Head CC ?

Chipper Chapman · 04-19-2013, 09:26 PM

In a conversation with a friend, he mentioned his late 70's 350 stocker is allowed to have a 624 head, milled to 63.3 cc. I questioned how it is that the spec is so small for a head always known as a 76cc smog head? So I got looking around, the same exact head is only allowed to be 73.7 cc on an 86 truck 350, which is far more realistic. GM only made the one 462624 casting (excluding the newer hecho en mexico) So does anyone know why such a large difference?

Mike Taylor 3601 · 04-22-2013, 08:25 AM

882's on 350's on 73,74,75 nova's are changed to 64ish cc from 76,my brother has one been sitting for 7-8 years now, but when we did it we had to angle mill .160 on his heads.
I don't know why it is changed that much we called and double checked that it was'nt a misprint .
Mike Taylor 3601

Billy Nees · 04-22-2013, 09:18 AM

Quote:

Originally Posted by Mike Taylor 3601

I don't know why it is changed that much we called and double checked that it was'nt a misprint .
Mike Taylor 3601

I think that you'll find that the "misprint" came about in around 1971!

Mike Taylor 3601 · 04-22-2013, 12:23 PM

I remember the spec sheet we had back then around 95-96 showed head cc revised to 64ish I think it was 63.3 and we put on 64 had revision date for the spec but can't remember date.
Or did you mean they changed the spec starting with 71 cars Billy?Which would sound right because 70 probaly had 64cc heads
Mike Taylor 3601

Jeff Lee · 04-22-2013, 12:27 PM

There are numerous examples of "smaller than real life" combustion chamber cc's published in the NHRA Engine blueprint specs. Maybe these will be corrected one day...

Chipper Chapman · 04-22-2013, 10:55 PM

Does anyone remember the 215 casting bbc head being 116cc in the early 90's? My dad swears thats what his had to be, but for a while now they claim 96, like the bathtub chamber heads should be.

Dwight Southerland · 04-23-2013, 06:37 AM

I have a tech sheet from 1983 that shows the BBC 215 head listed as a replacement for a 1967 396-325 and a 96 cc spec. When you have replacement heads assigned to an engine, the original specs for the engine as received from the mfr is generally what is the rule, not the characteristics of the head itself. Mid-60s 327 Chevs use the "double hump" series of heads - 461, 462, 291, 186, 041 - yet use a 57.5 cc spec. We all refer to those heads as "64 cc" heads and rightfully so because that is the manufactured characteristic. What you really need to question is the specs in the book and the source; some did not come from the mfr.

04-19-2013, 09:26 PM	#1
Chipper Chapman Member Join Date: Jan 2004 Location: Belmont N.S. Canada Posts: 473 Likes: 246 Liked 166 Times in 71 Posts	Head CC ? In a conversation with a friend, he mentioned his late 70's 350 stocker is allowed to have a 624 head, milled to 63.3 cc. I questioned how it is that the spec is so small for a head always known as a 76cc smog head? So I got looking around, the same exact head is only allowed to be 73.7 cc on an 86 truck 350, which is far more realistic. GM only made the one 462624 casting (excluding the newer hecho en mexico) So does anyone know why such a large difference?

04-22-2013, 08:25 AM	#2
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,371 Likes: 352 Liked 304 Times in 102 Posts	Re: Head CC ? 882's on 350's on 73,74,75 nova's are changed to 64ish cc from 76,my brother has one been sitting for 7-8 years now, but when we did it we had to angle mill .160 on his heads. I don't know why it is changed that much we called and double checked that it was'nt a misprint . Mike Taylor 3601

04-22-2013, 12:23 PM	#4
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,371 Likes: 352 Liked 304 Times in 102 Posts	Re: Head CC ? I remember the spec sheet we had back then around 95-96 showed head cc revised to 64ish I think it was 63.3 and we put on 64 had revision date for the spec but can't remember date. Or did you mean they changed the spec starting with 71 cars Billy?Which would sound right because 70 probaly had 64cc heads Mike Taylor 3601

04-22-2013, 12:27 PM	#5
Jeff Lee VIP Member Join Date: Jul 2007 Location: Anthem, Arizona Posts: 2,766 Likes: 0 Liked 3 Times in 3 Posts	Re: Head CC ? There are numerous examples of "smaller than real life" combustion chamber cc's published in the NHRA Engine blueprint specs. Maybe these will be corrected one day... __________________ Jeff Lee 7494 D/S '70 AMX

04-22-2013, 10:55 PM	#6
Chipper Chapman Member Join Date: Jan 2004 Location: Belmont N.S. Canada Posts: 473 Likes: 246 Liked 166 Times in 71 Posts	Re: Head CC ? Does anyone remember the 215 casting bbc head being 116cc in the early 90's? My dad swears thats what his had to be, but for a while now they claim 96, like the bathtub chamber heads should be.

04-23-2013, 06:37 AM	#7
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 2,000 Likes: 64 Liked 777 Times in 193 Posts	Re: Head CC ? I have a tech sheet from 1983 that shows the BBC 215 head listed as a replacement for a 1967 396-325 and a 96 cc spec. When you have replacement heads assigned to an engine, the original specs for the engine as received from the mfr is generally what is the rule, not the characteristics of the head itself. Mid-60s 327 Chevs use the "double hump" series of heads - 461, 462, 291, 186, 041 - yet use a 57.5 cc spec. We all refer to those heads as "64 cc" heads and rightfully so because that is the manufactured characteristic. What you really need to question is the specs in the book and the source; some did not come from the mfr.