i'm going to be running a ZZ4 cam with world products 305 heads on a 5.7liter.the heads have runner size of 171cc(cast iron heads 155cc,aluminium heads 163cc)and a 58cc cumbustion chamber.1.25 CranCams springs(good up to a .600 lift).the heads will except up to .560 lift.the lift #'s on the ZZ4 cam are .474 intake and .510 exhust.with 1.5 RR's those #'s jump up to .504 intake and .540 exhust.with 1.6 RR's that goes up to .514 intake and .550 exhust.now my question is with those heads with will make more power?keep in mind i WILL be useing this heads!!!what can i do to make this work?

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1991 banditt2 #130 of 600
Project 350 Banditt
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I think you meant with 1.6's they go up to .505/.540. With 1.65's its .521/.561

If the heads are still flowing good numbers up to those points, get the higher ratio rockers. But, for example, if the heads flow their best at .500 lift, pushing the valves to .550 wont help, and might hurt. Make sense?

For the record, I used 1.65's on the intake (I thought they were 1.6's) and 1.52's on the exhaust (thought they were 1.5's), with my ported L98 heads.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
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go with as much rocker ratio as possible. AS long as you don't get spring bind, valve-piston contact, or retainer-valveguide contact then go for it. If the retainers hit the guides then just grind the guides down lower. With the right length pushrods the bigger rockers should work fine for you.

 

just to clarify.the lift #'s are .474 intake and .510 exhust on the ZZ4 cam.what are the #'s going to be with 1.5 and 1.6 RR's?

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1991 banditt2 #130 of 600
Project 350 Banditt
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The .474 & .510 lift numbers ARE with 1.5 rockers. 1.6 rockers increase the lift to .505/.544 That is a lot of lift for a 350 TPI.

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87 Formula 350 13.94@96.67
98 Z28 1LE 13.15@107.59
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