I have just been around and around with two machine shops trying to insure that my re-worked crank and rods have the correct side play. All except the one journal that had spun a bearing check within the spec's of .063 to .0118 (max) as listed in the Chilton manual for this engine, however, the one which spun which is getting a new rod measures about .016. Several mechanics and both machine shops say this is not an issue to worry about. One even claims many racers are running as much as .080 is many different engines, so... the question is, does the extra side play matter, and if so, why? Seems to me there would not be a max limit listed if there were not a problem being in excess of it. What do you guys and ladies think?
Rod big end side clearance?
- Thread starter rustfarmer
- Start date
Really? I thought that oil pressure was mostly a function of rod bearing clearance, not side play. More info or references would be greatly appreciated.
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And I wouldn't trust a Chilton manual except to clean up dog pee in the garage.
Look it up in the TSRM.
Look it up in the TSRM.
Fair enough, you are correct that the chilton books suck. If I can't get the correct side play by using a different rod, guess I'll have to fight with the crank grinder. Is there any reason not to weld up this journal and re-cut it? I do have the 7M-GE that I pulled from the car with a BHG and 200K miles, so I guess I could use that crank and have it worked, but that would mean different bearings but might not have to cut it as much. Current crank was cut .030 rods, .010 mains. If I can't get the crank grinder to re-do his sloppy work free, guess I'll change shops and call it a learning experience. Anyway, thanks for you input.
Don't quote me on this but research has told me that anything more than .010" cut on the 6m/7m crank will go past the heat treating on the journals and sacrifice strength of the journal. There's no reason to weld a 6m/7m crank for the reason that simply getting another good crank is not difficult or expensive, and is going to be a better piece in the end.
Find another crank. The side clearance on the rods isnt very much.
A few of motors Ive done had too much play and was the crank, rods checked good
A few of motors Ive done had too much play and was the crank, rods checked good
Yea, that's my deal as the journal with too much play was the one that spun a bearing. What chaps my butt is that I payed $150 to a "race" machine shop to turn this crank and they claim the extra clearance doesn't matter, and that if it wasn't OK to cut the rod journals .030 they would not offer bearing in this oversize. Anyway, I do have another crank that is likely much better. Haven't pulled that crank out of block yet.
Thanks to all responders. I pulled the crank fro the old 7M-GE that came with this car (BHG) and had my regular machine shop check it. For $32 they polished all stock size journals and said it spec's out perfect. Much more confident now that I will be building a solid bottom end.