Two different heads on my 1970 GTO

Goatboy · Veteran Member

Two different heads on my 1970 GTO

87 player bird · Poncho Master!

There is another thread about this on a different board, seems the # was miss cased on that link, dunno about yours though. As long as the valves,guides, etc.. are the same, should not be a problem in my opinion. 1 head not close chamber, the other open chamber are they? Not too familier with BBP as I've only done 1 always been a bowtie guy. Mine the casting #'s were the same.

Goatboy · Veteran Member

Thanks, I'll check into it. I haven't even lifted the valve covers yet. I will check out that other thread. I guess anything is possible.

rabbit64cs · Canadian Poncho Superstar!

Year(s)	Engine	Code 12	Intake	Exhaust	Volume
62-62	389/421SD	544127	2.02	1.76	68
70	400RAIII	12	2.11	1.77	72

Year(s)	Engine	Code 13	Intake	Exhaust	Volume
70	400	13	2.11	1.77	72

should be no problems here, you can check the date code on the heads ,the 12 will be a 70 head, 62 would not bolt up.

-- Edited by rabbit64cs on Friday 17th of September 2010 09:57:02 PM

pontorquer · Poncho Master!

The 1970 Pontiac 400 head #12 and 13 are basically the same heads, I've seen 1975 Pontiac 400 6X head on one side and 5C on the other, same idea, I don't know why Pontiac did this on the assembly line, one of those mysteries ?

Highlander · Veteran Member

rabbit64cs wrotwhat i got
Year(s)
Engine
Code
13 Intake
Exhaust
Volume
70 400 13 2.11 1.77 72

should be no problems here, you can check the date code on the heads ,the 12 will be a 70 head, 62 would not bolt up.

-- Edited by rabbit64cs on Friday 17th of September 2010 09:57:02 PM

I have a set off late 60's Heads, the guy i got them from said they are 400 ram air Heads...how do i know for sure what i have?

Beaumont4008 · Uber Guru

Look at the casting number on the centre exhaust area as in fig 2. That number will identify the heads.

1-Certain heads, like this 1970 Ram Air IV, had the casting identification number on the end exhaust port. Still others would feature the number on the area just below the valve cover rail.

2-Most Pontiac cylinder heads feature an identification number cast into the external surface, which greatly simplifies identification. This number was usually the casting number, or a portion thereof. The area above the two center exhaust ports was a popular location for the casting numbers. 7F6 is the code for a 1972 455 H.O. head, while 13 is a 1970 330-horse (Firebird) or 350-horse (GTO) 400 head.

3-The head casting date is usually found on the exhaust side of the head just below the valve cover rail. These dates are read just like the block codes. The first letter identifies the month, the next one or two digits represent the day, while the last digit denotes the year the head was cast. C090 decodes as March 9, 1970 (this date code was taken from a 1970 #13 head).

Beaumont4008 · Uber Guru

Check out Wallace racing site for the list of casting numbers. See link below.

http://www.wallaceracing.com/head1.htm

Goatboy · Veteran Member

Thank you guys for all the information. I will just continue on towards getting this thing started. I will keep you posted on my progress.

Highlander · Veteran Member

Beaumont4008 wrote:

Look at the casting number on the centre exhaust area as in fig 2. That number will identify the heads.

1-Certain heads, like this 1970 Ram Air IV, had the casting identification number on the end exhaust port. Still others would feature the number on the area just below the valve cover rail.
2-Most Pontiac cylinder heads feature an identification number cast into the external surface, which greatly simplifies identification. This number was usually the casting number, or a portion thereof. The area above the two center exhaust ports was a popular location for the casting numbers. 7F6 is the code for a 1972 455 H.O. head, while 13 is a 1970 330-horse (Firebird) or 350-horse (GTO) 400 head. 3-The head casting date is usually found on the exhaust side of the head just below the valve cover rail. These dates are read just like the block codes. The first letter identifies the month, the next one or two digits represent the day, while the last digit denotes the year the head was cast. C090 decodes as March 9, 1970 (this date code was taken from a 1970 #13 head).

