Pat....you nust have mis read my original post. I'm using Dart 335 CNC.....not 355...heads. The build is a GenVI 454 4 bolt block, bored +.060 to 4.310 and stroked to 6.385 to 496 c.i. The rotating assembly is Eagle 4340 w/ H beam rods, J&E 13.5:1 forged pistons gas ported w/ total seal rings. The camshaft is a solid roller by Erson.....approx. .765 lift....310 duration....don't have the specs in front of me. The lifters are Lunati, Jessel shaft mounted rockers, the Dart heads, which I mentioned......with matched Dart intake, and Quick Fuel 1150 Dominator. Also using MSD distributor, locked for no advance, 6AL plus box. The timing is definitely 40 degrees. I have bumped it down to 38 at times, but lose a little 1/4 mile speed when that is done. Also....it tends to run even a little hotter....quicker...when retarding the timing. The cam was degreed by a professional builder, and the motor runs very strong, so I don't suspect any errors there. Keep in mind.....I don't consider myself to be an accomplished big block Chevy guru by any means, but I know my way around engines.....I've assembled several small blocks. I'm really not very famiiar with big block Chevys....that's why I'm here. Thanks for any additional input.