Identifying Pontiac cylinder heads is also a fairly straightforward procedure. This process is made easier since the majority of Pontiac cylinder heads have the casting number, or a portion of it, on the outside of the head (as opposed to under the valve cover like many other makes). Determining which head you’re looking at is as simple as reading the casting number and the date code — usually.
Some heads are missing either the casting number, (an example would be early production ’68 Ram Air II heads or some ’73 Super Duty heads), while others are missing date codes (’69 Ram Air IV and ’70 Ram Air IV cast before November, 1970).
Most of the time, however, both date codes and casting numbers are found on the heads. Early heads often used the entire casting number which is typically seven digits. Later heads (from the mid-Sixties on) usually used only the last two or three digits of the casting number. These numbers are usually found on the exhaust side of the head, either just below the valve cover rail, on the center two exhaust ports or on the end exhaust ports. Some heads carried the casting number (or a portion thereof) below the spark plug holes between the center and end exhaust ports.
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).
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Machined combustion chambers are a unique feature of Pontiac cylinder heads. When GM mandated a corporate-wide drop in compression ratios for the 1971 model year, Pontiac obliged by greatly increasing the size of the chambers. Compare the ‘72 455 H.O. (8.3:1 cr) chamber on the left to the ‘70 400 (10.5:1 cr) chamber on the right. Upping the compression on a Pontiac V8 is as simple as bolting on a ‘70-or-earlier head.
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| Beginning in 1968, Pontiac fitted their highest-performing engines with heads featuring redesigned round exhaust ports (shown above). Engines so equipped were the ‘68 Ram Air II 400, 1969-70 Ram Air IV 400, 1971-72 455 H.O., and 1973-74 Super Duty 455. The more standard “D-port” exhaust arrangement, shown below, is still a capable performer in all but the most extreme applications.
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Correctly identifying Pontiac cylinder heads is a particularly useful skill when planning your engine combination. Putting large-chamber 455 heads on a 400 is certainly not the way to go (the compression ratio would be down in the sixes), while swapping ‘70-or-earlier 400 heads onto a 455 would result in an 11:1 engine that would be tough to feed on today’s gas. |
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| FYI: Date codes can usually be found just below the valve cover rail on the exhaust side of the head. One exception is the previously mentioned Ram Air IV heads of ’69 and early ’70. These heads were actually cast with a date code, but the code was located under the valve cover between the two center cylinders. This area was then machined for the head bolt, which removed the casting date! This slight oversight was fixed on Ram Air IV heads cast after November, 1970.
One important point to keep in mind when identifying cylinder heads is that certain partial casting numbers can be found on more than one type of head. For example, casting # 16 is found on four different types of cylinder heads, although none of the same year. This is why it’s important to find the date code along with the cylinder head cast number, otherwise mis-identifying is very likely.
The date code format used by Pontiac on cylinder heads is the same as that used on blocks; the month of production is coded as a letter (A=January, B=February, etc.), followed by one or two digits which are the day of the month, and ending with the last digit of the year in which it was produced.
The chart at the end of this article shows cylinder head casting numbers and their original applications. Swapping cylinder heads between applications is a good way to juggle compression ratios and change the performance characteristics of an engine. Don’t forget, though, that heads used up to 1964 oiled the valvetrain through the rocker arm studs, and that Pontiac changed the valve angle in 1967. To be safe, head swaps should take place only among those of the same generation (Pre-1964, 1964-66, 1967-and-later except 301 and 267). |
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