I have a 69 340,X heads, stock hp exhaust manifolds air gap performer intake and comp cam pp284h cam 0.484 lift. 4 speed car with a 355 rear end. I have a holley carbureter 80778 700 cfm carb that needs rebuild. currently 69 jets in front and 78 in rear. 6.5 power valve can any one give some suggestions on jet size and power valve size? a local carb man said I should change the power valve to a 4.5 because of cam.
Carburetor help
- Thread starter slx70
- Start date
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Marcohotrod
Well-Known Member
you want to start off with factory holley jets and go from there, try to figure if it is rich or lean. for that cam 6.5 p v is probably right, to check use a vacuum gauge or check for any stumble on acceleration or very rich at idle
65Val
Average Length Member
Power valve size is usually 1/2 your vacuum reading at idle, eg; 10in. vacuum ~ 5.0 power valve. Local guy's in the ballpark.
yellow rose
Overnight Sensation
Don't use idle vacuum to pick power valve opening. Drive the car and measure the vacuum at a cruise and set the number about 3-4 numbers under cruise vacuum i.e. cruise vacuum is 14 set the PV to open at 8.5 because the PV can be open at idle, it just can't be blown.
Mark Whitener has a great video on it on YouTube. Google it and watch the video.
mopardart44067
Well-Known Member
I'm interested on your impression of the pp284h because the mopar 284 purple is twice as much.
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