I have a 600cfm vac sec holley that i just swaped over from tpi. Im having a stalling after med load/accel then coming to a stop the engine almost dies smokes black and runs rough like its loading up. Ive rebuilt the carb after thinking somthing in there was causing it yet im still having same problem.

Floats are set i can get the idle mixture just about rite about (turned out 1 5/8s ea) i have to set the idle at about 900rpm or turning on the elec fans drags the motor down to much. (Another problem) Power valve is 7.5 jets are 68 engine is a stock 305 initial timing is set at 14*.

I dont know what else to do after i rebuilt it floats were set dry and got a real smooth idle after setting mixture secrews car even idled nice with fans on, then i went and touched the primary floats and it loaded up shaking and couldnt get it to idle smooth no matter what i did with float or mixture adjustment. So i changed the plugs, pulled the carb and reset the floats dry again.

And now after all that i started over and got the idle but same damn problem, after test driving it loads up and pretty much dies if i dont catch it and even then it idles like **** after until i restart it. But it doesnt do that under light throttle condition, im guessing its when the secondarys are opening or jets are to big???????

 

Check the fuel levels WET. Engine running at idle. Should be just below the level of the sight plug so some with dribble out if you bump thr fender hard.

Beyond that it sounds a little like a ruptured PV diaphragm or a weepy PV gasket to me. Had very similar symptoms on a 600 Holley once. It would idle OK steady-state but returning from heavy throttle it would load up and almost choke to death on fuel. Part throttle and above worked just fine always.

After checking everything else I replaced the PV gasket and instantly everything went back to sanity. Consistent idle speed and mixture, etc. The PV gasket had a small split in it and was leaking fuel, especially under high manifold vacuum conditions, like when lifting off the throttle at high RPMs.

 

The floats are right if i give the car a little bump the fuel will come out of the primary bowl and it needs a fairly hard push to come out of the secondary bowl.

I think you right on about the PV gasket when i removed the one the was in there it appeared to be double gasketed so i removed but i couldnt find the correct gasket in the rebuild kit. So i found the closet one and put it in with the 6.5 that was in there. Then after i took it apart the third time i tryed finding a gasket that would fit the 7.5 tho theres a difference in the 2. The 6.5 has 2 slot openings n the 7.5 has 3 holes but now i ended up putting the 7.5 in. Im going to get the correct gasket tommorow and see what happens!

 

Im guessing only difference between the 2 is the 6.5 is meant to flow more besides the vac rating.

 

Changed powervalve and gasket. Now after a short med throttle run after i get off the gas it dies then restart it wont idle and bogs like crazy, just as if engines running on 4 cyls or somthing... I dunno whats going on ive had 5 cars with 6 different carbed engines and never havent gotten the car to atleast drive normal. Im really lost now

 

First,you didn't say if you changed the fuel pump or not because that pump has way too much pressure for a carb. You could try a low pressure tbi pump in the tank or take it out and put a connector hose in the assembly and run a low pressure inline pump.

Second, you could try to run a bypass regulator and connect the bypass line to the original Tpi 5/16 return line.

Hope this helps.

 

Yea the pump was swaped outfor a low press carb pump but turns out pump was junk and couldnt keep the bowls filled got a nice holley blue pump and got it running rite.