Hi, new member here - We just started a new business after several years acquiring NOS classic parts. I need some help Identifying a 455 block. I am 99% sure this is a NOS block, but the crate was missing. It was stored with 11 other classic NOS blocks I purchased that are still in the GM crates. The casting number is 396021F which should make it a 1970-1972 455. The VIN Derivative Stamp has 1SB above the number 2086. I am wondering if this is a service replacement block. It is a partial block with casting # 39736 on the crankshaft and I can see 398666 on one of the pistons. Also, confusing is the date code appears to be an 8 over 178, which I think means 178th day of 1974? Any information would be greatly appreciated.

 

you have a pm.
Thanks

 

Hi, welcome to the site.

I'm wondering if the "8" you see could possibly be a "6"? 396021F blocks cover the 68-76 era to my understanding. Alluding to it being a 1976 version.

 

Thanks Don71, yes, definitely an 8. I attached pictures - hopefully they post okay.

 

If you take off the timing gear and look at the end of the camshaft, it might have identifying cuts at the perimeter to help identify it and thus the year range of the short block. Also, iirc, around 1972 the factory quit putting spit holes in the connecting rods at the parting line. Around 1970 the chamferred recess in the crank at the flywheel end got noticeably deeper.

 

Whether or not the "F" in the 396021F casting number has serifs or is sans serif can be used to determine whether this is an early or later 455 block. I'll let someone with better knowledge of this than I make the determination.

The "8" cast back by the date code and distributor hole is a mold number. As a very broad generalization, this number incremented each year, with 1968 being the first year for the 455. Thus, an 8 may indeed indicated this block was from 1976. However, this is not set in stone. There are cars out there with original engines which don't have the mold number you might expect.

 

Serif is usually 1970-newer. Sans serif was 68-69.