Hi all,
I was trying to follow the instructions from the dodgetravcos site and set timing 0n my 440 to 38 BTDC at 2600-2800 rpm.
I just cant get there.
I have a 440 with a Comp Cams 280H cam and a Street Demon carb (the newer Thermoquad/Quadrajet hybrid style)
When I turn the idle set screw all the way down I only get 2350 rpm.
Car seems to run fine, has good power.
What am I doing wrong? Is something limiting the idle mixture screw at idle in Park?
can I just set 38BTDC at 2350 RPM.
Any help or advice would be greatly appreciated.
Thanks
Vic

lets get started, what is the lowest good/stable hot idle speed you can get & what is the initial at that point? ported or manifold timed?

Are you trying to tune this motor for a car or motorhome? If for a car with stock distributor set the total mechanical timing at or above 4500 RPM in nuetral, make sure and disconnect the vacume advance hose to the distributor when setting the total timing. I like and use the initial timing to be set at or near 14 BTDC to 18 BTDC idling in nuetral below 1000 RPM That usually requires shortening up the mechanical advance slots in the distributor by welding them up and changing the length of them to be able to get 34 to 38 degrees total timing
IHTHs

Bear with me, I am learning.
I set the timing with the ported vacuum blocked. I need an idle speed of about 950-1000 rpm (18BTDC) in park to get 850 in Drive with the lights on. (otherwise it dies)

This engine is in my 1973 Charger.
Darn, was I was supposed to do this in neutral? Well i'll try again.
I know I look dumb here, but all my other old cars are manual transmissions so I had to know less to get them to run... I guess.
The dodgetravcos site was just a link I found.
Thank you
vic

we're all learning bro. the lowest hot idle speed in drive you can get is 850? Can you bump up the initial to where at the lowest idle speed you can get from doing that showes no/little vac from the ported port (some cans take more in hg than others to start)? You want no adv at idle and for the springs to start ~100-200 above the idle speed, using just the single stock light spring with one coil cut off might let the adv start ~1000 RPM. with the initial timing set you can then shorten the slots to get 36-38. FBO has the plate for $25 which is a quick & easy alternative to welding/filing the slots. Edit Yes set total in neutral (cuz it is high RPM so no need to have it up on blocks (in drive) & revved to the moon), initial timing set in drive as that is what the eng will see stoplight to stoplight so you want to replicate that in your driveway

I can get lower than 850 in Drive, but not with the lights on. This cam seems to be unhappy with any accessories or lights on. My builder put in it and I didn't think to ask about what it would do to daily drivability.

Tell me again about the vacuum, I have a vacuum gauge in the car and I use one to tune, but I always disconnect the ported vacuum. So I think you are saying I want to bump up the initial timing (at operating temp) until ported vacuum drops to zero. Is that right?

put the gauge on a manifold port & bump the initial up till you get the highest vac reading you can, all the while slowing the eng back to 850 in drive (or even a bit lower than 850 if possible) but not a deal breaker as it sounds like 850 in drive is as low as it can go for a good stable hot idle with the lights on, then retard the TIMING slowly till the VAC drops 1". at that point your initial you have that is your IDEAL initial that your eng with all its uniqueness/intracies wants/needs. 18-22 initial might be a good range but post what you get. at that point see how much vac the ported port has and plug in the can & see if the timing jumps. More later, I'm gonna hit the hay in a minute. the stock car might be finished/running tomorrow

got it, I'll post an update tomorrow. good night

Do any of you guys ever read what the original questions?
He is trying to get the curb idle screw to run the engine up to 2800 rpms.

To answer your question. Manually move the throttle by hand to the 2800 rpms. Then adjust the timing to where you want it.

Digger73 (Mike)

No we dont read the original Q's, we just wing it! (relax bro we'll get there). it was a slight bit ambiguous (at least to me) so I just started from scratch to see how it developed

Rapidrobert,
I just set it up as you suggested. 1" less than maximum vacuum gets me 16.7 BTDC initial timing on my digital light at 830-850 in drive

Nothing ambigious here! & no offense was meant by my (prior) comment, I was more complaining about the complainer. OK, plug in the can to ported & see if it gets activated (we're hoping not) and see what springs are in the dist (OE is (1) light one and (1) heavy one with an elongated loop on one end) & you'll need to bump the eng over or use a 1&1/4" socket on the big front bolt (if hand turning pulling the plugs sure helps. is this a BB? How would you like to shorten the slots (weld up/file down-a pain or the FBO plate-$25 to your door, it does work well & has 10-12-14-16-18 deg slots & is a drop in deal)

Initial timing hot at 850 in drive was 22BTDC making maximum manifold vacuum (14.5-15). When I retarded it to get a 1 " hg drop (13.5-14.5), I get 16.7 BTDC (sorry this was before your very last post) I'll check the can now

yes. it is a 1969 RB block. I looked at the FBO site and unless I'm reading it wrong, those plates are for an FBO distributor. Will they work in a stock distributor as well?

