Hello All--Ive been workin on my project 68 stang for a while now. Its 95% done, with the exception of some fine tuning, and minimal issues--which is why I am seeking some help.
The car has an 88 302 motor in it, with a Holley 750 Double Pumper (the carbis almost new and was free from my friend, so i couldnt pass it up). Its mounted on top of a torquer II intake manifold and I have flowtech shorty headers.
The fuel pump puts out 14psi, which i regulate down to 6.5. The battery is brand new and the alternator charges at 13.95 volts at idle with all electrical accessories on(fan, water pump, fuel pump---).
Heres my issue---Start the car up and let it warm up. It idles fine and everything. Ill go around the block, just cruisin, maybe 2500 rpms, and ill come back to the driveway and push the clutch in and the car will start to stumble/ idle rough and die (unless i throttle it a bit and keep the revs up). This ONLY happens after a drive, never before. Any Advice??? Im not sure where to start???? Thanks for any advice!!

 

Check your fuel filters. Idling uses very little gas, so a partialy clogged filter will not make the engine stumble at idle. If that isn't it, make sure the choke is opening all the way open when warm. If that isn't it, make sure you have a carb spacer under the carb so you don't experience vapor lock. It does sound like like a fuel delivery issue though.

 

There is no carb spacer on it. Im not 100% sure on vapor lock, just so I understand it correctly, vapors trapped under the butterflies are running it too rich to idle??

 

Perhaps a smaller CFM carb. and spacer should be installed?????

 

No, vapor lock is where the gas in the bowl of the carb boils, and only the vapor of the gas gets into the firing chamber instead of raw gas. Get yourself at least a 1/2" phenolic carb spacer under there. A 1" is best and will also help with throttle response.If you have an aftermarket intake and tall carb, you may have clearance issues from the hood to air cleaner. That is why the hotrodders go to a different hood like either a cowl induction or a shaker hood.

 

Soaring,
750 double pumper too much for that 302?????

 

ok--so i may even have a carb spacer around to test out---the vapor lock does make sense---would it only happen though after a short cruise around the block?? i mean i can start the car up and let it idle for literally half an hour without a single problem??

 

Vapor Lock is actually any point along the fuel system where there is enough heat and low enough pressure for the fuel to Vaporize..thus the term Vapor Lock.

It could be anywhere along the fuel system, not just the carb itself. The carb is just the most common point of vapor lock as it has heat directly radiated to it from the top of the engine. A spacer will help in curing the problem if that's where it's at.

Are you running an electric pump and mechanical or just electric?

 

A stock 302 should not have more than a 480 cfm carb on it.

 

Vapor lock is just one of several causes for your running rough after a jaunt around the block. Get the spacer on there, and if that doesn't cure it, then check the other things. The spacer will also improve your throttle response.