GM Head Questions

Michael Pliska · 05-30-2009, 11:20 AM

I'm hoping someone on here can help me answer some questions. I have a set of aluminum cylinder heads I bought many years ago, finally went to use them and the pistons don't have enough clearance with the chambers. I initially thought that they must be closed chamber instead of open chamber, but the info I've found so far indicates that they are open chamber.

The castings are #3946074, date codes 11 14 73 & 7-10-74. I'm wondering if they have been surfaced significantly. Are there any standard measuring points to check for how much heads have been surfaced?

Would it work to use thick copper head gaskets to get the clearance I need?

I also noticed that they have more of a "D" shaped exhaust port. Is this typical for this vintage of castings? The photos of the "D" shaped ports I could find online also showed a ridge in the port floor, but mine do not have that.

These have the holes for 2 extra head studs, apparently for aluminum blocks, but have been plugged with pipe plugs.

Photos below:

Regards,

05-30-2009, 11:20 AM	#1
Michael Pliska Member Join Date: Oct 2008 Location: Happy Valley, OR Posts: 260 Likes: 0 Liked 0 Times in 0 Posts	GM Head Questions I'm hoping someone on here can help me answer some questions. I have a set of aluminum cylinder heads I bought many years ago, finally went to use them and the pistons don't have enough clearance with the chambers. I initially thought that they must be closed chamber instead of open chamber, but the info I've found so far indicates that they are open chamber. The castings are #3946074, date codes 11 14 73 & 7-10-74. I'm wondering if they have been surfaced significantly. Are there any standard measuring points to check for how much heads have been surfaced? Would it work to use thick copper head gaskets to get the clearance I need? I also noticed that they have more of a "D" shaped exhaust port. Is this typical for this vintage of castings? The photos of the "D" shaped ports I could find online also showed a ridge in the port floor, but mine do not have that. These have the holes for 2 extra head studs, apparently for aluminum blocks, but have been plugged with pipe plugs. Photos below: Regards, __________________ Michael Pliska 643 S/G Last edited by Michael Pliska; 05-30-2009 at 11:23 AM.