helped but wasn't near enough
IAB .070 .082 .063
TSR .081 .041 .074 - even with .041 it's not right, so go back to a normal size
MAB .030 .082 .085 - want to delay the mains
MJ 79/88 75/86 75/86
PV 5.5" 9.5" 9.5" - cruise vac 15"
PVCR .059, will change last, probably .070 or so with the smaller PMJ

This old thread: https://board.moparts.org/ubbthread...48706/holley-rich-at-light-throttle.html
points out that it'll never be right when cruising on the t-slots, because the idle vacuum is less than the cruise vacuum... but I think I can get closer than it is.

What is most important to me is to drive at 60 mph without being overrich, also 25-30 mph - because that's where the car spends most of its time on the 8 mile drive to town, then cruising on the street.
Rough idle is a given with a 272 @.050 cam, and I can live with a little flat spot at small throttle settings.

I would suggest saving the 6 bucks and spending the money on the only tuneable PCV valve out there. And that’s the ME Wagner PCV valve. I have no idea of what the flow rates are of that Fram part number, but whatever it is, the absolute improbability of it being correct for a combination like yours is astronomical. I doubt Fram has anyone developing a PCV valve for applications like this because because any fixed orifice PCV valve that would work for you would never work for me. So they would literally be developing a part number to sell what?? maybe, maybe 5 of them for the entire country and it may work correctly on one application.

I can’t stress the importance of not only using a PCV valve but on using a tunable one. And Wagner makes the only one.

With your manifold vacuum at idle you can still use it in dual mode and it will change the tune up.

Just my .02 cents, but I use one and use one on any engine I do that has much more than a pretty mild street cam in it.

Worth every penny.

An .085 MAB a will not delay the mains. Don’t forget that the MAB feeds the emulsion stack too. So if you have an assload of emulsion (you don’t need it) the MAB has to be big enough to feed the emulsion bleeds and correct booster timing.

I’ll go read the link because I’m interested but that big MAB they used got the mains going earlier unless they have something else funky.

Yeah, the article specifically said they were delaying the mains with that big MAB and that is DEAD wrong. I need to click on the link to see the full article but a bigger MAB starts the flow to the boosters sooner and leans out the fuel curve at high RPM and the opposite happens with a smaller MAB.

I guess maybe that that big MAB could be killing any signal to the booster, but I’d have to think about it for a bit but that seems a queer w.any to do it if that’s what’s happening.

BTW, they still set power valve opening wrong. Damn, that lie won’t ever die.

The full article doesn't seem to be there (goes to the magazine site but it's a 404 error).

I agree that some of their explanations look hokey, and that PV vacuum is a crock but I ignored that. I know better

I am hoping to find a small enough IFR that it can't run so darn rich at cruise (15") but still have enough to the idle screws (8"). It will end up being a compromise, of course. Going all the way down to .041 TSR helped lean the cruise some but it also created a lean flat spot.

Then I can play with the air bleeds, IAB then MAB. Those are easy to change but I'm getting really tired of taking the bowls off!
Do you think .028 is small enough?

Well, if you are giving out Wagner PCV valves...I'll take one. However, spending $6.00 worked for me and no need to spend $130 for a PCV valve.

Yeah, that got my attention too...

Meanwhile I'm wondering if I can't just use a fixed orifice instead of a PCV valve?
At idle there's less vacuum (8"), so less air flow, and I need more air at 15" cruise vacuum anyway to help with the rich problem...

And another reason why baby carbs on hot motors suck, too peaky here, to sensitive there and why I'd put a proven Dommy on anything making over 500 hp and have for years with great results. Yes, my street cam is .680-.660 and 276-281 and idles and drives awesome with no issues anywhere in the power band BUT, it took time and patience to get there and yes, holes in blades are bypass air to smooth out rich idle/transition issues. I never said it's ok to drill blades in 4 barrels and I never do under any circumstances except like I said for high velocity 2-bbl dirt stuff.....

How's your AFR and vacuum at cruise? Can you get it above stoich, or at least 14:1?

I could go to a 4500 but then I'd also have to get a single-plane manifold to match... concerned about the effect on torque when not WOT (which is nearly all of the time)

Too big of a main bleed = no fuel through the jets needing HUGH jets up top to be happy which floods part throttle cruise when on the mains.....

Even with my t-ram square jetted w/no p/v's I can cruise at whatever afr's I want with ease and it's happy in the upper 13's to mid 14's and your dual plane is making matters worse imo.......

I tired a fixed orifice and opened it up a few times before ending and giving up at 0.110 and trying the 178. It ran/idled better with the 178 and the fixed went to the used parts bin.

The Wagner in single stage is just an adjustable flow control valve. Looking at the Wagner parts, I am guessing that the Idle screw is a 10-24 set screw. The instructions indicate that 3 turns is the max opening, which should be about 0.126.

Thanks for the tip. Too rich part-throttle cruise is my whole problem! But "up top" won't the secondaries be coming in too, and I can tune them leaner to compensate?

The Eddie RPM has a gap in the divider, not a 100% dual-plane. What would you recommend for a single-plane then? I'll probably put on the aluminum heads this winter (293.5 cfm at .600-up and also breathe better at lower lifts).

Thread some aluminum bolts into the carb mounting holes and cut them off flush. Then drill and tap new holes for the Dominator carb. You might have to open the plenum up some, but that's no big deal either. I have done this on several different intakes over the years. Works fine and costs about $10 for the aluminum bolts.

