I started checking the numbers on my 1970 GTO Ram Air III to see what might still be original, only to find that the driver side head is a 12, and the passenger side is a 13. The motor has not been run since it was "rebuilt" a few years before I bought it. A carb is the only thing in my way before trying to start it, as it did not come with one. I just finished re-wiring the engine because it was a mess. My question is; could this set up even work? I have never heard of someone running two different heads. I do have a parts car with a 400 motor as well that has 6x heads. Maybe rebuilding those might be the safest way to go? I would hate to somehow ruin those other heads in case I can find the matching ram air head in the future. Any thoughts would be appreciated.
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.
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 ?
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).
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).
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).
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.
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.
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
