Stalling
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Instructor
Joined: Apr 2004
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From: HOMOSASSA FL
Stalling
Gentlemen, 1969 350/300hp auto. 55,000 original miles is stalling only when put in gear. Items done and checked: High idle chock 1100rpm and 22 vacuum, normal idle 800rpm and 15 to 18 vacuum, has a cam, size unknown, timing is set at 3 to 4 btdc, carb idle air 2.75 turns out, vacuum leaks found none, isolated the vacuum from engine to body accessories by disconnecting the vacuum lines one at a time from the intake manifold tree to see if there were any vacuum leaks ie head lights, wiper door, heater controls etc, vacuum stayed around 15 to 18, does not smoke or smell of fuel or transmission fluid. The vehicle was restored 8 years ago and has 9,000 mile on it sense restoration. The vehicle can be driven and runs great if you feather the accelerator when you put it in gear, but when you come to a stop it wants to stall. Any thoughts ??? Ps I THINK I'M LOOSING IT. Steve
Racer
Joined: Oct 2001
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From: Portage La Prairie Manitoba
Is it an auto trans? Have you got power brakes?
Chock your wheels and start engine in neutral.... shift into drive without touching your brake pedal.
If it stalls... I would assume your torque convertor is locked up
If it doesnt stall then push in your brake pedal and see if that stalls it
Chock your wheels and start engine in neutral.... shift into drive without touching your brake pedal.
If it stalls... I would assume your torque convertor is locked up
If it doesnt stall then push in your brake pedal and see if that stalls it
Last edited by Engage; Dec 6, 2021 at 02:39 PM.
Thread Starter
Instructor
Joined: Apr 2004
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From: HOMOSASSA FL
Engage, It is an auto transmission and power brakes. I will try that process tomorrow and let you know.. The Corvette did move without stalling this morning. It was at high idle cold when the choke was on. As soon as it warmed up and went to normal idle, we put it in gear again and it stalled.. A little more added information..Steve
Le Mans Master
Joined: Apr 2011
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From: Hermosa
If nothing has been changed recently I'd check the vacuum advance can see if it's still working. 3* to 4* initial timing is very low, but if it was working before then I guess it's adequate to run.
you'll get solutions like make sure it's on manifold vacuum not ported and timing instructions for total 36* etc. Probably not bad advice, but if this is recent and not due to a change you made and you want to see what just stopped working then I'd check that vacuum advance to insure it's still functioning.
you'll get solutions like make sure it's on manifold vacuum not ported and timing instructions for total 36* etc. Probably not bad advice, but if this is recent and not due to a change you made and you want to see what just stopped working then I'd check that vacuum advance to insure it's still functioning.
Team Owner
Joined: Jan 2007
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From: Southern Cal Ca
St. Jude Donor '22
Gentlemen, 1969 350/300hp auto. 55,000 original miles is stalling only when put in gear. Items done and checked: High idle chock 1100rpm and 22 vacuum, normal idle 800rpm and 15 to 18 vacuum, has a cam, size unknown, timing is set at 3 to 4 btdc, carb idle air 2.75 turns out, vacuum leaks found none, isolated the vacuum from engine to body accessories by disconnecting the vacuum lines one at a time from the intake manifold tree to see if there were any vacuum leaks ie head lights, wiper door, heater controls etc, vacuum stayed around 15 to 18, does not smoke or smell of fuel or transmission fluid. The vehicle was restored 8 years ago and has 9,000 mile on it sense restoration. The vehicle can be driven and runs great if you feather the accelerator when you put it in gear, but when you come to a stop it wants to stall. Any thoughts ??? Ps I THINK I'M LOOSING IT. Steve
if the torque converter is good, I would add timing
Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
You need to add about 10-12 degrees of timing......checked with the vacuum advance unplugged. You want 36 degrees total at or around 3000 rpm. Record the initial but do not mind what the number is.....generally an HEI will be 15 degrees initial when set for 36 total. Now plug the vacuum advance in to a full manifold vacuum source and NOW you can set the idle screws.....but not until.
Jebby
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I was going to say the same thing, add some timing and start over with the idle set screws and go from there. If you have an aftermarket cam in it it wont want to run with so little timing and a stock on wants 5-6 for smog settings. Most of mine are at 14-15 degrees initial.
