Pretty straight forward question here. Will a large can like the cc306 or gm847 with stock heads raise the r.p.m at which you make peak power? The reason i ask is because i had a xfi280 c.a.m on a set of non ported castings that was making peak power at 58-5900 r.p.m.s. is it because the heads don't have the volume or velocity to flow enough to pull power to 6500+?

 

I made the mistake of running an XE 236/242 on stock heads and boy was it a disaster. The car made no power down low and peetered out by 6200, tops.

You have answered your own question. If the heads can't support the air/fuel flow produced by the new cam events of course it won't make power in the higher RPMs.

 

I had the xfi280 with ported heads though and it pulled hard all the way to about 6600, ran a best of 11.63 @116 with it.

 

im running a comp cam 525/525 236/242 on stock heads with aftermarket valve springs an 1.6 full roller rockers an ported intake.been that way for 2 years.best on motor was 12.30 an a 125 shot was 11.55.still runs great an daily driven.

 

The question was based on my current setup with nitrous. My power always fell flat at 5800. The heads were milled 30 thou and the block was zero decked. I can't seem to track down the dyno graphs but i know even with the Nos it still fell flat right around 5800-5900. Now that i have a set of le3 heads with the 205cc runners and still a true 54cc combustion chamber I was assuming it would have slightly less compression but be able to pull well past 6k with or without the Nos. My boosted plans are on hold as I ran into an issue money wise too build the short block but my intentions were to use my le3 heads with a custom ground c.a.m setup for boost and nitrous in the future.

 

Did it make power to 6600 on a dyno or feel like it was still pulling hard up top? I know a dyno is a tuning tool but i still should be pulling into the 6k+ range especially with the spray. I made 503 ft lbs with a 150 shot at 3800. Only made 389rwhp @5800 with a 150 shot which to me seems extremely low