Inliners International Forums General Discussion Engines Need help with chevy 230 rod bearings

Hi all, new member here, first post.. pls don't shoot

I am freshening up a 230 (1970), and the rod bearings seem weird to me. I mean, something doesn't add up. The engine had low oil pressure at hot idle, but I have put thousands of (easy) miles on it since I bought it in 2007. No modifications. Everything bone stock. I used good oil at every oil change.


Ok, here's what I found:

Rod bearings are worn to "copper" in the mid section of the top bearing half. They are marked STD.
Rod journal measures 1.995"
Bearing shell measures 0.0610 at the tip.
Have not plastigaged the rod bearings yet.

Chilton book says rod journal diameter spec is 1.999 - 2.000"
Oil clearance spec is 0.0007 - 0.0027"

I'm already 0.004 below spec on journal diameter, so with std bearings, my oil clearance could never be less than 0.0003 + 0.005 = 0.0053.... way out of spec, right?

I'll plastigage as soon as I get a chance. But what do you think, do I have wrong size bearings on there? What size should I try first?


The undersize bearings jump from 0.001 to 0.010
0.001 would only get me to 0.0043 oil clearance, still way too much... 0.010 would get me... in a bind

What is going on? Am I looking at things wrong?

I don't want to have the crank machined. Can't afford it right now, too much work too. Doing this in less than ideal conditions outside.

Thanks for any insight or ideas, comments.

Jan

meant to plastigage mains and rod journals tonight, but it got dark and something big was stomping through the woods behind my shed so I thought it best not to let it catch me while I'm under the car... we have black bears here

Sounds like whoever rebuilt it should have reground the crank, but only polished it instead of spending the money to do it correctly. It will need to be reground, as you see, it will still have bearing clearance that is way too much and again provide low oil pressure if you leave it like it is.

Thanks, that's what I think it needs too. And grind all of the journals. Hate it when I find an engine with mixed size bearings... lol. Seen that too.

I just want it back on the road as my weekend toy, no funds for a real rebuild right now. I did not expect to find this inside, it ran so well for so long. Had no problema other than low oil pressure at hot idle. As soon as I touched the pedal the pressure would go up.
I may do it right within a year or two, dunno. That would include some power add ons then. Now I just want to putt around town on sunny days. The car is retired from active duty. Got another inline 6 for daily driver (Jeep).

I am pretty sure I will get the 0.001 bearings and slap it back together with those for now. Plus plastigauge to know for sure what I have there. There's always a chance for error in measuring stuff upside down under the car in the dark

I think you are right on with your analysis. If you really want to put it back together without grinding the crank I would do as you suggest and use .001 bearings and run it. Maybe use 20w50 oil.

In your situation I would be more concerned about the OEM 11/32 rod bolts with unknown history than a couple extra thousanths oil clearance. When you do fix it right I strongly recommend quality aftermarket rod bolts.

I see ARP bolts in my future... not my first engine project

I just plastigaged my rod bearings, on one rod. Got .004"

I think I need to do them all. But it looks like .001 bearings it is.

Thank you all for your replies. I had been measuring and looking at them for too long, starting to doubt myself and getting cross-eyed.

I'm done for tonight, need to study for an ASE L1 certification... exam tomorrow

Your main bearing clearances are probably going to be in the same condition as the rods, so you might not benefit much from just replacing the rod brgs. You can't plastigage the mains without the engine being inverted, have you even pulled a main cap out of curiousity to inspect them.

I'm doing the mains too. They are much better but since I'm there... I'll do those too. And a new oil pump.

How are you checking the main bearing clearances?