Yanking hard at idle???

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DSMRossi

DSMRossi

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Just finished my build. Moderately built 360, 10.5:1 or so compression and .475/.494 cam.

I bought what Torco advertised as a 2200-2500 stall converter.

When the car is idling and I put it in drive, it bogs down and dies. I’ve had to increase my idle speed to 1300ish to keep the car alive once I put it in gear. Once in gear, it drops to around 700ish.

I contacted Torco because to me it seems like the stall is flashing low, they said to check the tranny line pressure. Timing is at 34 degrees all in
 
I have to pretty much stand on the brake to keep the car from pulling forward in gear
 
That's what I figured, but I read Torco built good converters from a number of forums.
 
I would start checking for a vacuum leak. Not on the idle circuit, sucking air somewhere. Just trying to help, good luck.
 
I can see a vacuum leak causing a motor to stall under load, but that still shouldn’t cause me to have to stand on the brake, no?

The car is pulling hard. A high stall should allow more slippage at idle I would think.
 
YOu don't need more slippage. My 3500 convertor will push through the brakes at 1300RPM and you can feel it bump into gear. There is no reason that engine needs to idle that high.

What is your base timing? I know you said your total was 34 degrees, which is in the ball park but what is the initial/base timing set at?
 
I’d have to check. I normally set total as aggressive as I can without knocking and let initial fall where it may
 
DSMRossi said:
I’d have to check. I normally set total as aggressive as I can without knocking and let initial fall where it may
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That is a terrible way of tuning and may very well be the culprit of your issue. Initial is critical. depending on how much advance is in your distributer you may have very little timing at idle.
 
DSMRossi said:
Works perfect in the manual world lol
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The manual world is just more forgiving because you can idle an engine high as hell and/or rev it up to take off. The engine still may be tuned and running poorly.
 
Welp you hit the nail on the head. I was able to coax my idle down and sure enough it goes into gear without me having to have the brake mashed to the floor.

I have it at a hair over 20 degrees initial, that sounds crazy high no?

I’m going to have to play with my dizzy now to make sure it doesn’t shoot to the moon at wot
 
DSMRossi said:
Welp you hit the nail on the head. I was able to coax my idle down and sure enough it goes into gear without me having to have the brake mashed to the floor.

I have it at a hair over 20 degrees initial, that sounds crazy high no?

I’m going to have to play with my dizzy now to make sure it doesn’t shoot to the moon at wot
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Not crazy at all. I run 17/35 all in at 3500 on mine. I've run as high as 24 degrees initial with 34 total. If you have trouble with the starter you can run a start retard and pull 20 degrees out of it for start up.
 
It’s a little stiff, but still turning over. May take another degree or two out. But it’s working way better and flashing up to 2200 when on the brakes. Thanks!!!
 
DSMRossi said:
It’s a little stiff, but still turning over. May take another degree or two out. But it’s working way better and flashing up to 2200 when on the brakes. Thanks!!!
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That flash stall is stock, maybe lower. You definitely need a higher stall. I'd guess you'd be happy with about a 3500 stall but I'd call and give them your combo. If you had a dyno run logged it would help. But they can get you close without it
 
So what I’m finding is it wants to be right at 22 degrees at idle with the vac advance plugged.

Once I hook up the vacuum advance, revs start bouncing. In order to make them stable, I have to retard the timing to flatten it out.
 
DSMRossi said:
So what I’m finding is it wants to be right at 22 degrees at idle with the vac advance plugged.
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With that compression and cam my guess is the engine will be happy with less than 22* with a richer idle mix. If will also make more power at idle - so less drop in rpm when placed into gear. Just go a little at a time. Open up the idle mix screws a bit, then lower timing a couple degrees. Bigger timing leads are needed when the burns are slow. They're slow with lower compression, slow with lots of exhaust dilution, slower with lean mixtures. You may end up with an engine happy (in gear) with timing in the 16-20* range if you keep fiddling with it.
When the engine is cold - and no choke or fast idle - you may have to two foot it for a bit, especially in the winter.
Once I hook up the vacuum advance, revs start bouncing. In order to make them stable, I have to retard the timing to flatten it out.
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Does your carb have a timed vacuum port? When you are ready to hook up vacuum advance, use that. If it (timed vacuum port) is seeing vacuum at idle, the throttles blades are too far open at idle.
 
