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Tkimble01 Feb 6th, 06, 9:10 PM Recently I had my 454 rebuilt for my 68 Chevelle SS. The ID number on the heads are 3909802 date coded D67. I was told they are very desireable GM heads. I looked the number up and they came up as 1966-1967 396/427 heads. Why are these heads desireable? I am not a GM head expert. If I were to guess I imagine they are oval port closed chamber. Anyone else have any ideas. Thanks Tom Sams454SS Feb 6th, 06, 10:37 PM From information I gathered from "How to rebuild your Big Block Chevy" here's what they have listed.....Those heads are 396 heads which came on 65-66 375/425HP 65 only and also on 375 HP 66. They have 2.06/1.72 Valves and a small 96.4 cc combustion chamber volume. From the horsepower rating of the engines they came off of I would assume they are pretty good heads....sounds like a closed chamber to me for a high compression motor.....although the valves are small I would also think they are oval port heads. They would probably perform even better if they were machined for larger 2.19/1.88" valves. Mike Feudo Feb 6th, 06, 10:55 PM They are oval not big port so they came on either the 350 or 325 hp 396 not the hi-po motors. They are the small chamber heads that can have shrouding problems because of the narrow chambers but for a mild 396 they do work well. 502scs Jun 10th, 06, 5:09 PM I also have a motor with those heads on it. Will probably be selling them and rest of the parts. Exactly the same 3909802 / D67 :-) Recently I had my 454 rebuilt for my 68 Chevelle SS. The ID number on the heads are 3909802 date coded D67. I was told they are very desireable GM heads. I looked the number up and they came up as 1966-1967 396/427 heads. Why are these heads desireable? I am not a GM head expert. If I were to guess I imagine they are oval port closed chamber. Anyone else have any ideas. Thanks Tom Tkimble01 Jun 11th, 06, 8:03 AM What do you read these heads as? I received two different answers. Thanks Tom mr 4 speed Jun 11th, 06, 8:08 AM oval port,closed chamber decent heads..I run a similar head on my 454,last 3 digits are 215's Busted Knuckles Jun 11th, 06, 9:47 AM Yours are true closed chambers. Chris' heads are "semi-closed" where material under the plug has been relieved a bit. Yours are as small chamber as ever built, can be made to flow decent with proper chamber work and big valves. Best thing about 'em is how easy it is to get compression out of 'em. | ||