How do you confirm original 396 motor parts?

[Ken Seddon - 25329]

Hello all! I've been through the judging manual and I have a few parts that I am trying to figure out if they are original 396 parts or not. If they are not, do they need to be correct for judging purposes.

1) How do you identify original pistons?
2) How do you identify an original harmonic balancer?
3) what is a high volume o/c pump and what's the correct part number?

Thanks,
Ken

[Joe L.]

Re: How do you confirm original 396 motor parts?

Ken-----

The pistons and oil pump do not need to be correct for judging purposes. At least, they don't until judges with x-ray vision get into the act. In any event, the pistons were forged, domed style pistons. The unique 396 bore size of 4.094" is one thing to check and these pistons should weigh right at 24 oz. There may or may not be a forging number on the underside of the pistons. If there is, it should be a number beginning with "386" or "387". I don't know what the exact forging number was. Also, many of these early forged pistons may have "TRW" on the bottom and/or "GM". TRW manufactured the forged blanks for GM, although I believe that the pistons were machined and finished at the GM engine plants.

The 1965 L-78 oil pump was GM #3876868, but this number will be found nowhere on the pump. It was discontinued years ago and replaced by several supercessive part numbers which are no longer available from GM, either. The cover on this pump will be cast 3860376, but this cover casting was also used for other big block pumps. This pump was a "high pressure" pump but it was NOT a "high volume" pump. The only high volume pump ever used in PRODUCTION for any big block engine (or, for that matter, on ANY PRODUCTION Chevrolet V-8 engine) was the ZL-1 pump. The pressure relief spring in the 65 L-78 pump will have 24 coils, a free length of 2-7/16", and an OD of 5/16". An identifying stripe of light green dye may or may not be visible.

The harmonic balancer used for the 1965 L-78 was of GM #3860010. This is a "3 spoke", 8" balancer of 1-11/16" thickness. It was used on most other 65-69 SHP big blocks except L-88/ZL-1. It MAY have the number "0010" stamped on it, or it may not.

[Bill W.]

Re: How do you confirm original 396 motor parts?

The pistons from 16120 are marked ...GM 456 TRW...a "B" under the 456 & upside down # 3856250..If the engine is from # 17346 I want it back . Bill