My brother is getting me some Comp Magnum 1.6 RRs for me, to put on with my new heads I will be getting, Pro Lightnings, it looks like now.

Anyways, I have the comp 268xe cam .477/.480 stock lift, what will this raise my lift too, and how much HP will you think I can see out of these, as Comp says 15-30, but we know how that goes. Thanks.

 

0.477" is stock lift at the valve with 1.5 rockers.

first, divide out the rocker ratio
0.477 / 1.5 = 0.318

thus 0.318" is the lift at the cam lobe

now, multiply back in the 1.6 rockers
0.318 * 1.6 = 0.508

so effectively you will have 0.508" lift on the intake.

 

thanks.

so, 1.6s will work then? I've heard about clearance problems sometimes.

 

no way to know. every setup is unique. have to assemble it and then observe it.

case in point, my 406/fastburn/mechanical roller/crane roller rocker setup required non-stock length pushrods, and further the rocker arms touched the valve covers (GM black crinkle-coat style) on the vertical wall of the valve cover nearest the intake (NOT the top of the valve cover). you just never know until you try.

 

Forget the lift calculations. Where do you find a brother like that??

Also, you should understand that the effective duration at 0.075" valve lifts will be increased slightly as well. An easy way to calculate the lift increase is to multiply the net valve lift with 1.5:1 rockers by a factor of 1.066667 (1.6 / 1.5). Calculating the duration change requiressome knowledge of the ramp angles and lobe profiles, but generally the increase is only about 1.8%, intake and exhaust.

 

Wow, you lost me on that one, is that good?

Yeah, he said merry xmas to me, I had some other summit ones but there might be a little damaged.