Hesitation at WOT

Hey guys,

I have been doing a bunch of R&R on my 1978 308GTB. I am experiencing an issue when going to wide-open throttle when the car will stall. The car will idle perfectly, and if I gradually open the throttle, I can run the motor up throughout the RPM range all the way to 7k without issue.

The trouble starts if I just hammer the throttle. The car will immediately stall out.

I assume this is an issue with the carbs, maybe the accelerator pumps or accelerator pump circuit? Is there anything else to try, short of a rebuild? Could there be anything in the ignition system that might be causing an issue?

Thanks for any pointers!

 

Easy enough to confirm/deny visually if the acc pump nozzles are squirting. Another thing to do is confirm the ignition is advancing as it should with a timing light. Is your ignition system still relatively stock (points and mechanical advance in each distributor), or has it been replaced with something aftermarket?

 

My '77 308 GTB, #22963, has done that for all the time I've owned it; since 10/18/88. When I was test driving it at FAF, I was told that this is a function of adding so much fuel, so quickly. I was made to understand that my heavy foot was the problem, that I needed to learn how to drive it, experience with it would solve the problem. I can't say that it's happened that way, I still can push too hard and make it stumble, but when I feed the carburetors "just right," the response is very satisfying.

It's 39 years old, It doesn't have computers that make it "easier to drive." It's not a self-driving carWhen "Power" is required by the steering, my forearms are the source. Without ABS, it is my foot that controls the intensity of the braking. I think all of us "car guys" should have a primitive vehicle in our stable, to remind us of how it feels to DRIVE, without all the help that modern automobiles give to modern, inattentive drivers.

Sorry Evan, but I believe that it's just part of driving a bona fide antique automobile.

Mike Flanagan

 

@Steve Magnusson I'm pretty sure I'm not getting the squirt from the ACC pump nozzles. I get a bit of a drizzle out of two of the eight, but the others look dry. I did disassemble and clean them as best I could today, but still just a dribble out of the nozzles.

Am I looking at a rebuild?

 

@MFlanagan this ain't right. It's a straight-up stall under WOT... like can't get up a hill stall.

 

Probably. You need to have the acc pumps working. You might take off one of the offending acc pump covers and have a look at the condition of the diaphragm. There are also various ball valves within the carb that can get stuck closed by varnish. Are you resurrecting your car from the dead (i.e., a long period of disuse)?

 

Sorry Evan, I jumped to a conclusion without getting all of your story. Please, pardon me.
Mike Flanagan

 

A classic symptom of accelerator pump malfunction. Could be in the pump assembly itself, the passages to the carb, etc.