GM 396 cylinder notches

[ProPower engines]

Hey guys
Is there any way to tell by casting numbers which blocks were really notched for bigger valves.
I am in the process of a build on an early 66 or 67 396 and it does not have notches for s 2.250 valve.
But customer is concerned at this point about a numbers block I am starting with may be not correct.
The block 2 bolt main block casting number is 3855961 if that helps.

Personally I do not find anything in any GM literature about specific blocks that were notched for the bigger valves
Any insight here will be greatly appreciated before I start milling the bores.


Dave

[dannobee]

What is the three letter code on the deck? Is it still there? I'd trust that more (assuming it's still there and not altered) than the casting number.

[SchmidtMotorWorks]

I would be more interested in the chamber match and the measured clearance.

[ProPower engines]

What is the three letter code on the deck? Is it still there? I'd trust that more (assuming it's still there and not altered) than the casting number.

I forgot about that. Too much dodge and ford stuff lately
I will post it tomorrow.

[HDBD]

Often times the casting number does not tell the whole story. For example #512 427 two bolt blocks were used in low HP 69 Impala all the way up to the COPO 425hp 4 bolt blocks with the larger oil pressure outlet and valve reliefs in the cylinders. The machining package for the application and the pad stamp code tells the rest of the story.

[novadude]

I thought the small bore 396 all had notches in the bores.

[F-BIRD'88]

If using 2.25" valves the oem cylinder notch will need radiusing to match.

[BillK]

notches for s 2.250 valve.

Dave,
Dont know how to tell which blocks were notched but I dont think they ever had a 2.250" valve. 2.190" was the largest as far as I know.

[HDBD]

I thought the small bore 396 all had notches in the bores.

I think this is correct.

[F-BIRD'88]

If I wanted to use a 2.25" valve I would swap the 396 block for a 427-454 4.251"++ bore...block The result will be better in EVERY WAY that matters.

[FloydODB]

Just tore apart a 454, 4 bolt 445 casting ckj107443 stamp with notches. RR marine engine.

[rustbucket79]

Were the big valve (375 horse) blocks not all 4 bolt?

[swampbuggy]

I would give a person odds that they were all 4-Bolt main caps, Mark H.

[swampbuggy]

Addendum to the above, "All" meaning ( High Performance ) / highest power rated engines in each cubic inch size examples= 302/290....327/375...350/370...396/375...396/425 only offered in 1965 i do believe...427/435...454/460 . I know that there were other engines with slightly less power that were also 4-Bolt blocks. Mark H.

[HDBD]

They had 4 bolt main caps, yes but the lower horsepower versions, sometimes with the same casting numbers had a smaller oil pressure outlet and 2 bolt mains.