400 GTO heads on a 326 Tempest? - Pontiac GTO Forum
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post #1 of 3 (permalink) Old 05-19-2018, 05:09 PM Thread Starter
 
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400 GTO heads on a 326 Tempest?

Hello. I have a 1966 Tempest with a 326 2 bbl. I had an older guy tell me that he had a set of number 16 heads off of a 1969 GTO 400 ram air III that I could put on my 326 Tempest. Now I know that most Pontiac engines can use the same parts from 326 all the way to 455. My question is would those heads work on my 326 or would they be to much for it?
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post #2 of 3 (permalink) Old 05-19-2018, 07:17 PM
 
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Originally Posted by Btree View Post
Hello. I have a 1966 Tempest with a 326 2 bbl. I had an older guy tell me that he had a set of number 16 heads off of a 1969 GTO 400 ram air III that I could put on my 326 Tempest. Now I know that most Pontiac engines can use the same parts from 326 all the way to 455. My question is would those heads work on my 326 or would they be to much for it?
The 326 bore (3.71875") is too small and the #16 intake valve is too large - it will hit the block. On the 1969 350HO, the #48 heads with the larger valves was used, but the top of the cylinders were notched from the factory to allow for this. The bore of the 350CI is also a little larger (3.875") than the 326 to begin with.

Additionally, the valves were moved outward to accommodate the larger valves and the valve angle was changed in '67 along with matching pistons, so the later heads would require the correct pistons with corresponding valve notches to avoid any valve-to-piston interference.

I believe the 1.94" intake valve can be fitted to your heads to give a little more breathing. Then give it a 3-angle valve job for increased flow. It is a closed chamber head said to be 68 cc's, but they are typically a few cc's larger. Take a look at the specs for the 326HO which had an advertised HP of 285. You won't wind up with a killer engine like a 400 or 455, but the 326 can be a zippy engine that will put a smile on your face. Dad's '65 Impala with the 195HP 283 and three on the column was a pretty zippy car to drive. Second gear was my favorite 'cause it pulled hard & fast.
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post #3 of 3 (permalink) Old 05-19-2018, 07:30 PM Thread Starter
 
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Ok thanks for the information. I knew I wasn’t going to get any crazy hp with the 326 but I just wanted something to surprise some people
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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