what size spring should i run with a stock engine with a pfab log, precision 5857, gunna run around 14psi boost

 

Bov or wastegate?

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According what to what my builder has said, it depends on what type of vacuum the manifold is pulling.

 

blow off valve! yea i heard that also about idle vaccuum. but then why would the amount of boost you run affect the spring size.

 

Bov runs off vacuum .waste gate runs off boost. Go to tials spring pressure sheet and find the one for 20-22" of vac. That's the spring you want. I think it's the unpainted one but I could be wrong so check for your self

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^^^ yea the unpainted one is the one to put in.

Yellow spring for -21 to -23
Plain spring for -19 to -21 which is what our manifolds usually pull in vacuum.