scored crankshaft

[Mike Sasser]

I took my 65 327, 300 hp engine apart and found a badly scored crankshaft, both rod journals and mains. The problem is that it is already 20 under. Do you think it is OK to grind to 30 under or should I look for another crankshaft. Also the first two journals has excesive rod side clearance, the first journal is .02 over and the second is .04 over clearance. What should be done about that? Thanks for the help

[Gerry Proctor]

Re: scored crankshaft

The crank could go .030 under, but your real problem is the side clearance. Considering that 3.25-stroke cranks aren't rare, there is no economically feasible solution to closing up the side clearance if the problem is in the crank. Generally, the crank would need to be welded but this is only a realistic option for rare cranks (like steel 427 Ford cranks). Are you sure that it's not in the rods? If it's the rods, you grind the crank and replace the rods.

[Dale Pearman]

Re: scored crankshaft

You can replace the crankshaft for about $150.00 with a used original unturned. They are plentiful. Polishing the journals is very inexpensive at most machine shops.

I wouldn't be too concerned about excessive rod clearance if you choose to use your old crank. That just means more oil for the camshaft.

Dale.

[Mike Sasser]

more questions, scored crankshaft

I took two rods from the other end of the engine where the rod side clearance is good and placed them on the first journal and the clearance was out of speck, this would seem to tell me it is the crank that is bad. If I get another crank would any crank out of a 60's era 327 engine work? The crank is stamped 2680, is that the number I look for on a replacement? Thanks for your help

[Joe L.]

Re: more questions, scored crankshaft

Mike-----

Well, MOST, but not ALL, 60's era 327 crankshafts will work. However, late 60s will not since, in 1968, Chevrolet went to larger main journal size on 327 cranks. So, you need a 62-67 327 crankshaft. All of these are forged steel, too, whereas later 327 cranks are usually cast iron (except 68 L-79 which is forged steel and large journal).

Forging number "2680" is a common one to look for. Others include "4577", "3884577" and "3782680" (usually this last one is NOT drilled and tapped for a balancer bolt, though).

[Dale Pearman]

Re: more questions, scored crankshaft

1962 steel crankshafts, both drilled and undrilled, are readily available at $150.00 each. Most have NEVER been turned. They are 2680 cranks.

Cast cranks with identical journal sizes as the 2680s are also available wikth 1962 dates and offer certain advantages in show cars as well as street driven Corvettes.

Dale.

[Joe L.]

Re: more questions, scored crankshaft

Dale-----

Really? What are the casting numbers of these early, small journal CAST 327 crankshafts? I've never seen one or heard of one.

[Dale Pearman]

Re: more questions, scored crankshaft

I peek at a couple in my shop tomorrow and e-mail you.

Regards,

Dale.

[Mike Sasser]

Thanks! *NM*