Quote:
Originally Posted by special-K
...But the 326 uses the same block as the 455. I'd want people to think my '67 had a 389 but would likely wind up with a more common displacement dressed to appear as one.
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Spot on Special-K,
Should you go with a Pontiac in your GMC...the 400 block is the most available AND is the most popular to stroke. Modern forged crank designs allow for that 400 to be reliably stroked to tremendous cubes while keeping the smaller crank journals (compared to the larger journals of the 455)...this equals an engine with high output, modern crank strength, and higher available RPM's. This approach (stroked or not) can look almost exactly like a 389, excepting casting numbers.
It's a very common thought that Pontiacs are big blocks since the 455 "sounds" like a big block and the 389 & 400 are the same block casting. The 326 usually falsely carries the small block stigma, but, as mentioned, is the same casting too. The kicker is that they are all designed more like a big block for durability when compared to other GM small blocks of similar bore and stroke. I believe there are differences between the 326, 389, 400, 421, 428, & 455 blocks. They are the same external dimensions, but the inner wall casting thickness can vary from size to size depending on the cylinder bore.
I'm not picking sides here, just glad to throw some Pontiac info out and glad to join a ToTM!