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New to the forum. Came in search of everyone’s experience. Custom ordered an early 2020 C8 and love it so much I bought a 69 Coupe a couple months back at Mecum. Finally got around to “tuning” the carb and for the life of me, can not think of what I did wrong. The car starts perfectly (new battery) though it still idles high; like 1,200-1,500. So I have been adjusting the throttle stop screw and accelerator pump screw/bolt/nut to try to get her to idle around 750-800. However, I was going to take her for a quick test drive and now she’s stalling when I put her in gear. Either DRIVE or REVERSE, the RPM’s will drop immediately to 3-400 and then she’ll stall out.
Background: 1969 Coupe, originally had a 427, someone dropped in a 454. Has a 3 spd turbo automatic transmission.
Looking for any input/guidance on what I could have done to cause this? Or could it be possibly a whole new issue that just happened to start now? Thanks.
A '72 with 454 and auto should idle at 600 when in drive. The accelerator pump isn't used to set idle, so I think you need to return it to where it just begins to move with the first movement of the accelerator linkage. Then check to make sure the fast idle cam for the choke isn't engaged.
What carb is on the engine - (sounds like a Holley if you're adjusting pump)? Pics may help.
A '72 with 454 and auto should idle at 600 when in drive. The accelerator pump isn't used to set idle, so I think you need to return it to where it just begins to move with the first movement of the accelerator linkage. Then check to make sure the fast idle cam for the choke isn't engaged.
What carb is on the engine - (sounds like a Holley if you're adjusting pump)? Pics may help.
You guessed it. CARBURETOR: HOLLEY 600 CFM STREET WARRIOR CARBURETOR - Holley List #: 80457-13 - Date Code: 1560
Just a couple observations about your set-up in the photo:
Your throttle cable bracket has a 1/2" bolt / nut on the end. I think I would loosen that bolt and flip cable clamp 180* to the "up" position, snug it back down.
That will put the cable in a more horizontal position and less downward strain on everything.
I would also use that same bracket to hold a dual throttle spring (one inside the other) and have the springs ends hook into one of the three holes at the bottle of the throttle. Your current return spring is about to wear a dangerous hole in the fuel line.
Just my opinion but, that is not the ideal Holley model for GMs. Fuel inlet is on the driver's side. GM fuel pumps are on the passenger side.
All really sound advice… thank you! I am learning that the shop that sold it at Mecum appears to have cut a lot of corners. But I still love the car and I’m learning quickly and not afraid to try stuff. I’m in no hurry and ant to do things properly, though I am not concerned with “restoration”… just want to get it working right. :-)
Sounds like solid advice… thank you. I am learning as fast as I can, but having a blast working on this car. The clamp was really rather easy to flip. See below. I may look into a dual-throttle spring, though it has about 1/2-3/4” clearance from the fuel line. Not really visible from the angle I posted above.
Could there be an issue with the choke? I was reading another thread with similar issues.
Just a couple observations about your set-up in the photo:
Your throttle cable bracket has a 1/2" bolt / nut on the end. I think I would loosen that bolt and flip cable clamp 180* to the "up" position, snug it back down.
That will put the cable in a more horizontal position and less downward strain on everything.
I would also use that same bracket to hold a dual throttle spring (one inside the other) and have the springs ends hook into one of the three holes at the bottle of the throttle. Your current return spring is about to wear a dangerous hole in the fuel line.
Just my opinion but, that is not the ideal Holley model for GMs. Fuel inlet is on the driver's side. GM fuel pumps are on the passenger side.
I think it was the choke! Watched this video from Holley: https://www.holley.com/blog/post/how...y_carburetors/ and made some adjustments. Now I need to wait for the engine to cool so I can further adjust the fast idle screw. It’s been almost 30 years since I got this deep into a car and back then we didn’t have car forums and YouTube!
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Quick stall after put into gear
