Crankshaft tolerances... Profressional Help only please.

[kutta]

So Here is my Situation. I received a 6 bolt engine that was running fine and decided to pull it apart before installing. Noticed that their were some scratches on the crank so I had it polished. By the time I got it back I noticed that the main bearings were .01 inches (.25mm) , (undersized or over sized) and the rod bearings are .02 inches (.5mm) as well. So My question is in regarded to weither or not I'm going to be ok with my specs.

So Standard specs are for main 2.2433- 2.2439 inches. And for rod bearings it is 1.7709-1.7715. So Since the crank is using oversized bearings I just subtracted .01 from the main tolerances and .02 from the rod tolerances to get this....

Main tolerances for .01 (.25mm) bearings = 2.2333-2.2339

Rod bearing tolerances for .02(.5mm) bearings= 1.7509-1.7515

So out of round slack is 6/tenths (.0006)

So After the crank was polished heard are my measurements stated below

I took two measurements for each
Main

m1 2.2333/ 2.2330

m2 2.2333/ 2.2335

m3 2.2333

m4 2.2335

m5 2.2335


So the lower tolerances for the oversized bearings was 2.2333 and on one of them I'm .0003 off.


Then for the rods I have

r1 1.7505/ 1.7502

r2 1.7505/1.7505

r3 1.7505/ 1.7505

r4 1.7504/ 1.7510

and the Tolerances for the crank for the rods for .02(.5mm) oversized was
1.7509-1.7515 inches.

So as you can see for the rods I'm .0004 -.0007 on one and .0004 on the other. and .0005 on one... Is this going to be ok????

So This sucks because for the ACL tri metal bearings they dont make a .5mm for the rods that I'm aware of. So I have to go with the aluminum ones.. If these tolerances are going to be ok should I run all aluminum or do trimetal ACL for the main and the aluminums for the rods. My goals for this car are going to be a solid daily driver with 350 to 425 HP max as I have a Forced performance 68hta Sitting in My house waiting to be used and some 272/272 cams and other fun stuff. Thanks for the help guys. I know Some people are not as picky about this stuff but I dont care for fast cars that run for only a season. Thanks for the Help

 

[Mechman518]

OK, first question I have is, what did you measure with? Has it been calibrated lately?
If your caliper is off your measurements will be skewed. Be sure your caliper is spot on and retake the measurements.
If the caliper is OK, then I think the mains will be fine with the current tolerances, just use the .01 oversized bearings. As for the rods, if you plan on running SAE 10W40 I'm sure they will also be ok; however, if you plan on running SAE 5W30 then you will want to find something closer to the tolerances of the crankshaft. If all you can find is aluminum bearings then use them. Personally I don't care for aluminum bearings; I like the ACL tri-metal, that's what I run in my engine.
With that said, if it were me I would buy ACL tri-metal bearings for the crank in .01 oversize and for the rod I would run .02 oversize bearings. The tolerances are close enough it will not matter. .0004 inches is equivalent to 10.16 microns, something your engine oil will compensate for.

 

[kutta]

Ok glad someone chimed in. Seems like everyone is sleeping today.

 

[Mechman518]

Questions like this one tend to scare people.