GM 396 cylinder notches

[dondon]

they never made a 327 4 bolt. you could make one 1968 up 327 large journal.

[midnightbluS10]

they never made a 327 4 bolt. you could make one 1968 up 327 large journal.

Supposedly, they came in Massey Ferguson combines. That's the explanation I've seen multiple times. It would explain why there's no documentation of one in GM cars & trucks. I realize that's a convenient explanation but who says it's not true? It very well could be.

[Ericnova]

they never made a 327 4 bolt. you could make one 1968 up 327 large journal.

Supposedly, they came in Massey Ferguson combines. That's the explanation I've seen multiple times. It would explain why there's no documentation of one in GM cars & trucks. I realize that's a convenient explanation but who says it's not true? It very well could be.

I've seen one of those, roughly 20 years ago, in a buddy's possession just hours after pulling it out of the combine.
Appeared to be basically a 300 Hp 327....1.94" valve camel humps and flat top pistons with just a couple durability upgrades which were oil pump and factory double roller timing chain.
I didn't get to see the cam, just hydro flat tappet, but I wouldn't expect much beyond just stock -929 or similar.

but sorry, it was 2-bolt mains, small journal forged crank, 90+ lb flywheel(LOL)

[ProPower engines]

Just an FYI on the block,
Its a truck block. It had no int. valve reliefs in the bores but customer came up with a different block with the
valve notch's and its numbers matching for his Chevelle so it worked out in the end.
It also is a 2 bolt block but I am going to put steel caps on it anyway so no issue with strength when dropping the clutch.


Thanks to those that posted here gave me some stuff to look for in other areas.

[swampbuggy]

I learned something i was not aware of ( the earlier 327 hi-Horsepower engines were 2-Bolt Main Caps) and that is good that i learned. I never have tried to hold a doctorate degree in knowledge on OEM data, but i definitely admire those who do ! . So with all the thrashing on the street and drag strips of the 2-Bolt 327's it causes me to think how many failures were linked directly to 2-Bolt main cap blocks ??? Anybody ? Mark H.

[Old School]

I learned something i was not aware of ( the earlier 327 hi-Horsepower engines were 2-Bolt Main Caps) and that is good that i learned. I never have tried to hold a doctorate degree in knowledge on OEM data, but i definitely admire those who do ! . So with all the thrashing on the street and drag strips of the 2-Bolt 327's it causes me to think how many failures were linked directly to 2-Bolt main cap blocks ??? Anybody ? Mark H.

Not as many failures linked to the 2 bolts as to the lack of knowledge and tools. No one had tools or the knowledge to set bearing clearances. Ignorance about piston/valve clearance, guide to retainer, all the things we check as standard assembly today. Everyone was learning with very few resources. Today one can to to a big bracket race and see a couple thousand runs a weekend and not one engine lost. Back in the 60's that wasn't the case and it happened with all brands of engines. A top of the line 327 50 years ago was lucky to make 450 horsepower. Most were about 350 for the average racer.

[MotionMachine]

Who else has seen a 305 4 bolt block? Had I not seen it myself I would not have believed it. Best we could determine, it came out of a school bus in Canada.

[rustbucket79]

I’ve seen probably 50 305 blocks in my career and never once a 4 bolt. (I’m Canadian)

More likely a goof up at the GM factory. If I had worked there “back in the day” I’d try and sneak a 305 or 307 block into the 4 bolt line just for shits and giggles.

[dannobee]

Weren't the 4 bolt 305 blocks only Canadian 3/4 ton pickups and only for two years?

No 4 bolt main small journal small blocks though.

In circle track racing I've personally had a few 4 bolt blocks rip apart the main webbing at about the 600hp level. Not pretty. I think the factory way of installing the outer two bolts contribute to the weakness. Especially over the splayed cap layout.