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,

chris ok · 05-30-2009, 08:26 PM

they appear from pics to be angle milled quite a bit by looking at the accessory bolt holes. intake valve is a bit out of chamber looking too.

Michael Pliska · 05-31-2009, 01:57 AM

Thanks, I was wondering of those two end bolt holes are normally the same distance from the deck surface.

The intake valves do protrude about 0.030" past the deck surface.

FED 387 · 05-31-2009, 08:32 AM

that head is for a 69-71 Chevy 396/454 ---- 219 In /188 Ex ---118 CC chamber--- L-88/ZL-1/LS-6 with Rectangular intake port

Michael Pliska · 05-31-2009, 12:24 PM

Assuming the two accessory bolt holes were originally the same distance from the deck, it looks like they have had an angle cut equal to 0.86° (the holes are 6.72" apart, and the exhaust side one is 0.101" closer to the deck surface). Is this a typical angle cut?

Thanks,

427_ED · 05-31-2009, 04:58 PM

Sell those to a restoration guy. Buy a new set of "401" heads. You'll probably come out $$$ ahead.

Bob Pagano · 05-31-2009, 05:21 PM

Dont waste your time on old tech.........use the new heads like Ed said

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.

05-30-2009, 08:26 PM	#2
chris ok Senior Member Join Date: Jul 2002 Location: Long Island, New york Posts: 592 Likes: 131 Liked 46 Times in 29 Posts	Re: GM Head Questions they appear from pics to be angle milled quite a bit by looking at the accessory bolt holes. intake valve is a bit out of chamber looking too.

05-31-2009, 08:32 AM	#4
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,419 Likes: 528 Liked 332 Times in 180 Posts	Re: GM Head Questions that head is for a 69-71 Chevy 396/454 ---- 219 In /188 Ex ---118 CC chamber--- L-88/ZL-1/LS-6 with Rectangular intake port

05-31-2009, 12:24 PM	#5
Michael Pliska Member Join Date: Oct 2008 Location: Happy Valley, OR Posts: 260 Likes: 0 Liked 0 Times in 0 Posts	Re: GM Head Questions Assuming the two accessory bolt holes were originally the same distance from the deck, it looks like they have had an angle cut equal to 0.86° (the holes are 6.72" apart, and the exhaust side one is 0.101" closer to the deck surface). Is this a typical angle cut? Thanks, __________________ Michael Pliska 643 S/G

05-31-2009, 04:58 PM	#6
427_ED Member Join Date: Apr 2009 Location: Nicholasville, KY Posts: 265 Likes: 54 Liked 2 Times in 1 Post	Re: GM Head Questions Sell those to a restoration guy. Buy a new set of "401" heads. You'll probably come out $$$ ahead.

05-31-2009, 01:57 AM	#3
Michael Pliska Member Join Date: Oct 2008 Location: Happy Valley, OR Posts: 260 Likes: 0 Liked 0 Times in 0 Posts	Re: GM Head Questions Thanks, I was wondering of those two end bolt holes are normally the same distance from the deck surface. The intake valves do protrude about 0.030" past the deck surface. __________________ Michael Pliska 643 S/G

05-31-2009, 05:21 PM	#7
Bob Pagano VIP Member Join Date: Jun 2002 Location: New Holland, PA Mooresville,NC Posts: 1,163 Likes: 240 Liked 16 Times in 11 Posts	Re: GM Head Questions Dont waste your time on old tech.........use the new heads like Ed said __________________ Bob Pagano A/SA