Memory check

[Michael H.]

Cross Drilled SB Crankshaft ?

I don't think I agree with Mr Colvins theory that tuftriding began in 1964. All of the high perf crankshafts for 63-67 were "induction hardened", not tuftried. Induction hardening is a totally different process. Also, I'd like to learn more about 64 crankshafts being cross drilled.

I remember one new short block in the crate that the "S" but it was backwards, the mirror image of an S.

[Mike McKown]

I don't agree either.

It's just what he put in his book.

[Clem Z.]

Re: Cross Drilled SB Crankshaft ?

BBC cranks were crossed drilled but not SBC cranks.since the 65 BBC were started to be built in 64 maybe that is where this came from. we always ground a "lead in trough" on SBC cranks to make sure the oil got a head start before the hole in the mains got to the groove in the upper main bearing shell.

[Michael H.]

Re: Cross Drilled SB Crankshaft ?

Yes, I've never heard of a factory cross drilled small block crankshaft. I don't think there is any such thing. In fact, the only big block cross drilled units were those used for L88/Zl1. (maybe also the 71 LS?) Is this info really in the Colvin book?

[Clem Z.]

Re: Cross Drilled SB Crankshaft ?

all solid lifter BBC engine had crossed drilled cranks starting in 1965. the hyd lifter ones did not. never saw the book

[Mike McKown]

Re: Cross Drilled SB Crankshaft ?

Well, If I didn't forget what I read before I got to the house after I left the garage where my reading material is, that's what I remember it said. I'll double check and post.

(Just a dumb hillbilly searching for the truth)

[Mike McKown]

A few excerpts from AC

Chevrolet by the numbers 1960-64 on the crank intro page.

"Another distinguishing feature between crankshafts is the result of a special treatment called Tuftriding. From all indications, this treatment began in the 1964 model year on Corvette 327/365 and 375 HP crankshafts. The treatment involved a chemical heat-treating process that hardened the rod and main journal surfaces of most forged steel crankshafts to be used in high performance applications. Tuftrided crankshafts have a dull gray finish".

"Many small block crankshafts, including truck and all high performance applications, also have cross drilled main bearing journals........... All Tuftrided crankshafts have been cross drilled but not all cross drilled cranks have been Tuftrided"

Chevrolet by the numbers 1965-69:

Says the same thing but not exactly verbatim.

Corvette by the numbers 1955-82:

Same as above.

Looking a little closer, he has the rod jounal diameter screwed up in the Corvette book. He lists the 327 journal as 2.10/2.20. In the pass car book he has it right. 2.0

Still, he does show different forge numbers between HP and SHP. Also indicated is a different forging number for "66-'67. Why would forging numbers be different?

Mike: For what it's worth, I have a 327 crank forged 4577 that has a dull gray finish just like my '67 302 crank. I know MOST 327 cranks have a very shiny, as machined surface. Do you think it possible the '62-'63 cranks were hardened by one process and '64-65 by another?

No big deal here. Some people go crazy over "correct" bolt heads. I like engine parts.

[Mike McKown]

Chevrolet Power Book 1975,1978

"All production 302 and heavy duty 327 and 350 crankshafts are "Tufftride" heat treated to improve journal hardness and give greater fatigue strength for high performance durability. This feature is an improvement to any high performance forged crnakshaft and should be in included in any engine build performance crankshaft and should be included in any engine build".

So, if taken from the horses' mouth, all 327 SHP cranks have been Tufftrided?

I'm still curious about the blue paint swatches.

I think they were on the block ( Which Mike verified), the crank flywheel flange, connecting rods, and valve springs. I keep hearing on this forum that the solid lifter springs were the same as regular production and I don't agree with this. The replacement nowadays may be so. Not back then.

[John H.]

Re: Chevrolet Power Book 1975,1978

Mike -

The production small-block solid lifter springs had the same closed and open pressures (85# and 195#-200#) as the grocery-getter hydraulic-lifter springs, but had a different heat-treat for durability, thus different part numbers.

There was an over-the-counter "Z/28 Heavy-Duty" spring (#3927142) that was designed for use with the "-140" First-Design Off-Road cam with higher pressures and was about .030" larger in O.D. and was painted brown, but it was never used in a production engine; it was created as the SCCA-legal GM spring for the Trans-Am Camaros.

[Mike McKown]

Re: Chevrolet Power Book 1975,1978

I agree on the 327 springs and the heat treat. I believe they also had a paint swatch ID to differentiate them from the grocery getters.