How are my main clearances?

[88BB8B]

Hey everybody. I'm sure this sort of thing gets asked a lot, but I was needing the advice of some more experienced people since this is my first time rebuilding one of these. So I'll keep it brief.

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1. 0.0026"
2. 0.00215"
3. 0.0023"
4. 0.0022"
5. 0.0021"

I think they look good for the most part for my goals of 400-450hp. I'm slightly worried about the difference between the 0.0026" and the rest. You guys think it'll run well with 10-40? How could I or should I open up the others a few +0.0001" to match Journal #1?

 

[dustyboner]

standard value
.0008-.0020

limit
.004

so your within the limit but outside the standard valve.

you could mix and match bearing shells if you want to tighten up the clearances a little

if opening them up means you have machining equipment, i guess you could install thicker bearings, measure the ID and grind the crank to match the bearings with the proper oil clearance.

 

[88BB8B]

I know the spec and tolerance limit, and I know I'm okay in that below 0.003" for all which is what a lot of people say is safe for a moderate build. I was just concerned that the relatively large difference between journal #1 and the others might cause issue. So I was considering polishing the crank a few tenths if it would help. Or lightly honing the other 4 journals by hand a few tenths if that wouldn't put things out if alignment. I'm thinking about 0.0025" for each is where I'd like to be, but if more experienced people say I'd probably be better to just run it as is then that's what I'll do.

 

[DSMPT]

I was considering polishing the crank a few tenths if it would help. Or lightly honing the other 4 journals by hand a few tenths

You can have the crank polished by a machine shop to adjust clearances. But no, that's not a good idea to hone the block side by hand by yourself.
Did you measure those numbers by yourself? and did you have the block line-honed and the crank inspected by a machine shop? If you did, I wouldn't be worried too much about those differences. Since you mentioned this is the first time you rebuild, some factors would easily affect a few .0001", like how you torque, how you use the tools, the accuracy of the tools, room temp etc etc. If you would measure again, you may probably see a little different numbers. If you are worried, have those inspected by a machine shop or someone who knows well locally. The best is to set all the same but you can run it like that without any issues in general.

 

[88BB8B]

I measured those numbers myself. I measured the #1 journal like four times to make sure, and that was the smallest consistent measurement I could get. I had the block and crank checked at the machine shop. The main bores were all on size, the #3 had a 0.0005" taper but it looked good otherwise so I opted for no line hone ($250).
The mic I was using gave consistent measurements on the same jourals but I'll measure again when I'm with the motor.

 

[1990TSIAWDTALON]

Run it. Its fine. Don't touch a thing.
My .02 cents
You are worrying about nothing.
Main bearings don't see anything but roational load (and a tad bit of side load with the clutch depressed) so the crank really won't care. It's going to be just fine.

 

[Zack Huffman]

I agree with Marty.

You might try swapping the bearings in 1 and 5 and measuring again, but all of those values should be fine.

 

[88BB8B]

Thanks for chiming in guys. I'll keep it as is then. If my rods have similar differences, would that matter more than the mains? As long as they're all within the 2-3 thou or so range?