I have a 1968 plymouth gtx. the car sat in a garage for twnety years. After some minor adjustments it fire right up and purrs like its brand new. I changed the carb to an edelbrock 750 cfm, new plug wires and so9me other tune ups.

when I stomp on it it stalls out. It feels like there tons of torque but it won't get up and go.

Any idea where to start.

Thanks

Evan

 

Put a vacuum guage on it and tell us what vacuum you are running 12-14 at idle is good. Could be timing and or carb also.

 

The vacuum is steady at 15. not bouncing at all

 

Evan -

A steady vac pressure doesn't totally preclude a vacuum leak.

Check the timing, s/b about 10 advanced initial to about 32 - 34 total.

Check for exhaust (or intake) obstructions.

Archer

 

Get it rolling first then hammer down on the accelerator and tell us what it does. Holley carbs have a shooter, pump and pump cam that are all adjustable with a tune up kit. I know nothing about Edelbrock carbs but they should be about the same. You could be starving it when stomping on the throttle.

 

What did it run like before you put the 750 on it? The factory carb was just a little spread bore, almost not noticeable, but that difference kept the air speed up and helped on bottom end, when you stomped it. It could be that the carb is just a tadd oversize when it comes to the bore balance and is killing the takeoff.

 

I tend to agree with Buck, the carb may be more than what the motor needs. But grab the ajustment kit with springs and jets,you get a graph on ajusting for better performance and driveability

 

An Edelbrock 750 isn't too much carb, the Thermoquad was 850 if I remember...you could put a 950 Holley on it, jet it and go if you were so inclined.
I would look for a problem in the accelerator circuit. Is fuel shooting out when you press the gas pedal? Maybe the shooter nozzle is too small? Is the jetting correct
Smoething is wrong with the set up of the carb...assuming it ran correctly 20 years ago.
I would also suggest taking it easy on a car that has sat that long.

It's also possible the advance in the distributor isn't working.

 

Edelbrock, whether AVS or AFB are essentially "demand controlled" because of the rear air door or flapper. 750 is not too much for a decent 440.

I agree with the others, look into the ignition curve and other standard "tune up" stuff. Is the exhaust plugged, the heat riser free, does it even HAVE a decent exhaust system, is the engine running "up to temperature," and is it getting enough fuel?

Not knowing the history, might even have a nylon cam drive that failed.

 

Not to overlook the obvious but fuel pressure and flow? If it runs great at lower rpm and transitions to part throttle nice but then plateaus when the throttle is opened up are you sure carb is getting fed?

 

Does it catch and run at all on wide open throttle? If it just lays down completely and only runs on part throttle it could be a main jet problem. Either too small or plugged up.

 

Thanks for all the suggestions. I will try a few of these this weekend and let you know the results.

I appreciate the help

Evan