crankshaft 63 SHP

[jim cear]

My machinist says that the crank needs to be ground 20 under. Would I be better off/safer with a new replacement or is the regrind acceptable?

[William C.]

Re: crankshaft 63 SHP

There are several threads on this topic in the archives, bu the summary is for anything less that all-out racing, a properly done regrind is perfectly suitable.

[nancy charles]

Re: crankshaft 63 SHP

by cutting the crank .020 under doesn't that weaken it by taking out the tough ride suffice ?

[Dick W.]

Re: crankshaft 63 SHP

Tufftriding I believe came about in the later 60's. A properly ground and radiused crank journal is durable enough for a street engine without any worry.

Years ago, before the advent of all the aftermarket crankshafts, quite a few racing cranks were turned undersize to index the throws. Precision crank machining at the factories left something to be desired.

[nancy charles]

Re: crankshaft 63 SHP

are you saying a 327/340 ( S.H.P. ) crank is the same as a 327/250 ( H.P. ) ?

[Chris D.]

Re: crankshaft 63 SHP

Different part numbers were made from the same raw forging. 340 & 360 HP cranks were drilled and tapped for the harmonic damper bolt. I suspect they were balanced differently as the piston weights were different. Don't know about surface treatments.

[William C.]

Re: crankshaft 63 SHP

Yes, with the exception of balancing and turtriding process. The surface hardening is a nice touch for an engine being raced, but is not really necessary for a street engine, including one that sees an occasional burst of driver exuberance.

[Duke W.]

Re: crankshaft 63 SHP

The first question I would ask is: Why does it need to be ground?

All the journals on my 327/340 crank at 115K miles miced out right in the middle of the OE dimension range. I had it Magnafluxed (passed), checked for straightness (passed), and polished.

These cranks ARE Tufftrided, and it is best not to grind them unless absolutely necessary, however, they will very likely survive in a restored engine, which is not likely to be run at high revs very often.

There are various processes that can restore the surface hardening, but they are usually pretty expensive.

Duke

[Dick W.]

Re: crankshaft 63 SHP

I learned something. I thought that the tufftriding came into being about the time that the 302 engine was built.

[nancy charles]

Re: crankshaft 63 SHP

the 63 340&360 hp. cranks were ( 2680 STEEL )drilled snout for the ( 8" ) balancers .