Howdy, Gentlemen,

I have a tired three-plug short block I wish to build for my HAMBster's next season.

Its crank, in addition to being cut .010" under on all journals, has had large balance holes bored too deeply into the throw arm ends (right beside the rod journals) on #1 and #6, compromising the support there.
I won't use this crank, I've seen that sort of failure before.

I'm thinking of replacing it with as late a forged crank as I can find, and am researching the viability of the cobble.
As I see it, a later crank should have a bit lighter counterweights, with shallower balance holes there, and thus stronger there.

I have a lathe, so the flywheel register size difference isn't a problem.
Are there any other reasons this wouldn't be a drop-in? Oil passage differences? Thrust bearing changes? You get the idea.

_________________
Sex, drags, and rock & roll.
Dick, 225% crazy.
Hobby (cars, that is) Photos link

I am running a 1976 forged crank in a 1963 block...make sure that you check the journals for wear and get the correct bearings and it should be a drop in if everything checks out.

All forged cranks interchange, so no troubles. 1976 crank should weigh less and be stone reliable. If I were building it, I would turn it for best bearing surfaces and balance it. Rods and pistons should also be balanced (with each other, no reason to balance with crank for an inline 6 engine).

Best,

Lou

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Home of Slant6-powered fun machines since 1988

Thank you. Pretty much what my attempts at homework'd hinted at, and what I was hoping to hear.

My final conclusion of how my last crank failed is from a torsional break at the #6 journal's junction with its rear throw arm, with the rest of the "car"nage following from that start.

I believe this to've been initiated by the seperation of #6 slug's top, and subsequent jamming against the returning rod. The drive train, still turning, likely aided and abetted that initial surgery.
Still, I won't be reducing the journals, weakening that junction.

Here's the ad I'm posting in the "Wanted" area, for said crank.

_________________
Sex, drags, and rock & roll.
Dick, 225% crazy.
Hobby (cars, that is) Photos link