Mattax said:
With that compression and cam my guess is the engine will be happy with less than 22* with a richer idle mix. If will also make more power at idle - so less drop in rpm when placed into gear. Just go a little at a time. Open up the idle mix screws a bit, then lower timing a couple degrees. Bigger timing leads are needed when the burns are slow. They're slow with lower compression, slow with lots of exhaust dilution, slower with lean mixtures. You may end up with an engine happy (in gear) with timing in the 16-20* range if you keep fiddling with it.
When the engine is cold - and no choke or fast idle - you may have to two foot it for a bit, especially in the winter.

Does your carb have a timed vacuum port? When you are ready to hook up vacuum advance, use that. If it (timed vacuum port) is seeing vacuum at idle, the throttles blades are too far open at idle.
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It does - I've been using the manifold vacuum source for a couple years now.

I'll tray and bump it down to 18 degrees on ported vacuum and see if I can get it running good by playing with the mix screws.
 
Its worth a try. I struggled with idle in a similar manner until around '08 not really knowing what or why the timing at idle ought to be. I was using Turbo Action with (3000 stall) first with a CC 280H cam. Then had a Hughes cam with similar duration (223/230 at .050) and had Turbo Action tighten the stall as looking for better throttle response. Both ended up with Rhoades lifters which helped a little but weren't the magic bullet. Changing the stall in the converter seemed to effect part throttle moderate load and of course what it would flash to. Turbo Action said it shouldn't really effect load in idle. Is this accurate? I don't know enough about how stall is changed to assess.

On a practical level, 22* at 1300 may be 18* at 900 rpm. Depends how fast the begining of the timing curve is. It should idle under 1000 rpm. I've got mine down to around 780 - 800 rpm in N when warmed up. Its so much nicer deal with.
 
You could just run it without the vacuum advance. I always run straight time or mech only distributers anyhow.
 
Just curious, what are the rest of your cam specs? Duration and lobe separation play a bigger part than lift as far as idle smoothness.
 
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roccodart440 said:
You could just run it without the vacuum advance. I always run straight time or mech only distributers anyhow.
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Or at least get it running nicely without the vacuum advance.
If the advance curve isn't too fast, then adding the vac advance using the ported will improve the off-idle, part throttle.
If the advance curve is too quick or too much, then it will need to be slowed early or the vac advance will cause part throttle pinging on long trips and similar head scratchers. Been there, done that. LOL now....its how I came to dislike the Mallory built Mopar Performance distributors.

If the advance curve is way too long, like using an emissions era distributor with a hot rod, sometimes the vac advance can be used with manifold vacuum for the right timing at idle. As I learned the hard way, using vacuum advance to get the timing at idle is tricky and its not very stable.

Below is the advance curve for a sb Chrysler built Mopar performance distributor. Pretty decent curve for what we're talking about here IMO. This curve will work well with vac advance.
If the timing is set at 1300 rpm, then with the one I measured (gray line), it will be 3* less at 900 rpm and under.
Its worth noting if the timing was set to 35* at 2800, per MP recomended starting point, the initial will be around 17*. Pretty close for my setuup, maybe a little low for the OPs.
But say it runs best with 32* at 2800 rpm which gets 35* above 3500 rpm. That results in 14* initial. Easy starting but not quite enough for good idling with a combination that doesn't produce particularly strong vacuum at idle.
Point here is establish good timing for idle, and then best timing for WOT, after knowing both some tweaking of the advance curve may be needed. Vacuum advance can then be tuned in (if the centrifical curve isn't too fast)

P3690430-advance.jpg
 
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