Reconditioned 37 rods

[Ol' Ron]

Ya gota work with the math, The diameter of the crank subtracted from the bore of the rod and tne thickness of the bearing times two, If the numbers add up and the clearance is right. THEN start fitting them. Also you must check for width , especially in the filit radius of the crank. You don;t want to hang up there. I like .015 on the width of the bearing, this lets the oil out of the bearing. Next the rod side clearance should be .008-.010" on a street engine and .015-.020 on a track engine. This allowa plenty of oil flow through the bearing to cool it. But the added clearance makes the rings work harder, but the excess oil on the bottom of the pistons keeps them cool.

[Mark's 37]

Originally Posted by Ol' Ron

Ya gota work with the math, The diameter of the crank subtracted from the bore of the rod and tne thickness of the bearing times two, If the numbers add up and the clearance is right. THEN start fitting them. Also you must check for width , especially in the filit radius of the crank. You don;t want to hang up there. I like .015 on the width of the bearing, this lets the oil out of the bearing. Next the rod side clearance should be .008-.010" on a street engine and .015-.020 on a track engine. This allowa plenty of oil flow through the bearing to cool it. But the added clearance makes the rings work harder, but the excess oil on the bottom of the pistons keeps them cool.

Ron,

Edited and corrected the measurements:

My numbers are rod bore = 2.220" minus 2 x .125" bearing thickness(.250") = 1.970" minus crank journal 1.969" = .001" clearance.

Isn't this clearance too much?

[GOSFAST]

What "undersize" brgs are you working with, that shaft size is .030" under!

Thanks, Gary in N.Y.

P.S. I may be missing something with all your numbers but you cannot run .011" (rod brg) clearance??

[Mark's 37]

Found the error in the math I was doing. Clearance now is .001". The spec I found says .0005-.003". Fat fingers on keys.

The question remains that the bearings are egg shaped. When I sized the bearings to get clearance on the ends, the center part of the bearing is too wide and it won't move freely. I am checking this in a vice, not on the crank itself, the side clearance isn't a problem at this stage. I am wondering if sanding the butt ends of the bearing halves where they meet could remedy this.