Thread: still fouling plugs

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One of the carbs I tried was a rebuilt 750 holley double pumper in which I installed a 3.5 power valve.It still fouled the plugs thats why I dont think it is the power valve.Although this was an older carb without the power valve blowout protection and I could have hurt it without really knowing.
The pcv valve is hooked up to the back of the carb.And it takes awhile for the motor to start popping out the exhaust.The plugs will blacken pretty quick but not foul out right away.Ill get a true reading on the plugs with a full run and then shurt it off.I pulled a few of the plugs at the track after a run and driving back to my pit.They were not all the way back white but had cleaned up alot.The tip of the plug where you set the gap had some blueing on it like it was running lean on the big end.So maybe I can restrict the fuel a little at idle or put bigger air bleeds in to add more air at idle to stop fouling plugs,what do you think?This rich mixture at idle will cause a miss right?

what jets do you have in the 750 dp carb?
how much fuel pressure are you running?
How high are the floats set?
How much oil has it used?
does the carb/spacer/manifold have a good seal?

With the amount of compression that you are getting, I suspect the cylinder head package

Jerry

Originally Posted by jerry clayton

what jets do you have in the 750 dp carb?
how much fuel pressure are you running?
How high are the floats set?
How much oil has it used?
does the carb/spacer/manifold have a good seal?

With the amount of compression that you are getting, I suspect the cylinder head package

Jerry

I am running a new Quickfuel super street 750 mechanical secondary carb now.It has 74 main jets with 80 secondary jets.It has an 6.5 power valve,70 idle air bleeds,33 hi speed bleeds and 31 nozzles.I am running 6.5psi of fuel pressure and the float level is set just a hair over the bottom of the sight glasses.It hasnt used much oil as far as I can tell but it hasnt been run but maybe 6 miles around the house and 7 1/8th mile passes.Yes it seems to have a good seal around the carb and spacer.

Jerry is very much right about many things . You can pull your valve covers and try to wiggle the valves side to side by the top of the retainers to see if there is play in the stems to guides . This is one way how I check used cyl heads when buying them localy . Most of the seal that I see are 531 but if you have .531 seals on a .500 boss . Your talking -031 the positive seal will never fit tight . They would act like umbrella seals . Then again you should be able to see this with the valve covers off. I buy bare heads and assemble them at home . I do buy good S/S valves chrome moly retainers VTO positive seals and heat-treated locks . I also hand Lap each valve to its seat . I never had a loose guide to stem . But I had many that where to tight and I had to open slightly -002 . But with all the Import part you might have some under size stems . I have been lucky not to have had this problem . The thing about the PCV valve it can be on the right side or the left side . But if it sucks oil it will bring it to the intake were it will be giving to all the cylinders. I had it happen to me on a 1974 Z28 with a built L82 that I would rev 8000 RPM . At the end of the track that thing would suck up oil and foul all the plugs . I like PCV valves but not on a race car .

Tango

On the pcv I was referring to right or left as in a dual plane manifold where it could effect 4 cylinders and not the other 4

Where in the Windy City are you?

Jerry

Originally Posted by DennyW

Must be an echo in here.

HELLO,HELLO!!!

Originally Posted by jerry clayton

Tango

On the pcv I was referring to right or left as in a dual plane manifold where it could effect 4 cylinders and not the other 4

Where in the Windy City are you?

Jerry

25 miles east of you . And if the PCV is hooked up to the carb ? All 8 get oilled . Mine did !