Quote:
Originally Posted by alchemy
A question about shot peening: Do you guys (engine machinists) think that shot peening roughs up the bearings surfaces enough that they need to be honed smooth again. A friend who is a retired machinist (industrial, not engine shop) says that the grit will raise the surface of the block, and cause the tolerances to close up so the main bearings, cam bearings, and lifters will not fit correctly. He likes to run a hone through all those openings to knock down the surfaces. What do you guys think and do?
I suggested we just leave the old bearings in the block when we have it blasted, but that still doesn't protect the lifter bosses.
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The last auto machine shop I ran for 10yr's before I retired we bought a baking oven and shot peen setup. $35000.00. A lot of blocks went through there in 10yr's. I've been retired 15yr's and still build 10-12 engine every year mostly in the winter. Every one is baked and peened. I always run a blueberry hone ( like the one you hone break cyl, with) through the lifter bores and guide bores. The steel shot will bugger the sharp edge on the lifter bore and make the lifters and guides go in hard. Then I spray it down with WD-40 or oil and finish boring cyl and grinding valve seats. Then run the engine through a jet washer, then it's spotless and ready to build. I've never seen any damage to main bearing bore or cam bearing bore. Walt