# '65 GTO cylinder head identification



## Roqetman (Aug 31, 2015)

I'd like to identify the year cylinder heads on my 65 GTO. The engine block casting code, date and production number are correct and are verified by the Protect-o-Plate. However the cylinder heads do not appear to have any markings on the center exhaust port. The number I did find is directly under the valve cover gasket between the center and front exhaust ports and appears to be 0159D. The 159 is very clear, the 0 and D not so much. Also, there is a G on the front and an L on the rear exhaust port (passenger side).
Any help would be greatly appreciated. Thank You!


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## PontiacJim (Dec 29, 2012)

Look for a 6 digit casting number - might be in the rocker arm area under the valve cover somewhere. The first 3 digits identify the year.

Closed chamber head? or open chamber? Need a photo.

What size are the valves?

Does the intake gasket mating surface look like the 1965 and up configuration or the 1964 and down? Need Photos.

It may be the nearness of your photo, but are both spark plugs the same size? One looks like a large plug while one almost looks like a smaller "peanut" plug.

More photos needed on this one.


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## Pinion head (Jan 3, 2015)

Externally dated D159 Pontiac V8 head with the machined bosses for AC mtg bracket will be a '69 model head. '70 model head castings will start showing up with early Fxx9 dates.

To ID, look at the center exhaust port area on each head, there should be a pair of raised numbers: 46, 47, 48, or 62. One of those numbers will the casting number. All are open chamber heads. 48's and 62's had their own style guide plates with screw in rocker studs going through the guide plates. #46 (400 small valve) & #47 (350 small valve) were originally used on 2 bbl engines, both casting numbers of heads originally had press in studs. 

If no casting numbers on the center exhaust area, they have been removed, and will take a little more investigation. Under the valve cover of a well cleaned head, with all the rocker arms removed, might take a few good pics. In the 80's, there was a fellow in my area that would alter the casting number on casting #46, #47, and '70 model #16 heads and list them in the paper, for sale, as "Ram Air" application heads. To his credit, he did change the heads over to screw in studs and machined them for stock big valves, knowing what to specifically look at, at least two of us figured out what several pair of Richard's heads started out as.


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## Roqetman (Aug 31, 2015)

Upon further investigation, it appears that there is a raised "4" or "A" on the center exhaust outlet, cannot make out any other number on the outside of either head, except for the "159" stated in earlier post. The car does have factory Air Conditioning. Does this help or do I need to take the valve covers off? I can send pictures tomorrow if needed. (BTW, the spark plugs are the same size and are soon to be replaced.)


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## Pinion head (Jan 3, 2015)

Ck both head's center exhaust ports, I'd use a stiff wire brush. No 4A's on Pontiac heads, 4A is the identifier on 403 olds heads, but in a different spot. 

After a good wire brushing the casting number should be come more evident, either a 46, 47, or 48. 48's were the only "4 something" factory screw in rocker stud head for '69 models, but as mentioned earlier, quite a few 46's and 47's have been upgraded to screw in studs.


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## Roqetman (Aug 31, 2015)

Hello Pinion Head, thanks for the info, apparently my heads are from a '69 w/AC. I took some pics of the valve train and center exhaust outlet that I'd like to have you look at to see if you can help determine if these are the good flow heads or not. They must from a 400 since 389 were not made in 69. I've tried several times to spend the pics but I'm having difficulty getting them to send on this forum. If you don't mind, please send your email address and I will send the pics. Thanks! My email is [email protected].


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