Thanks..I'll check that out tomorrow.

Highlander · Veteran Member

Highlander wrote:

Beaumont4008 wrote:

Look at the casting number on the centre exhaust area as in fig 2. That number will identify the heads.

1-Certain heads, like this 1970 Ram Air IV, had the casting identification number on the end exhaust port. Still others would feature the number on the area just below the valve cover rail.
2-Most Pontiac cylinder heads feature an identification number cast into the external surface, which greatly simplifies identification. This number was usually the casting number, or a portion thereof. The area above the two center exhaust ports was a popular location for the casting numbers. 7F6 is the code for a 1972 455 H.O. head, while 13 is a 1970 330-horse (Firebird) or 350-horse (GTO) 400 head. 3-The head casting date is usually found on the exhaust side of the head just below the valve cover rail. These dates are read just like the block codes. The first letter identifies the month, the next one or two digits represent the day, while the last digit denotes the year the head was cast. C090 decodes as March 9, 1970 (this date code was taken from a 1970 #13 head).

Thanks..I'll check that out tomorrow.

This is what i got..A8..

pontorquer · Poncho Master!

Frank, Are you sure it's not 48 ie. 1969 Ram Air III heads ?

Highlander · Veteran Member

pontorquer wrote:

Frank, Are you sure it's not 48 ie. 1969 Ram Air III heads ?

I'll go check.

Highlander · Veteran Member

Highlander wrote:

pontorquer wrote:

Frank, Are you sure it's not 48 ie. 1969 Ram Air III heads ?

I'll go check.

Yep your right..it's a 4 not A..lol..

Beaumont4008 · Uber Guru

Highlander wrote:

Highlander wrote:

pontorquer wrote:

Frank, Are you sure it's not 48 ie. 1969 Ram Air III heads ?

I'll go check.

Yep your right..it's a 4 not A..lol..

Good set of heads 72 cc chamber will give you over 10-1 compression.

Highlander · Veteran Member

That's good too know.. was it originally on a 400.. how much hp would that make? Here's the head casting date..A309.

unburt · Guru

The heads will work because of the chamber volume. They are identicle .
The #12 heads were used on manual tranny cars and #13 on auto equipped GTOs.
The heads were also used on 70 Grand Prix models.
Two years ago i ran #13s on my 400 and they work very well, but you have to pay attention to detonation because of the 10 plus compression.
Make sure your vacuum advance is set correctly and your total timing.
They work but your tune is important along with running good gas (octane)if you can get it.

Highlander · Veteran Member

Will they work on a 455 pontiac.

unburt · Guru

Yes they will work on a 455 but the compression will be higher still with the icreased bore size and thats bad territory.
The only way to get them to work is if you are doing a rebuild and go to a dished piston to lower compression.
I am running 72cc eldebrocks on a 461 stroker but i have 20cc dish pistons to keep me at 10.3.

the70judge · Guru

Usually its because someone needed a head so grabbed on that had the same cc's , I doubt Pontiac would do that and have a warranty issue

the70judge · Guru

unburt wrote:

The heads will work because of the chamber volume. They are identicle .
The #12 heads were used on manual tranny cars and #13 on auto equipped GTOs.
The heads were also used on 70 Grand Prix models.
Two years ago i ran #13s on my 400 and they work very well, but you have to pay attention to detonation because of the 10 plus compression.
Make sure your vacuum advance is set correctly and your total timing.
They work but your tune is important along with running good gas (octane)if you can get it.

# 12 heads are the 1970 Ram Air III heads for the Auto YZ block

lotsatas · Addicted!

unburt wrote:

Two years ago i ran #13s on my 400 and they work very well, but you have to pay attention to detonation because of the 10 plus compression.

Very very special attention ...........I have learned that the hard way.