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Discussion Starter #1
Good morning All, I have run into a little problem, while dismantling my 68-400 engine and checking dates and numbers I discovered my left side exhaust manifold was from a 69 (9782810-a) date code J029.

Will this exhaust manifold restrict flow on my 68? I have noticed the ports on the 1 and 5 cylinders is fairly small and round compared to the head. the head matches the engine and the car.

Does nay one know where I might be able to purchase a correct 68 manifold.
Hope the water is nice where you are today.
Enjoy
 

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Wallace has the casting numbers. Your left appears to be a 1969 GTO, so most likely the same as the '68 ports. Pontiac Exhaust Manifolds - Wallace Racing

Measure the outlet size to see if they are the same. The end ports are round. Check out this gasket - https://www.carid.com/1968-pontiac-gto-exhaust-systems/mr-gasket-ultra-seal-exhaust-manifold-gasket-set-231314819.html

Here is a picture of the correct 1968 GTO - left side: https://www.partrequest.com/auto-parts-detail/1968-pontiac-lemans-gto-350-left-side-exhaust-manifold-391887962509#

For performance, unless you gotta have original, upgrade to the better Ram Air manifolds.
 

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Discussion Starter #5
Thanks Jim , The manifold is the only part of the engine which does not match, will run with it until I find the correct one.
 
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