Yes, I just checked their site and their instructions are a bit ambiguous as their wording saying that the instructions are for FBO dists only might (easily) lead a person to conclude that the plate only works on their dists (& cost them sales as I'm sure you're not the only person that came to that conclusion). Actually it is good for ours & that one J685S is the one you need & the spring kit for $10 would likely be a timely purchase (not sure what tension they are but likely are in the ballpark & are for sure needed).

I checked timing with and without ported vacuum connected. There was no difference.
I turned the car off, took the distributor cap off and pulled vacuum with a Mitivac to see how the vacuum advance was set. The vacuum would start moving the floor at 12 hg and stop around 20ish. So although my advance didn't visibly change when I was running the car, the vacuum test tells me vacuum advance should have been starting to kick in since I idle around 12-15'hg

Thank you Robert. This will be my next mod!

Close Brando, ported vacuum doesn't provide vacuum at idle. It kicks in at part throttle. You're actually in good shape here.

yes there should not be any vac on that ported nipple (& we dont want to have to tune for manifold vac) but with the idle speed being a bit high I just wanted to confirm that we are still on ported.

Few do ... If his distributor is stock and never been recurved he is not going to be able to get his initial up to 16 plus degrees and not have his total mechanical below 45 ... Stock distributors usually have 30 degrees of mechanical advance built into them.


I'm not even sure he has said what distributor he has ??

Understood,
I wanted to make sure it wasn't active at idle.

I have a stock distributor, but I have no idea what the previous owners did to it in the past. I'm tearing into it now.

That's the first place to start , without that knowledge you , or anyone else , can't possibly know what to do .

Is it points or electronic ?

With some long thin needle nose pliers you can spread the clip enough so you can lift it out with out mangling it (might take (6) "spreading" attempts to get it wider than the nub tho I've spread it some then grabbed a vertical leg & ripped it around to the open side & up in one motion & reused em many times. OE would be a light spring and a heavy spring with an elongated loop on one end and the plate will have a number on it (underneath) for the amt of (dist) adv it has (the slot length(s). I would highly suggest ordering the FBO plate/springs which I believe you already have as it is a must have. We have the initial finalized & the plate will set the total then we can move on to the springs then on to the can. One caveat, the slot plate always want to come up off of the weight nubs which is a real pain if the (2) thin round base plates are in place so ANYTIME you are removing the reluctor up off the shaft ALWAYS press down on the top center shaft with your thumb on your free hand and when removing the rotor press on the reluctor underneath it. EDIT Yes I had ASSuMEd that it was electronic! MORE EDIT then we will address rotor tip clearance and Rotor Phasing (how could I forget that) and reduce lower shaft axial play to .005"

Most of the stock Mopar OEM distributors will have the amount of mechanical advance stamp (usually from 10 to 14 camshaft degrees(with a R or L after the numbers) which is twice as much degrees on the crankshaft ) onto the bottom of the advance plate. The advance plate is what the rotor rides on, to shorten or reduce the amount of mechanical advance you will need to shorten those slots equally. For instance if the number is 13 that means you have a maximum of 26 degrees crankshaft advance with that distributor, I measure the length of the slot and the diameter of the pins on the advance wieghts and subtract that from the slot length, the length of the remaining slot can be divided by the 26 for the amount to see how much each degree equals in thousands and shorten the slot up by the amount you want to have. For instance say the total slot length is .750 and the pin diameter is .250 so the remaining slot length is .500, divide 26 into .500 to get the amount in thousands each degree is, which on my calculator is .01923 rounded to the fourth place after the decimal point. So if I wanted to have 16 degrees mechanical advance I would shorten up the slot to be .30768 or rounded off at .307 So if you do that and set the initial timing at 16 degrees BTDC you would have 32 degrees total timing or if you set the initial at 18 BTDC you should have 34 degrees BTDC total timing. Hopefully you get the main thinking on this even though it is not dead nuts accurate on the actual measurements.

Robert,
OK I got the Plate-spring -book combo from FBO.
I am not sure where to start because there is no explanation given for the black, silver and gold spring. I know its change-and-test to get the right combo.(I have 2 MSD billets in my other cars so I get the overall concept)
In your experience, what plate/spring setting is a good starting point. Its only a street driven car, but unfortunately the cam drove me (through buy-try-buy-success) to a 2800 RPM stall converter.
thanks and very respectfully
vic

Vic (1) set the plate on the pair of rectangle slots that will give you 36 total (start with the 10 pair) then check total with can capped. (2) Keep the light OE spring in there & sub in the lightest one of the (3) FBO springs for a start & romp on it up thru the gears & if it pings then sub in the next heavier one & repeat. You want to be a bit under the pinging point on your hottest/driest day up thru the gears. slight pinging can be hard to hear sometimes and there is silent ping so just stay a bit under it as pinging is extremely damaging. (4) for a stable/repeatable idle you also want the springs/slots to not start advancing any lower than 100-200 RPM above your hot in drive idle speed which is what the eng will see at the stoplight (in other words so you ain't into the springs while idling. A friend has the "tuning to win" booklet & I was not impressed by it. it'd be good for a strickly 1/4 mile drag racer only imnho but I did glean a few good tidbits from it. We have the initial finalized & we're on the slots then the springs then we'll hook up the can & work with it

sounds like a good plan!

