I spoke to Brian at Ebert's Engine Service in New Orleans(ebertsengine@msn.com). He did the machining on the heads installed on my 400. He explained that he DID mill down the heads, deburred and polished the interior surfaces, added hardened seats, multi angle valve job, added bronze guides and polylocks, standard rockers, lifters, and standard size valves for the #62 heads. He expected the compression ratio to be right at factory spec.
He also added that the deburring and polishing goes a long way as far as avoiding detonation, especially on Pontiac heads. I run pump premium with no problems. I'm sure he'd be glad to answer your e-mail directly if you have any specific questions. I definitely recommend his work!
I'm a hobbyist. Not a professional. Don't be hatin'!
