LA rod bore size...

[pishta]

Any engine rebuilder know the bore size of the big end of a LA rod without a bearing? ie. what is it bored out to when its on the bore hone? I got 1 real tight rod and weant to check it with a mic. can I just measure the bearing thickness and subtract bearing clearance? Its slightly oval when its torqued down in my rod vise.

 

[67Dart273]

I once as' this myself........

http://www.forabodiesonly.com/mopar/showthread.php?t=264700

A quote from "How to Hot Rod Smallblock Mopar Engines" by Larry Shepard.

"The big ends ID (inside diameter) should be between 2.2500 in. and 2.2505 in. For high RPM use, it's recommended that the big end be sized two-tenths undersize or 2.2498 in."

 

[pishta]

Ok, as my bearings are 0.060 wide so thats about right? 2.125 +.120 + a few thou for oil clearance.

 

[moper]

Oil clearance should be measured with the bearing in the bore. The bearing shells themselves are not exactly the same thickness along their entire length and that built in eccentricity is what gives you the clearance with the rod cap torqued.

 

[krazykuda]

Yes. to properly measure the clearance is to measure the crank diameter. Then torque the rod cap on the rod with the bearing shell in it, and then measure the diameter in a few different places. Then subtract the readings for the clearance.

 

[CPMotorworks]

Some guys try to use a ball mic and subtract the bearing shell thickness from bore diameter. Doesn't make sense to me but...
Check the bearing at 12 & 6, as they get wider at the parting line to account for stretch/rods pinching tighter at parting line.