Moz Ray

What is the correct type of Crankshaft for my car (see types below)? According to the 1978 Chevrolet Corvette Chassis & Body Parts Catalog, the part number is 3838495 (ID# 2680). Also, bought a NOS (new-in-the-box) Camshaft (Part# 3863151). Must they be a matching set?

The motor is assembled, but we will disassemble it to install the NOS hi-perf camshaft. Just wondering what to do about the crankshaft that's in there. Thanks.

Cast Crank - the crankshaft is made from cast iron like the block. Determined by the thin, sharp casting seam the length of the crankshaft.
Iron Crank - same as cast crank.
Steel Crank - actually a forged steel crank. Crank is not cast but forged and is stronger than cast. Easily determined by the forging seam that looks like someone ground it with a grinder, where the cast seam is a thin, sharp line. However, this has been counterfeited before so buyer beware.
Forged Crank - A forged steel crank.
Billet Crank - The crankshaft is machined from a single piece of billet steel, not forged, and is much stronger than a forging.

From NCRS.org: "All 62-67 327s used 3.25" stroke, forged crankshafts although there were some differences between finished crankshafts. I'm not aware that any of the small journal, pre-68 327 crankshaft journals were "Tuff-Trided" (Parkerized), although the SHP versions may have been. The primary difference between the non-SHP and SHP cranks was the addition of the balancer retaining bolt tapping. I'll have to check on the "Tuff-Triding" feature.

There were actually several small journal, 327 crankshaft forgings. The one used for non-SHP applications is usually identified by the forging number "3782680". The one used for SHP applications is usually identified by just the derivative "2680". However, I think that there may have been cases in which these forgings were used interchangeably for non-SHP and SHP, particularly involving the use of the "2680" for non-SHP. The 327 non-SHP FINISHED crankshaft was known as GM #3889304 and there was an earlier part number, although both used the same forging. The SHP FINISHED crankshaft was GM #3838495 and there may also have been an earlier part number which used the same forging. FINISHED part numbers do not appear anywhere on a crankshaft, though.

There were also other 2.30" ("small") main journal 327 crankshaft forgings. These included, at least, "3814671", "4577, "3734627", and possibly others."


1965 L79 327 ci/350 hp Hi-Perf with Hydraulic Lifters and A/C

JohnZ

The 2680 forging (Tufftrided) was originally used for your application; Tufftriding was a chemical heat-treating process that produced a hardened case depth of about .010". That said, any small-journal forged 327 crank will work fine.

The "151" cam is correct for your application; use new lifters and stock springs (GM #3911068 or Federal-Mogul #VS-677).

Moz Ray

Thanks much John.

Take care,
Moshe