Robert,
Done!
10 on the plate and one light FBO spring. 16 initial.
took car out for a cruise and every thing seems nice and responsive.
But I do I get a backfire every time when I stomp on it hard enough to get the manifold vacuum to drop around 5"hg.
All of my carb diagnosis books that discuss backfire say to check choke plate binding or wires/plugs.
not sure if baking off vacuum advance will help ( retarded advance is usually associated with hesitation, but not backfiring in my books)
does this sound familiar? Any ideas?
Thank you
Vic.

you have 36 with the can capped? One backfire then it pulls hard (or not)?is that a backfire in the carb or out the tailpipe(s)? is the AP giving an immediate/healthy (quantity/duration) stream immediately on tip in (you jerk the throttle & it is squirting)?

Yes, with it capped (dependent on the accuracy of my digital timing light)
But I made this cruise with the vacuum advance connected
I'm pretty sure it is a tail pipe back fire, it sounds like its coming from the pass side. I didn't have the nerve to see if it pulls through the backfire(I didn't think it was recommended). but it did happen 3 separate times

I'll have to check he AP in the morning and report back

yeah we gotta get the backfire taken first. More info on that, at what RPM /amt of throttle (part or WOT) is it doing it/just once or multiple times

OK, AP squirter looks good.

The backfire events were a single POP at WOT (or close to it). I got it to happen 3 more times.
Each time I was cruising at 45-55 mph. When I stomped on the gas quickly the car would backfire. I would hear only one POP. I have a vacuum gage in the car, so I watched it after the first back fire. When I would rapidly stomp on the accelerator pedal the manifold vacuum dropped to 5 " Hg or below and the POP was heard. then I tried a deliberate but slower acceleration and I could get to 5 Hg without a POP. I didn't note the rpms, I'll have test it again to get to back on that.

disconnect the can & retry it & see if it still pops (rotor phasing issue). the floats are set correct & you said the squirt was pretty healthy? I'm trying to decipher if it is a lean condition (which it sure sounds like) to continue further. EDIT will it rev above 2350 RPM like it was stuck at originally?

I will re test without the vacuum advance can and report back.
yes, it gets above 2350, just not with the idle set screw, I needed to use the accelerator pedal.
Seems pretty dumb on my part, the idle screw isn't long enough to get beyond 2350, but I could have just used a helper at the gas pedal

Robert,
I haven't forgotten to get back to you. I has been raining here in Maryland almost every day since mid May, so its difficult to find a good time to test and tune. I will run it with out the can as soon as can ad let you know the results.
thanks
Vic

No rush bro

Did you set your idle mix screws to max vacuum? Take them all out 1/4 turn at a time for max vacuum then put back in 1/4 turn. Start all at 1.5 turns out. All should end up set at same number of turns out.. After setting timing do again. Correct Robert?
Stop turning out idle screws to raise idle..
Where are u in MD. Our weather sucks.

Robert.
I got a day without rain!
I drove it with vacuum advance disconnected and it still popped/backfired.
I will report what I noted, but its not very technical.
The pop only when I nailed it rapidly after about 10 min of diving. It happenedd on a level or slightly downhill grade and the engine was around 4000-4500 rpm(, by the time I looked down it was falling through 3500 rpm.
This is NOT the way I intend to treat this car on a daily basis, but I will have to get up therein RPMs to pass occasionally

so it seems as if the vacuum advance is not the culprit, but I'm not sure.
Whats my next move?
thanks
Vic

sounds like it's a lean backfire

Did you have the vacuum line plugged? I take it you took it loose from the distributor end.

by pulling/capping the can I wanted to elim Rotor Phasing as the culprit as RP has a special place in my heart (Please dont ask!). Nothing further is hitting me at the moment but the guys here will uncover it, just keep after it/be patient (pray for sunshine)

Yeah, it sounds like you learned a hard lesson the hard way.
So now I'm guessing lean fuel condition at high RPM I'm thinking fuel filter, fuel pump, fuel line before I look at jetting
Does that sound right or am I way off base?

Thanks see my question to All below

Yes, I was careful to plug it

if you're confident you have the timing the way you want it, now you can start trying to tune the carb.

first thing to look for is that you're getting a good pump shot as soon as there is any throttle movement. you can see this just by moving the throttle and looking for the shot, car doesn't even need to be running...

then you probably should set your idle speed, and then idle mix. then you can start making a single change at a time, after every change reset your idle speed and idle mix, then go test.

Hey Robert,
Ever since I but in the FBO plate I have been wondering why the plate does not bind on the counter-weight tabs and the top shaft. It seemed like a tight fit and I didn't add any grease or lubrication between the top shaft and the FBO plate.
It took a little effort to move it by hand, but I was too focused on getting it back together and in the car.
Was I supposed to lube the plate/top shaft contact area?
thanks
Vic

it would not hurt to just barely moisten the 1/4" nubs. yes the plate shifts a bit eccentric when the weights swing out. If you twist the rotor & let loose & it snaps back you are set on that Q. Now you will be going back inside to finalize the spring combo several times at least to get it dead on