Engine dies when warm

[egonz]

Hey guys newbie here trying to get my slant 6 going in my 73 duster. It turns on fine and idles beautifully. After it warms up and the choke opens it also will idle nice. When I go to put it in gear and let off the brake it creeps forward on its own well but the second I step on the gas it will die out & then won’t restart unless I keep my foot on the gas but as soon as I let off it will die again. Any idea what would be causing this?
Here is some information:
Holley 1945 reman, i have one that ran previously on the car about a year ago and one I got a few days ago from classic industries - the problem happens with both.
Valves have been adjusted .010int .020ex
cylinder pressure is around 110 on all cylinders except #1, it is about 95
New plugs, wires, & distributor
Vacuum is 19-20 Hg at idle

 

[Inertia]

Did this problem exist before you adjusted the valves ?

 

[egonz]

Yes it did. I adjusted the valves because one of the cylinders was missing, intake valve on #5 had no lash and was being held open

 

[Inertia]

Thanks.
At the start of my apprenticeship, although I had adjusted plenty of valves, the first coupla slants didn't turn out well.
My mentor told me to do 11 and 20 from then on.
I did notice the difference, so did the vehicle owners.
trivia .

 

[egonz]

Thanks.
At the start of my apprenticeship, although I had adjusted plenty of valves, the first coupla slants didn't turn out well.
My mentor told me to do 11 and 20 from then on.
I did notice the difference, so did the vehicle owners.
trivia .

Sounds like a it’s worth a shot, thanks!

 

[Dana67Dart]

Sound a bit like a vacuume leak or no vac advance.

Vacuume leak because when choked it runs fine
Choke adds fuel to a vacuume leak engine.

No vacuume advance or vacuume advance on the wrong port.

If no vac advance, giving gas will tend to cause the engine to die

Vacuume advance on the wrong port and it might retard the timing when the throttle is cracked open. (If set up for ported vacuume there should be none at idle, if it was attached to manifold vacuume, high at idle, and the timing was set with the vac advance hooked up. When you open the throttle the advance would be reduced due to lower vacuume signal .

 

[egonz]

Sound a bit like a vacuume leak or no vac advance.

Vacuume leak because when choked it runs fine
Choke adds fuel to a vacuume leak engine.

No vacuume advance or vacuume advance on the wrong port.

If no vac advance, giving gas will tend to cause the engine to die

Vacuume advance on the wrong port and it might retard the timing when the throttle is cracked open. (If set up for ported vacuume there should be none at idle, if it was attached to manifold vacuume, high at idle, and the timing was set with the vac advance hooked up. When you open the throttle the advance would be reduced due to lower vacuume signal .

Thanks for letting me know, I have the distributor hooked up to ported vacuum. But I will look around for a vacuum leak.

 

[Dana67Dart]

Thanks for letting me know, I have the distributor hooked up to ported vacuum. But I will look around for a vacuum leak

Did you set the timing with the vacuum advance disconnected and capped off?

 

[pishta]

in gear and it dies sounds lean. Choked richens the mix (higher vacuum from the choke restrictions) and off idle its back to lean. Unscrew the mixture screw 1/2 turn and see if there is any difference. If not turn it back, its free. Another Gotcha is the fuel filter: if its horizontal, it can generate an air pocket at its highest point that will prevent the bowl from filling when it gets warm, leaning out the carb (again, lean). Both free to check. If it happens on both carbs, its probably not the carb. but check your accelerator pump shot to be sure its not something easy.

 

[egonz]

Did you set the timing with the vacuum advance disconnected and capped off?

Sorry for the late response but I havnt been able to work on my car until today. I sprayed carb cleaner around the manifold and brake booster and did not notice a difference in rpm, is there a better way to find a possible vacuum leak?

Also I tried connecting the vacuum advance to manifold vacuum and the problem still occurs.

I did not set the timing with a light because the tab on the timing cover has broken off. I found TDC and got it as close as I can. While the car is in park I can mess with the throttle and bring it up to any rpm without a problem. Wouldn’t incorrect timing cause it to die when I do this no matter what gear it’s in? Like I said I’m still new to all this.