Look into getting Lars timing papers
Look into getting Lars timing papers
Thread Starter
Instructor
Joined: Apr 2004
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From: HOMOSASSA FL
REELAV8R, I agree that the timing is low. The people that own this Corvette had someone else work on the vehicle before me. They told me they brought it in for a tune up. That was six months ago. The Stalling problem started about a week after the tune up. I’m trying to figure out what he did. Long story...The vacuum advance is working. Check it with a timing light and a Mity vac to be sure.They are in the process to find the paper work on the motor that would tell me what the timing and other specification would be including cam specifications. Another part of the story is the garage that rebuilt the Corvette is out of business. I haven’t made any changes yet, just checks. Agree with the total timing procedure should be done. Thanks Steve
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Thread Starter
Instructor
Joined: Apr 2004
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From: HOMOSASSA FL
Rescue, I have Lar’s timing papers. When I restored my 1970 he rebuilt my carb. Great information Lar’s has. My 1970 is running around 14 degrees too. The cam is a big concern. I don’t want to reinvent the wheel. That is why I waiting for the owners to find the rebuild paper work. Tomorrow I’m going to do Engage’s procedure. Thanks Steve
Thread Starter
Instructor
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From: HOMOSASSA FL
Jebbysan, That is differently the timing procedures I’m going to do. Lar’s Style... I just giving the owner’s time to find the Rebuild Paper Work before I start tearing into their Corvette. The papers will help a lot.... One step at a time..Thanks Steve
Thread Starter
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From: HOMOSASSA FL
calwldlife, Those items are also on my list...Hope they will find the Rebuild Paper Work. This would make it easier on them and myself. I’m not as young as I used to be... Steve Ps It’s not the age, It’s the milage...Pss If you think or here of anything else please let me know...
Is my vette stock?? HAHA
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
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Rescue, I have Lar’s timing papers. When I restored my 1970 he rebuilt my carb. Great information Lar’s has. My 1970 is running around 14 degrees too. The cam is a big concern. I don’t want to reinvent the wheel. That is why I waiting for the owners to find the rebuild paper work. Tomorrow I’m going to do Engage’s procedure. Thanks Steve
Good luck, hope you get it sorted out. Curiious what the issue is
Thread Starter
Instructor
Joined: Apr 2004
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From: HOMOSASSA FL
Budryzer, At cold idle, 22 on the vacuum gage at 1100rpm’s The Corvette will move fine. Once warmed up 15 to 18 on the vacuum gage at 800rpm’s the Corvette stalls every time....I was hopping that someone on the Forum had seen this problem...I’m going to take the Corvette for a test drive this afternoon with the vacuum gage hooked up to the intake manifold. We will take the Corvette through a series of stops and starts etc. to see what is happening with the vacuum. Steve
Le Mans Master
Joined: Apr 2011
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From: Hermosa
I'm thinking when you put it into gear the RPM drops enough to drop the vacuum below the threshold for the vacuum can to fully actuate thus dropping all, or most of, the vacuum advance and leaving it with only initial advance which is too low really. The vacuum advance is probably the only thing keeping it running out of gear.
The carb is probably got the idle screw screwed in pretty far to get it to idle in the first place with only 4* of advance at idle. This is going to make the engine idle on the main jets and not the idle circuit as well. Rich smelling exhaust at idle?
The carb is probably got the idle screw screwed in pretty far to get it to idle in the first place with only 4* of advance at idle. This is going to make the engine idle on the main jets and not the idle circuit as well. Rich smelling exhaust at idle?
Last edited by REELAV8R; Dec 7, 2021 at 04:00 PM.
Team Owner
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From: Southern Cal Ca
St. Jude Donor '22
Gentlemen, 1969 350/300hp auto. 55,000 original miles is stalling only when put in gear. Items done and checked: High idle chock 1100rpm and 22 vacuum, normal idle 800rpm and 15 to 18 vacuum, has a cam, size unknown, timing is set at 3 to 4 btdc, carb idle air 2.75 turns out, vacuum leaks found none, isolated the vacuum from engine to body accessories by disconnecting the vacuum lines one at a time from the intake manifold tree to see if there were any vacuum leaks ie head lights, wiper door, heater controls etc, vacuum stayed around 15 to 18, does not smoke or smell of fuel or transmission fluid. The vehicle was restored 8 years ago and has 9,000 mile on it sense restoration. The vehicle can be driven and runs great if you feather the accelerator when you put it in gear, but when you come to a stop it wants to stall. Any thoughts ??? Ps I THINK I'M LOOSING IT. Steve
I don't have my vette repair manual for ALL years handy but I can imagine the 4 deg adv at idle with ported vac is spec.
Changing from ported to full vac will cause issues at idle.
The dist spring weights and vac applied early can cause issues with idle.
In other words if the car is totally stock and everything is connected in the stock way, the car should idle fine in or out of gear.
Problems happen when a system designed for
ported vac has full mani vac.
It goes like this, set timing to spec at idle and then add vac advance and car rpms go way up.
Set carb idle screw to offset the rpm increase and create a condition where the engine needs full vac to allow low idle screw setting to run car.
Le Mans Master
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From: Indiana
Budryzer, At cold idle, 22 on the vacuum gage at 1100rpm’s The Corvette will move fine. Once warmed up 15 to 18 on the vacuum gage at 800rpm’s the Corvette stalls every time....I was hopping that someone on the Forum had seen this problem...I’m going to take the Corvette for a test drive this afternoon with the vacuum gage hooked up to the intake manifold. We will take the Corvette through a series of stops and starts etc. to see what is happening with the vacuum. Steve