In my personal experience, I don't feel that the Dominator hurts the torque or drive-ability on the street once dialed in. I agree with Dominic that the Dominator carbs are the way to go on our hotter/bigger big blocks and Hemis. I have a 1050 Dominator with Dominic's metering blocks on my primarily street 540 Hemi. Drives great. On mine, the key was getting the mains to come in early enough (1,900 RPM +/-) so that I could keep the engine happy when on the slot, and then cruising on the mains in the mid 14s at that lower RPM .

You mean, keep the Performer RPM and put a Dominator on it? Sounds very unusual
I'm getting outside my original questions, which was: how to get the 950 to stop running overrich at cruise
If a single-plane is what will do it, I'm certainly willing to spend that much!

Did some testing this morning... As usual Dom is spot on (and madscientist too). I did get the t-slot lean enough for low speed cruising with .028 IFR, .074 TSR and .082 IAB. Have the screws out 1.5 turns in front and 2 turns in the rear with a bit of secondary air added to maintain 1200, 8", 14.5 idle.

But I popped in .080 PMAB for a trial - sure enough it leans out a lot on the highway as the revs climb (still only on the primaries) but it's too rich as the mains come in. At this point I agree with madsc. that I don't know what on earth the people in that Innovate-hosted article were thinking!

And the damn thing STILL wants to cruise (15", 3000) at 12.5 to maybe 13 at best! Fuel curve looks like a roller coaster. Craptastic. Although driveability is still good except for a too-lean spot at low rpm on the slot.

So my next move will be to go smaller on the MAB, actually below .030. Also drop the PMJ's from #75 one or two sizes, and try it again.

Progress!
I have some air bleed blanks on the way (Tues.) so I popped in the only small PMAB I had on hand, .026, and dropped the PMJ to 73.
Now it runs quite a bit leaner - cruise is up to 13.5 at 15" Hg, 3000 rpm (in 3rd gear). The .059 PVCR probably could be a bit bigger but I'll save that for later.
Don't have time today to go out to the highway and try it at 60 in 4th. But if the vacuum and the rpm are the same, the load should be the same (I hope).
AFR gauge wanders less too.

But the flat spot off-idle is a little worse now - guess I misdiagnosed the symptoms and there was significantly more contribution from the mains even below 2000 rpm than I thought. I may need to richen the idle just a bit (it's on the lean edge right now) and that's quicker and easier than pulling the bowls yet again.
Also I haven't even looked at the pump cam yet (.035 squirters, pink cam). Anyway it's not bad and I can live with it.

I also need to get out on the highway and make sure I'm not too rich at higher rpm's on the primaries.
Then I can try (very) brief blasts on the secondaries (currently .030 SMAB, #86 SMJ).

Keep at it Dude, the more you do the more you learn

Lower the float levels and turn the mixture screws in maybe a 1/4 turn but one at a time......

Thanks, will try that on the next tuning session.

How much lower? It has "HP" float bowls with the large sight windows, and it's about 1/3 up the glass at idle. Fuel pressure 5 psi.

I can't turn the screws in any more, it's about as lean as I can idle it now... That's why I put a little more on the secondaries (2 turns) than the primary (1-1/2).

Could I go one size smaller on the mains (to #72)?

Sorry, didn't see your question.
I don't know exactly, it's a "hybrid" (QFT/Proform 950 body with 1.42" venturis, QFT baseplate with 1-3/4" butterflies, billet metering blocks, Holley Ultra HP fuel bowls).

The key seems to be a small enough IFR and a very small MAB (hsb). I have 16 cranking 27 initial 36 total, plus a vacuum advance hooked up to manifold vacuum (these blocks and baseplate don't have vacuum nipples at all). But 8" Hg at idle is not enough to provide any advance there. It could use more at idle (1200 rpm).

I'd ditch the vacuum advance myself cos like vacuum secondary carbs, they don't belong on a performance engine imo ever......

A performance engine that also does street duty can benefit though At WOT there's no advance anyway...

So, since last post I leaned the PMJ slightly, reduced the PMAB a hair, and also lowered the floats in both bowls 3 flats (half a turn on the nut).
Finally got a chance to take it out for a run this afternoon. I warmed it up enough to idle while trying to determine the exact source of a right front corner oil leak, drove 15 min to town (2 mi slow back roads/6 mi 60+ mph), filled back up on oxygen-free premium, idled through the automatic car wash and 15 min back home).

Current tune pri/sec:
------------------------
IFR .028/.028
IAB .078/.079
TSR .074/.074
MAB .026/.030
MJ 72/86
PV 9.5"
PVCR .059

I'm getting close. Low speed cruise (below 2000) is around 15-16. 60 mph (15"Hg.) is 14-14.5, not too bad. 50-60 mph gentle acceleration (10") doesn't change much. Brisk acceleration (5") with PV open, about 13. With the primaries open at the secondary linkage start, it's in the high 12's. Looks like one more jet size to #71 might do it!

I tried one brief blast with all four barrels open from 3000 to 4200 rpm (man, did it get there quick even in 4th!) and managed to catch a peek at the AFR dropping below 12. So the #86 secondaries are too rich, not a huge surprise since I'd expect a .059 PVCR to provide about 10-11 jet sizes worth from #72. Will drop them 2 sizes on next test.

The only remaining problem (at least until I have the nerve to run it up to 6000+) is the lean flat spot during transition. I don't have enough experience to know if it's late mains, early end of t-slot fuel, and don't want to cover it up with squirt until I've tried my best to tune it out. Frankly it doesn't bother me, I'll just push a little harder on the loud pedal and get past it!

Nice!!!!!!!