crank #'s

[Stephen W.]

Need Joe's help with some numbers.

Crankshaft for 1968 327 with following numbers. 3911001

Would this be the correct crank for my 327/350 engine?

[John H.]

Re: crank #'s

Steve -

Nope, that's a large-journal cast crank; you need a small-journal forged crank, assuming you have the correct small-journal block.

[Andy #28359]

Re: crank #'s

'68 327's HAVE large-journal cranks/blocks.

[Joe L.]

Re: crank #'s

Andy, Steve, and John-----

Yes, 1968 327 cid engines for all applicayions did use the large journal crank. It was the first and only use of a large journal crank in a Corvette 327. As John mentioned, the GM casting #3911001 is a cast nodular iron crank of large journal size. With custom balancing of the reciprocating assembly, it will work for Steve's application, but it's not the correct crankshaft. The correct one is GM forging #3914672. This is one of the most difficult of all Chevrolet crankshafts to find. It was originally used ONLY for 1968 Corvette L-79, 1968 Chevelle L-79, and some 1968 HD truck applications.

By the way, with custom balancing, the 3911001 crankshaft will work just fine for a 1968 L-79 application. Nodular iron crankshafts in small blocks are good up to, at least, 500 hp. There's no way a 1968 Corvette L-79 is going to generate more power than that.

[Stephen W.]

Re: crank #'s

The car is a late production car. Mid July production date but I'm not sure about the engine assembly date. Pad shows numbers match and 327/350 MT.

[John H.]

Re: crank #'s

Oops! Missed the "'68" in the original post - have '67 on the brain

[Stephen W.]

Re: crank #'s

Thanks Joe!
The original rods are available for this crank as well so it looks like balancing the assembly will not be a problem.
Thanks to everyone for the help!

[Joe L.]

Re: crank #'s

Steve------

The original rods used for the 1968 L-79 were the same forging as those used for other 1968 307 and 327 engines with nodular iron cranks. The only difference was the finishing of the rod (i.e. shot peening, magnaflux, etc.). So, as far as rod weight goes, it should be just about the same for any 1968 large journal rod. Plus, you can use any 69+ 350 rod, too.

Another option: use current GM powder metal rods. These are far stronger than any original conventional forged rod AND they are available at a very economical price. A set is sold under GM #12495071. The set carries a GM list price of $307.68 and can be purchased for about $250.

Another option: convert the engine to a 350 cid. All you need is a forged (or, cast) 350 crank. These are easy to come by, although the forged version is not inexpensive. However, both are available new from GM. They'll bolt right in. The same rods can be used, either original or the ones I mentioned above. The only other difference will be the pistons---use the 350 pistons of your choice. You'll need to change the harmonic balancer, too. When you're done, you'll have more power and torque and, externally, the engine will be virtually indistinguishable from the original 327. The only visible "cue" that it's been upgraded to 350 engine size? The timing mark and tab. VERY few will figure this one out, especially if you use an original 350 timing cover with welded-on tab.