C2 Stalling Issue

[Dave N.]

I just rebuilt the carb on my 1965 327/365HP Vette and the car occasionally stalls upon braking. The car idles fine, accelerates fine and seems to be good to go however, upon braking the RPM's drop and the car stalls. The car starts right up after it stalls. If I feather the gas while braking I can keep the car running. Have checked electrical, etc. and am at a loss as to what happened. Had a C2 carb expert go through the cab and he can't find anything. Anyone see this before or have any ideas of what may be causing the car to stall? Thanks

[Michael W.]

Re: C2 Stalling Issue

Power brakes? If so, vacuum leak in the booster.

[Mike T.]

Re: C2 Stalling Issue

Dave - Power brake booster is something worth checking. Do you notice, when idling, any major change in rpm when you hit the brakes. Also, any idea if the float level was changed from where it used to be? Meaning, you and the guy you had check it out might have it right where the specs call for it but curious if it might have been a bit lower before the rebuild.

[Dave N.]

Re: C2 Stalling Issue

Power brakes? If so, vacuum leak in the booster.

No power brakes

[Timothy B.]

Re: C2 Stalling Issue

Dave,

Gotta try the simple things first, lower the primary and secondary float levels three flats on the adjusting nut, turn the assembly clockwise to lower.

If it has the brass lock nut loosen it and with a screwdriver turn the assembly clockwise 3/4 turn. Only do one thing at a time so you can go back if it does not correct the problem.

[Joe C.]

Re: C2 Stalling Issue

Chronic problem with Holleys and you'll never completely eliminate the condition although you should alleviate it by following Tim's advice.

[Ken A.]

Re: C2 Stalling Issue

Chronic problem with Holleys and you'll never completely eliminate the condition although you should alleviate it by following Tim's advice.

It can be eliminated by richening up the idle circuit 2 steps (use a 60-80 drill set) & then you will able to adjust idle to a much lower rpm.

[Frank D.]

Re: C2 Stalling Issue

Lower the floats ?
For what appears to be a fuel starvation issue ?
I'm no Holley guy but that sure seems counter-intuitive to me...

[Duke W.]

Re: C2 Stalling Issue

I just rebuilt the carb on my 1965 327/365HP Vette and the car occasionally stalls upon braking.

It could be your driving technique. When a light turn red in front of you, do you push in the clutch and step on the brake.

It's better to lift off and not push in the clutch until the engine is down to near idle speed.

It's even better to double-clutch downshift as the car slows.

I had a similar problem with my erstwhile 1984 MBZ 190E 2.3. If I had to rapidly stop, like a light turning, and I wasn't close enough to reach the limit line by the time it turned red the engine would often stall eventhough I used the heel-and-toe technique to double clutch downshift.
I complained to Mercedes because it was clearly a safety issue, but they said there was nothing they could do. Nowadays it would be a recall!

I finally learned to not push in the clutch until the engine was literally dragging against the brake at less than 1000 revs. I sold the 2.3 in favor of a new '88 2.6, and the 2.6 did not exhibit the same problem.

Both engines have the Bosch CIS-E fuel system, and I think the problem was the way the deceleration fuel shutoff was set up. On the 2.3 fuel was shutoff virtually the instant you lifted off and did not resume until below 1000 revs. On the 2.6 there's about a one second fuel shutoff delay and fuel flow returns at 1200. Both engines idle at 700 in neutral.

I recommend no lower than 900 idle speed on a 365 HP engine if you want to avoid idle issues, and check that it has a properly functioning 236 16 or B28 VAC that is connected to full manifold vacuum.

[Timothy B.]

Re: C2 Stalling Issue

If the floats are high the fuel could spill over into the venturi tube and cause a rich mixture when the car stops. That's where I would start first, easy to go back.

Ken Anderson may also be correct but no way I am going to recommend getting out a .033 drill bit and enlarge the idle feed restriction. The stock IFR should be .031 and I believe the idle air bleed is .070 but unless you are familiar with these circuits they are best left alone.

