Which one should I use in a Holley 1850 thats going on a mild 350? I just bought the carb at a swap meet, and Im planning on rebuilding it and replacing the power valve as cheap insurance, but I dont know which one to get. Also can you tell if it is good or bad just by looking at it, or does it have to be running on the car?

 

Measure your vacuum at a low idle. Halve the number and add 0.5. This should get you pretty close to right power valve. If your vacuum is 12in hg you need a 6.5. You can test a power valve by sucking on it.

 

Holley rebuild/Trick kits come with a new powervalve. It's a 6.5", which is what pretty much every holley comes with. It's a fairly safe bet 6.5" is close enough for a mild engine. Even if it isn't, I always tune the powervalve opening last anyway.

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just use 1 6.5" in it i had this carb and that stock for it!

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 intake.

Future mods performer rpm air gap intake (polished) and 600 edlebrock carb, comp roller cam, and way better headsa 400 defintely in the works!