cant seem to get it run right

[tim21391]

i know its a carb issue, but where to start.... i pulled a plug out and it had so much black soot on it.. so i know its running way to rich.. i took a wire brush and carb cleaner to each plug... but you have to take like 10 minutes of cranking to get it to start... and once you get it started it runs sorta ok.. i mean it still stumbles and such so im thinking power valve might be the problem but i dont know what size or whatever is the right one.. its a holley 750 double pumper carb on a 402.... then when u shut it off you have to take forever starting it again.... i doubt the floats are set right but i mean i pop the two access panel screws out and ive been told its right when u dont see any fuel coming out or at least a little bit.... its so un reliable because i never know if it will start or not.... i work at autozone so a guy i work with thought he might no the problem so i went to start it and had to take battery out to charge it since i had no cables so i took it to work to charge.. took it back and finally got it to fire.. then after i cleaned up plugs i had to put it back on charger because all the time cranking killed my battery...

[oldblue1968chevy]

Good luk, bump for ya

[Shyguy]

Is the 402 stock or modified? I only run a 600 cfm on my mostly stock 454 and it does real good.

A 750 double pumper maybe too much carb for the 402. Also one or both of the floats may be set at the wrong level or stuck.

See if you can borrow a carb off of a friend and see how that works.

I worked a "Zone" almost 4 years here in Southeast Missouri and then almost another year at a O'Rielly's. Got tired of the oil, grease and gasoline now I work as a maintenance person at a fabric store.

[mikey531]

Originally Posted by tim21391

i know its a carb issue, but where to start.... i pulled a plug out and it had so much black soot on it.. so i know its running way to rich.. i took a wire brush and carb cleaner to each plug... but you have to take like 10 minutes of cranking to get it to start... and once you get it started it runs sorta ok.. i mean it still stumbles and such so im thinking power valve might be the problem but i dont know what size or whatever is the right one.. its a holley 750 double pumper carb on a 402.... then when u shut it off you have to take forever starting it again.... i doubt the floats are set right but i mean i pop the two access panel screws out and ive been told its right when u dont see any fuel coming out or at least a little bit.... its so un reliable because i never know if it will start or not.... i work at autozone so a guy i work with thought he might no the problem so i went to start it and had to take battery out to charge it since i had no cables so i took it to work to charge.. took it back and finally got it to fire.. then after i cleaned up plugs i had to put it back on charger because all the time cranking killed my battery...

Did you buy the carb new? If not what was it used for before? Did you check to see what size the jets are? Are you running an electric fuel pump? Will it idle for ten or 15 minutes? If you get it idling look in the carb and see if gas is dripping out the squirters. I agree with what Shyguy said borrow one see how it reacts. Make sure you have good sparkplugs when you try a different carb.

[cdowns]

the type of manifold has a big effect on how engine will run too//trying a known good carb is a great first step

cam specs are another source of poor running conditions

[tim21391]

i gotcha. the carb runs well when its tuned right.. the engine was built back in 05 i just dont wanna rob the carb off my 347 stroker cuz it has different kinds of plumbing but i can prolly snag it and deal with it just have different lines and such

[webfoot]

If its stock it should have a 6.5 power valve. Knowing the primary jet size would be helpful too.

Lots of things could be afoul, what is the timing set at? Vac advance hooked up, to ported or manifold vacuum? Cam?