IMO, another thing to check is the primary throttle blade position at idle. It's best when there is just the sight of the transfer slot showing (.010) and the idle is set with the secondary throttle blade stop screw. Then the fuel for idle is from the curb idle ports (screws on the side) and the transfer slots don't feed at idle.

[Ken A.]

Re: C2 Stalling Issue

If the floats are high the fuel could spill over into the venturi tube and cause a rich mixture when the car stops. That's where I would start first, easy to go back.

Ken Anderson may also be correct but no way I am going to recommend getting out a .033 drill bit and enlarge the idle feed restriction. The stock IFR should be .031 and I believe the idle air bleed is .070 but unless you are familiar with these circuits they are best left alone.

IMO, another thing to check is the primary throttle blade position at idle. It's best when there is just the sight of the transfer slot showing (.010) and the idle is set with the secondary throttle blade stop screw. Then the fuel for idle is from the curb idle ports (screws on the side) and the transfer slots don't feed at idle.

By enlarging the IFR it allows the throttle blade position to be reduced and covers the transfer slot allowing for correct idle as was intended in the original design. Do not mess with the air bleeds.

[Duke W.]

Re: C2 Stalling Issue

Don't you guys think it's a little premature to recommend drilling out idle passages based on a vague, nine word description of the problem ("upon braking the RPM's [sic] drop and the car stalls") before doing some basic checks like float level, proper idle speed/mixture, and the spark advance map?

I'd like to hear more specifics on the conditions surrounding the problem (Light braking? Hard braking?) along with answers to the driving technique issues I brought up in post #9.

I don't think this is a common problem on these engines. It was stated the carburetor was recently rebuilt. If the problem did not occur prior to the rebuild could the problem have been introduced by an error in the rebuilding process?

Duke

[Jim D.]

Re: C2 Stalling Issue

I don't think this is a common problem on these engines. It was stated the carburetor was recently rebuilt. If the problem did not occur prior to the rebuild could the problem have been introduced by an error in the rebuilding process?
Duke

Yup. Like having the float level too high like was posted above.

[Dave N.]

Re: C2 Stalling Issue

I just rebuilt the carb on my 1965 327/365HP Vette and the car occasionally stalls upon braking. The car idles fine, accelerates fine and seems to be good to go however, upon braking the RPM's drop and the car stalls. The car starts right up after it stalls. If I feather the gas while braking I can keep the car running. Have checked electrical, etc. and am at a loss as to what happened. Had a C2 carb expert go through the cab and he can't find anything. Anyone see this before or have any ideas of what may be causing the car to stall? Thanks

I think we solved the stalling issue. There is a plastic anti-sloshing guide that goes in the rear bowl that was left out on rebuild. Apparently some of the carb prints for 1965 show this component and some don't. The rebuild kit I had omitted this item. Corvette shop I spoke to said some have this and some don't plastic part. It appears there was a spec change on this carb at some point and certain versions of the 65 carb don't need this, others do.

Thanks to everyone that replied to this post

[Ken A.]

Re: C2 Stalling Issue

Don't you guys think it's a little premature to recommend drilling out idle passages based on a vague, nine word description of the problem ("upon braking the RPM's [sic] drop and the car stalls") before doing some basic checks like float level, proper idle speed/mixture, and the spark advance map?

I'd like to hear more specifics on the conditions surrounding the problem (Light braking? Hard braking?) along with answers to the driving technique issues I brought up in post #9.

I don't think this is a common problem on these engines. It was stated the carburetor was recently rebuilt. If the problem did not occur prior to the rebuild could the problem have been introduced by an error in the rebuilding process?

Duke

I think you're referring to me & if you reread my posts you'll see I was responding to other posters, not the OP. who very well may have other issues. If you have any technical expertise with Holley carburetors on Corvettes, you'll see the logic of my posts.