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Yoda
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I do a certain portion of amchine work in house, most of all the head work, and rod work, I do out source boroing, line boring, and crnakshaft grinding. The crankshaft grinder I use, Spartan Crankshaft is one of the best I ever seen, I've been using them for close to 20 years, all they do is crankshafts, and they know how to do them right. Crankshaft grinding is a art form as foar as I'm concerned, I could let the same machinist that does my broing and line boring do my crnaks, but the bottom line is he maybe does 2-3 crnaks a month, where Spartan does dozen fo crank weekly, so you can fiquire out real quick who will do the better job. I blueprint everything I built, so I tell the crnak grinder what number I wont them to hit, so I get the exact clearence I want, a good grinder will hit your numbers by +/- .0002", my guys seldomly ever are as much as .0002" off, normally within .0001, that in short is outstanding work. Another big deal about crnak grinding putting the fliet radius on the edge of the journals back, and this is where alot of 'so called" crank grinders suck, they square off the radius, or they don't want to dress their grinding wheels so they make a few steps at the end to sorta create a radius. When the radius is not put back properly this cause a stress riser, most all cracks in crnakshaft happen at the radius on the journals, the better the radius is the less chance a crank will crack there.
Ray sourced a 1275 engine core form a buddy of mine, none of us knew any history about Ray's core. When I got the core apart, the bores were still standard. but someone had ground the crank .010/.010, and the radiuses looked terrible, and I just didn't want to take Ray's motor to a .020/.020 crnak, so I had a nice std/std crank in my stash and we used that. Well we got my lathe repaired the other day, and was looking for something to do to try it out, so the crank that originally came out of Ray's core engine was used for a polish job to give the lathe a try out. Once I polished the journal up, I saw what I thought was couple of scratches on the #4 rod journal, closer inspection proved they were cracks not scratches, one coming form the radius, about 3/8", and the ohter came off the same radius at a angle of about 3/4" (biggest crack I ever saw in a crank. The mroal to all this was, whoever ground this crnakshaft originally was a lazy "you know what", he stepped the radius and for all prectical purposes wiped it away, and this shotty job caused this crnakshaft to crack, and it's a wonder it dodn't break in the block while the engine was still running.
The moral of all this is to find out in your area who does the good crank work, where do the racers take thier cranks, and that's who you want grinding your crank. Don't think just because a machiinst has a crank grinder and does crank grinding he can actually do a good job of it. A good question for a machinist who grinds cranks is to ask them how they do their radiuses on the journal, if you get a bunch of hee-hawing, then run
Sidenote, only twice have I ever sourced a already ground crankshaft from British parts vendors who use what ever shop is near them mostly to do the machine work, both big names in the business, I used neither of these cranks as they were sent to me (crappy radiuses, and journal sizes all over the place) both were re-done by my guys.
Ray sourced a 1275 engine core form a buddy of mine, none of us knew any history about Ray's core. When I got the core apart, the bores were still standard. but someone had ground the crank .010/.010, and the radiuses looked terrible, and I just didn't want to take Ray's motor to a .020/.020 crnak, so I had a nice std/std crank in my stash and we used that. Well we got my lathe repaired the other day, and was looking for something to do to try it out, so the crank that originally came out of Ray's core engine was used for a polish job to give the lathe a try out. Once I polished the journal up, I saw what I thought was couple of scratches on the #4 rod journal, closer inspection proved they were cracks not scratches, one coming form the radius, about 3/8", and the ohter came off the same radius at a angle of about 3/4" (biggest crack I ever saw in a crank. The mroal to all this was, whoever ground this crnakshaft originally was a lazy "you know what", he stepped the radius and for all prectical purposes wiped it away, and this shotty job caused this crnakshaft to crack, and it's a wonder it dodn't break in the block while the engine was still running.
The moral of all this is to find out in your area who does the good crank work, where do the racers take thier cranks, and that's who you want grinding your crank. Don't think just because a machiinst has a crank grinder and does crank grinding he can actually do a good job of it. A good question for a machinist who grinds cranks is to ask them how they do their radiuses on the journal, if you get a bunch of hee-hawing, then run
Sidenote, only twice have I ever sourced a already ground crankshaft from British parts vendors who use what ever shop is near them mostly to do the machine work, both big names in the business, I used neither of these cranks as they were sent to me (crappy radiuses, and journal sizes all over the place) both were re-done by my guys.
