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By Duck - 17 Years Ago
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Fellas- when having a 312 crank machined to be used in a 292 block, does the rear main seal surface need to be machined as well as the main journals? If so, to what dimension will it need to be turned to? Thank you,- Duck-
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By Hoosier Hurricane - 17 Years Ago
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Yes, it needs to be machined to 292 size, then a 292 seal fits properly. The problem is finding a crank grinding shop that has a wheel narrow enough to grind the seal area. The slinger really should be maintained, but ground to 292 diameter so it will fit in the groove in the block. Most grinders will grind that area if they can remove the slinger. That way they can use their standard wide wheel to do it. I believe the seal diameter is 3 5/8, but don't know the diameter of the slinger. I can measure one on a 292 crank if you need me to. John in Selma, IN
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By Duck - 17 Years Ago
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Thank you John- This is the first Y-block I've ever attempted to rebuild- I hope you fellas can bear my ignorance. Unfortunately there's not too many machine shops around here, and fewer still with Y-block experience. I really need to have my ducks in a row when specifying what needs to be accomplished (and not) before turning over this crank for machining. I suppose knowing that the main journals/ rear seal area will need to be to 292 specs is a pretty good start- Thank You T.R.M. /Duck
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By bird55 - 17 Years Ago
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Does this help?
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By Duck - 17 Years Ago
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That works! The printer even has ink right now- Thank You!
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By Ted - 17 Years Ago
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The shop I was using for crankshaft rear seal work had the narrow stone up until about a year ago. When their narrow stone broke, they decided not to replace it and as a result, I’ve ended up not retaining the slinger on the modified 312 crankshafts from that point on. If I had my druthers, I’d rather have the slinger but I haven’t had any leakage issues while using the neoprene rear seals. Like Al’s diagram says, the early cranks did not have the slinger and I haven’t had any issues with those crankshafts either with the neoprene rear seals in place. The only thing I'm doing different is having the rear seal surface on the 312 cranksahfts machined to 2.625" rather than 2.620" for a tad bit more pressure on the rear seal.
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By marvh - 17 Years Ago
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I did some checking awhile back for a source and found there is shop in Whittier, CA 90604 that can do that work.
I have never had a crank done by him however, I have bought ECZ rods with ARP bolts, shot peened and polished from him. Very good machine shop work.
marv
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By PF Arcand - 17 Years Ago
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Just a question on this subject. If by chance you had a 312 seal holder, couldn't you just install it with the 312 seal, avoiding turning down the seal surface?
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By 46yblock - 17 Years Ago
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I was lucky I guess with the 312 crank I had turned down. I told the machine shop that I wanted the ring retained. The shop he sends it to said they didnt have a narrow stone. After crank arrived at the grinder, the grinding shop discovered they did have a narrow stone and ended up saving the ring. The shop is in Eugene, OR.
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By Hoosier Hurricane - 17 Years Ago
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Paul: The 312 seal holder would fit on the block, but the groove in the block for the top half of the seal is too small for the 312 seal. On my engine, I turned the seal area down in a lathe and polished it. John
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