Engine: Rod bearing clearance

[studevic]

Hello all , i am trying to rebuild a 289 , it has standard crank and bearings , shows 65 thousand miles on speedo. So i plastigauge the all the rod bearings and get around 0.002 to 0.003 , the shop book says clearance 0.002 to 0.005 i think, my old brain is not as good as it was , so do i understand correctly that i can use a new set of standard bearings or do i go slighty oversize , the crankshaft looks good. cheers

[StudeRich]

Your Rod bearings must be in pretty good shape if that is all the clearance you have.
Studebaker and some aftermarket Brg. Mfg's. did sell .002 undersize bearings, but very few NOS examples can be found today.

However in your case, that would be Too tight, so with virtually NO wear Standard Bearings are what you need if you choose to replace them.
Just make SURE none of the Crank throws exceed the limits, by double checking them by using a Mic.

[Bud]

According to my shop manual, the rod bearing clearance in a 289 should be between .0005" and .002 thousandths. If you are seeing .002 to .003 thousandths you have too much clearance and the crankshaft should be measured for dimension, taper and out of round. If you have .003" clearance, you will have low oil pressure and possibly excessive oil consumption due too much oil being thrown off of the rods and on to the pistons. I aim for .001 to about .0015 thousandths clearance on the rods for a stock engine when I do a rebuild as that gives higher oil pressure and lower oil consumption. Bud

[Jeffry Cassel]

Ditto Bud. I like .0005 and .0015. Don't like > 15 10,000ths. Guess the ? is what did you Plastigage?? If the old bearings you need to replace. If new, you might still be able to find .001 os bearings. At any rate, clearances are twice what they oughta be.

[64studeavanti]

To be sure, mic the crank as others have suggested. Yhe bearings will wear before the crank. You may only need to have the crank polished.

[studevic]

Hello all , thank you for your advice, however i have found i made a major mistake when checking the rod clearance , i used the wrong plastigauge , i used the red type when i should have used the green , so i did all the rod bearings again with the green Plastigauge and got readings from .001 to .0015 , this was with the old bearings on the rods , thank you again .

[JoeHall]

With that good clearance, if the crank journals and rod & main bearing surfaces also appear OK, I'd reuse them. During disassembly, I'd label each one so as to put it back in exact same location in reassembly. I would NOT reuse them if I messed the labeling up, due to possible rotational changes.

I say this not because I am cheap, but because most repro bearings ain't same quality as OEM, and since most come in plain white boxes, country of origin is difficult to discern. The best repros I've seen were made by King Bearing Co. in Israel, but they've gotten scarce. Sometimes you can find name brand bearings, i.e. Sealed Power, but they're getting scarcer.

[yeroldad]

I am very leery about reusing bearings that have been 'sitting around', soaking in detergent oil. I have seen motors that had good looking surfaces, and good clearances flake, and that results in chewing up surfaces.

[irish]

With that good clearance, if the crank journals and rod & main bearing surfaces also appear OK, I'd reuse them. During disassembly, I'd label each one so as to put it back in exact same location in reassembly. I would NOT reuse them if I messed the labeling up, due to possible rotational changes.

I say this not because I am cheap, but because most repro bearings ain't same quality as OEM, and since most come in plain white boxes, country of origin is difficult to discern. The best repros I've seen were made by King Bearing Co. in Israel, but they've gotten scarce. Sometimes you can find name brand bearings, i.e. Sealed Power, but they're getting scarcer.

I second this statement! A few decades ago I would have said "buy new bearings" but not today! I would use the bearings you have. At my shop we have seen alot of problems with these recent asian made rod and main bearings.

Joe

[swvalcon]

Joe Look on rock auto and see if you can find what ever bearings you are looking for listed by Engine Tec. They are king bearings in a plain white box. The bearings in the box have all the king bearings marking and you are going to throw the box away so who cares what color it is. I used King bearing over 30 years ago even in our race motors and never had any issues with them

[tcabman]

Hello all , i am trying to rebuild a 289 , it has standard crank and bearings , shows 65 thousand miles on speedo. So i plastigauge the all the rod bearings and get around 0.002 to 0.003 , the shop book says clearance 0.002 to 0.005 i think, my old brain is not as good as it was , so do i understand correctly that i can use a new set of standard bearings or do i go slighty oversize , the crankshaft looks good. cheers

R.A. , I sent You a PM.

[swvalcon]

Plastigauge is just a ball park and will tell you if you have a major issue. If you want to know just what you have you have to mic your crank and torque your rods and main caps with the bearings in place and inside mic those to know for sure. .002 is not a problem .005 is getting a little to loose but don't jump the gun until you know for sure that .005 is real.

[studevic]

thank you Joe, i will get back to you in the near future , cheers from roger