Stage 2 cam ?

sccrewzer

Registered User
So I finally got this car turned on I know the engine has stage 2 cam and heads from coy miller. My question is would the cam affect my vacuum cause my stock bird at idle the vac is around 22-24in-hg this bird at idle is 12-15in-hg.
 
So I finally got this car turned on I know the engine has stage 2 cam and heads from coy miller. My question is would the cam affect my vacuum cause my stock bird at idle the vac is around 22-24in-hg this bird at idle is 12-15in-hg.

As far as I know, the larger lift of the cam, the greater loss of vacuum at idle.
 
That would explain it. thanks for the answers. second ? and more to come as I try to revive this beast.
 
My vote is Lobe Separation Angle has a major affect on vacuum

Yes, you are correct. Increasing Duration without changing the Lobe Seperation just increases the overlap. Lobe Seperation directly effects the amount of vacuum...
 
Tks Dave

Will take a couple of reads to fully sink in.

Can't find factory cam LSA in manual. Presuming 114 or 116

Yes, Somewhere in that range. Probably the higher of the two for better idle quality. Study the theory behind each till you fully understand it. Then learn how each effects the engine performance themselves. That makes it easier...
 
So with 218/224 112 lsa I will be running pretty low? (motor not installed yet)

My old .520 lift cam had 218/224 duration 112 lsa and it had good vacuum. My new .600 lift cam has 230/236 duration and 112 lsa and vacuum at idle is low, low enough to make the brake pedal hard as a rock but a with a little rpms the vacuum comes up and the brakes feel fine.
 
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