 

[egonz]

in gear and it dies sounds lean. Choked richens the mix (higher vacuum from the choke restrictions) and off idle its back to lean. Unscrew the mixture screw 1/2 turn and see if there is any difference. If not turn it back, it’s free. Another Gotcha is the fuel filter: if its horizontal, it can generate an air pocket at its highest point that will prevent the bowl from filling when it gets warm, leaning out the carb (again, lean). Both free to check. If it happens on both carbs, it’s probably not the carb. but check your accelerator pump shot to be sure it’s not something easy.

Sorry about the late response, I tried adjusting the idle mixture screw and no difference. Accelerator pump is working on both carbs. the fuel filter is almost horizontal and there is a small bubble along the top of it. I will see if I can move it to a different location and see if it helps.

 

[Dana67Dart]

I did not set the timing with a light because the tab on the timing cover has broken off. I found TDC and got it as close as I can. While the car is in park I can mess with the throttle and bring it up to any rpm without a problem. Wouldn’t incorrect timing cause it to die when I do this no matter what gear it’s in?

You are going to have to fix that.

Alternately you can accurately find TDC and make a new mark on the balancer or front cover.

As for not happening without a load.
If the timing is anywhere close it will run without a load but load up the engine and then the timing needs to be correct.

Have you checked to see if the vacuum advance is working? When you hooked it up to manifold vacuume the advance should have gone up and the rpm should have gone up significantly

 

[pishta]

Is the choke all the way off? Id let that thing idle for about 15 minutes and then tap the gas to make sure the choke pulls off the high idle ramp. It should set choke to wide open and settle into a 600ish idle. IF the choke never opens, hitting the gas will cause is to sputter and die. I had a Honda that had a manual choke and I'd know immediately that I forgot to push the choke off if it bogged hard on the gas.

 

[egonz]

You are going to have to fix that.

Alternately you can accurately find TDC and make a new mark on the balancer or front cover.

As for not happening without a load.
If the timing is anywhere close it will run without a load but load up the engine and then the timing needs to be correct.

Have you checked to see if the vacuum advance is working? When you hooked it up to manifold vacuume the advance should have gone up and the rpm should have gone up significantly

I think you’re on to something, rpm did not change whether it was ported or manifold vacuum. I ordered a timing light & am going to get it fixed this week.

 

[egonz]

Is the choke all the way off? Id let that thing idle for about 15 minutes and then tap the gas to make sure the choke pulls off the high idle ramp. It should set choke to wide open and settle into a 600ish idle. IF the choke never opens, hitting the gas will cause is to sputter and die. I had a Honda that had a manual choke and I'd know immediately that I forgot to push the choke off if it bogged hard on the gas.

It does come off the high idle ramp but doesn’t fully open. I’m going to bend the linkage a bit to get it open more

 

[pishta]

There you go!
See if the divorced choke (the heated spring under that dome cover) even moves when warming from cold with a heat gun or something. Sometimes they break. If it does make sure its at operating temp and turn adjuster screw on side of spring (if it has one) or bend the choke rod so it sees 90 degree choke butterfly at full operating temp.

 

[slantsixdan]

That '70-'72 choke thermostat's pushrod was meant to hook to a Holley 1920 or Carter BBS (final bend at the carb end of the choke pushrod is to make it point forward). The Holley 1945 carb on your engine requires a choke pushrod with its final/uppermost bend making it point rearward. Bends below that are configured to clear obstacles and allow the pushrod to move freely without binding. Someone has rigged up your setup to have a choke pushrod that would connect to the 1945 (top bend points rod rearward)—probably by robbing the pushrod from a '74-up choke thermostat. But that's a different kind of choke thermostat, and the pushrod length and angles are different. That's probably one of the reasons why you're now having difficulty. It's also probably why the cap is missing, which adapts the small choke pushrod to the large hole in the choke thermostat housing (required to allow the rod to move in accord with the arc of the carb's choke lever without binding down at the thermostat). This cap is there to trap heat so the choke won't re-close too soon and cost you gasoline money.

That '70-'72 setup, with the open-hole mount for the choke thermostat/cup/gasket, is prone to exhaust leakage and other nuisances.

In your shoes, I would fabricate a blockoff plate and gasket to go in place of the present choke cup, and perch a № 1234 electric choke kit atop the plate. End of all choke problems.