what do you think of my bearing clearances?

[slimtastic]

well long story short, im going though my motor that i got back from the high perf. shop that did a "less than good job" and i changed the main bearings to federal mogul 3/4 groove bearings ive got the clearances as follows. what are your opinions?
main 1 .0020
main 2 .0018
main 3 .0017
main 4 .0021

the rods have me concerned though. i measured the crank pins and pin 3 and 4 are a little larger than the rest( this crank is 20/10 cut). so my clearances are as follows.
rod 1 .0020
rod 2 .0019
rod 3 .0015 *
rod 4 .0016 *
rod 5 .0020
rod 6 .0019
my concern is that the clearances on 3 and 4 will be too tight but i wanted to check. the plan for this motor is easy tens and the rpms under 6100 at all times. my question is that if im not reving the motor super high, can i run a tighter rod bearing? ive always had it in my head that a loose bearing is for motors that need to have BIG rpm to make power. what do ya'll think?

 

[bison]

They look ok. The .0015 on the rods is not a problem. I like them closer to .002 myself but they are still ok. I wouldnt be so concerned with them a little tighter than .002. If the mains go much over .002 you may have some problems. Im suprised the clearances have that much variance. Must have been a lazy crank grinder on that one.

 

[750H.P.V6]

There is a bit of variance in those clearances across the board but I don't see anything that is going to cause a major problem. I'd be upset if I'd paid a lot of money to get that quality of machine work but with that said I think you're OK.

Neal

 

[DonnieShort]

When I did my motor last year, I had my mains set .002 on 1,2,3 and it was at .0022 on the 4th. I used billit main caps on 1-3 and reused the stock main on 4 thus the slight difference. On the rods I went with .002 on all of them, my crank is stock and standard.

Haven't had a minutes problem, great oil pressure. 30psi when warm and 60psi at cruise. When you stand on it at wot it's at 70psi.

 

[slimtastic]

thanks guys. im running the wide clevite 77's for the rod bearings. id like to buy two federal mogul wide rod bearings to see if the bearing clearance will change (see if i cant get that .0004 back). but if it wont work ill run the clearances it has now.

 

[turbodave231]

Beg borrow or steal some good measuring equipment.

Use a micrometer and measure your journal diameters, then Put your main caps on without bearings and torque them to specs. Measure your line bore (telescoping gauges or dial bore gauge)to be sure all 4 holes are round and the same size. Do the same with your rods.

Perhaps your machinist wasn't paying attention when he reconed your rods or did the line bore. That would account for the big variance in rod clearances.

Measure, that is the only way to know where the problem is...

Dave

 

[NC87GN]

Your fine with those clearances.. Smooth out all the sharp radii in the front cover and match port all your passages.

Mike Banas
87GN

 

[bison]

Beg borrow or steal some good measuring equipment.

Use a micrometer and measure your journal diameters, then Put your main caps on without bearings and torque them to specs. Measure your line bore (telescoping gauges or dial bore gauge)to be sure all 4 holes are round and the same size. Do the same with your rods.

Perhaps your machinist wasn't paying attention when he reconed your rods or did the line bore. That would account for the big variance in rod clearances.

Measure, that is the only way to know where the problem is...

Dave

Probably the crank grinder was just a lazy a$$ and didnt care if he was off a few tenths.