Originally Posted by cobalt327
These heads are all similar. Prolly not a 5 hp difference between them as long as the are prepared the same. The 041 is supposed to have a little more meat under the spring seat and is "stealthy" in that it doesn't have the double hump identifier.
Pay attention to the compression ratio- a 64cc chamber on a 400 SBC w/flat tops and a tight quench can exceed 11.5:1- higher than pump gas will allow w/o detonation. A 22cc dished piston will put you at about 9.75:1, the absolute limit I would recommend using iron heads- and even then the cam has to be chosen carefully so the dynamic compression ratio isn't too high.
Static compression ratio
Dynamic compression ratio
*United Engine & Machine Co. Incorporated
You should CC the heads to be sure that each pair are the same, and that none were milled excessively. Even if they are as cast
and never been milled, the chamber volumes can vary from published figures.
Thank you for the great info and for the links. I pulled the tunnel ram off and actually had 4 lifters that were bad, just not bleeding down as fast like that one. I checked my cam lobes and they checked good and also looked very nice and broken in by looking through the lifter bores. I used Isky cam lube on the flats of the lifters, after soaking them in 30W oil overnight, and put em in and got the Stealth intake on I'm gonna run temporarly. I had to stop as the Ala. vs LSU game was about to start, watching it now lol. I hope to get the impala finished up tomorrow and get started on the motor swaps i've got lined up. I wrapped the 400 up and plan on using it in an S10 build I plan to do soon. I will be reading about CR before I make my decision on which way to go.