Stalling on deceleration

[Fishfan]

Didn't know whether to post this under electric or engine. Could be either.

Here's the situation. I recently replaced water pump, intake manifold and carburetor (upgraded to 4 BBL) on my 66 Polara 318 Poly. When I got everything back together it wouldn't start. Turns out the Florida moisture and recent storms related to Hurricane Ian (which didn't hit us directly but did kick up a lot of weather in Miami) fried my MSD 8504 E-Curve distributor. I sent it to MSD and they repaired it. Installed it and car runs!

I did some initial fine tuning of idle circuit on the new Edelbrock 1406. Got the engine up to normal operating temperature and took her for a test drive. As engine got warmer, she got a little rougher. Then when decelerating/braking it stalled. Immediately started up again. But began stalling any time I would brake/decelerate from speed. At stop signs and red lights she was struggling to keep running. I'd put in neutral and rev her to keep her going. Would stall upon shift to drive unless I maintained some throttle. Got it home but was too dark to work on it. I did check the in-line fuel filter. It was clean and was full of fuel.

Today I tightened all the carb mounting nuts and started her up and checked for vacuum leaks around the carburetor by spraying carb cleaner around the mating surfaces (I have a Transdapt spacer) and didn't rev up to indicate a vacuum leak.

Any thoughts? I've read in other forums for other cars maybe the brake booster has something to do with it?

Float bowl height?

Why would operating temperature be implicated?

Timing? I marked the distributor before pulling it and put it back same way. But maybe too advanced? Not enough?

 

[5star1369]

You said you did some initial fine tuning of the idle mixtures. Is it manual, or electric choke? If the choke was still partly closed and you adjusted idle mixtures, when it gets fully open, the carb is too lean. Everything needs to be at full operating temps before fine tuning. I get needing to make adjustments to keep it running and let it warm up, but make sure you recheck it all once the motor is fully warmed up. Made the same mistake myself, on my first car, a 1975 Sport Fury with a 318

 

[cbarge]

Chevk your voltage going to your coil make dure its getting enough power under load.

 

[Davea Lux]

You can check the brake booster by unhooking the vacuum hose to it and plugging it off. If you then have a smooth idle, the brake booster is likely leaking internally. Usually you would also have a stiff brake pedal if this is the case. Do not drive the car with the hose unhooked.

Dave

 

[Fishfan]

You said you did some initial fine tuning of the idle mixtures. Is it manual, or electric choke? If the choke was still partly closed and you adjusted idle mixtures, when it gets fully open, the carb is too lean. Everything needs to be at full operating temps before fine tuning. I get needing to make adjustments to keep it running and let it warm up, but make sure you recheck it all once the motor is fully warmed up. Made the same mistake myself, on my first car, a 1975 Sport Fury with a 318

Electric choke. Was fully open when making adjustments.

 

['66 Fury I]

Check and set timing with a timing light. Relying on marking the distributor may not be as accurate as you hope. The timing light will also check the operation of your vacuum advance and stable ignition.
Checking for vacuum leaks with carb cleaner sounds messy! I've always used an unlit propane torch. Just saying! Lindsay

 

[Project Sketchy]

Unused vacuum fittings on the carb/manifold plugged? Ported or unported to vacuum advance?

 

[jimmyessbee]

You can check the brake booster by unhooking the vacuum hose to it and plugging it off. If you then have a smooth idle, the brake booster is likely leaking internally. Usually you would also have a stiff brake pedal if this is the case. Do not drive the car with the hose unhooked.

Dave

My 64 has the brake booster unhooked. I drive it that way. But I've got strong legs.

By the way... Anybody know where a guy can get a brake booster for a 1964 Chrysler?

 

[Davea Lux]

My 64 has the brake booster unhooked. I drive it that way. But I've got strong legs.

By the way... Anybody know where a guy can get a brake booster for a 1964 Chrysler?

It would be easier to have Booster Dewey rebuild it. www.boosterdeweyexchange.com. Nobody stocks these boosters anymore.

Dave

 

[jimmyessbee]

It would be easier to have Booster Dewey rebuild it. www.boosterdeweyexchange.com. Nobody stocks these boosters anymore.

Dave

I've heard that. Thanks. I've also wondered, though, on these older ones if a guy could just get rid of the booster. My assumption would be that it would take a different master cylinder. I've got to assume that the wheel cylinders are no different. Love to hear thoughts.

 

[57fury440]

I think it is a carb. issue. The carb. is new? Maybe it is running too lean. Try resetting the idle screws and make sure the electric choke is opening all the way.

 

[Davea Lux]

I've heard that. Thanks. I've also wondered, though, on these older ones if a guy could just get rid of the booster. My assumption would be that it would take a different master cylinder. I've got to assume that the wheel cylinders are no different. Love to hear thoughts.

Manual brakes were available, but you will need the smaller diameter master cylinder and a manual brake pedal assembly. It would stop better that way than with the current booster unhooked. The manual system has a different throw ratio on the pedal to make up for the lack of a booster.

Dave

 

[jimmyessbee]

Manual brakes were available, but you will need the smaller diameter master cylinder and a manual brake pedal assembly. It would stop better that way than with the current booster unhooked. The manual system has a different throw ratio on the pedal to make up for the lack of a booster.

Dave

I didn't think of the pedal. That might make it more of a struggle. I wonder if they would be similar for b-bodies of the age.

 

[Davea Lux]

I didn't think of the pedal. That might make it more of a struggle. I wonder if they would be similar for b-bodies of the age.

The short answer is no because usually the firewall is different.

Dave

 

[1971 300 Alvah]

Probably not your issue, but the silliest reason my car would die when I stopped... the spade terminal was not fully connected to the ballast resistor but was just sitting on top of it touching. When I started it and drove everything was fine, when I stepped on the brake momentum made the wire lift off of the spade and the car would die. The wire would return to it's spot resting on top of the spade and it looked normal and would start and drive again...

I found it while giving everything a jiggle...