Several years ago I acquired an overhaul kit for my 1943 military GMC 270 from EGGE Machine. Now that I'm finally doing the engine work I opened the packages or rod & main bearings to find a light layer of corrosion on some of the bearing surfaces. I wasn't concerned about them since they were sealed in plastic but didn't realize they were just shrink wrapped to a piece of cardboard. The cardboard backing must have allowed some moisture to enter and cause the corrosion. If the factory had put any oil on them they'd probably be ok, but they were completely dry.
The rods aren't as bad as the mains but some still have a dull and slightly rough finish. Are the salvageable? I used some oil and wiped a couple of them but it doesn't seem to help.
I was able to locate a set of .030 under Clevite rod bearing off e-bay....we'll see if they're ok.
The only place I see 0.030 under main bearings available is from Jeepest in France. They're NOS so who knows what condition they'd be in. Anyone know of other sources?
I see some are listed as 1955 and later. Is there a difference in the main/rod bearings for later years? I know early on there were two types, one with thrust bearing integral to the main bearing and one with thrust bearings that were separate pieces pinned to the block but either could be used.
There were 2 different "widths" of rod bearings. You should take a look at THIS post.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Those bearings are probably OK. Rod and main bearings are made with a very thin top layer of pure tin (less than .0005") to assist in quick "wear-in" to microscopic irregularities in a crankshaft surface. I'd suggest soaking a piece of 4-0 steel wool in clean oil, and give the pitted area a gentle rubdown, followed by a thorough cleaning with solvent. That's how us gunsmiths deal with flash rust on blued firearms, without doing any further damage to the bluing. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I'm with Jerry that they're likely fine. Even with deep pits, and most of the bearing surface intact, they should last a long time. A bearings job is to hold a film of oil which actually supports the shaft, and as long as the clearance isn't excessive, the only time the shaft actually contacts the bearing itself is on a dry startup.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
Pits just trap extra oil- - - - -high spots or imbedded hard particles are what damages crankshaft surfaces. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I'll try cleaning them with steel wool & oil as suggested. Right now the surface feels like it has an oxide layer that might be raised on the surface but hard to tell. I wouldn't be concerned if it was slightly pitted. Hard oxide particles on the surface doesn't sound like it would be good.
There were 2 different "widths" of rod bearings. You should take a look at THIS post.
I looked over that old post and I'm not sure if I'm clear about changes.
I'm working on a 270 out of a WWII 2 1/2 ton CCKW. It has the #2135419 rods with .990" pins, a 2.456" big end bore and 1.2" wide bearings (which appear to be the "wide" bearings)
What I haven't been able to find are the dimensions of the rod big end bore and crank diameters on the 1956 and later engines to see if those bearings are compatible with my engine.
Attached from '57 GMC Maintenance Manual. Covers both 270 and 302. No differences between 270 and 302 in "Connecting Rod" portion of the specs.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
From the Federal-Mogul shop specifications manual #115 1982 edition:
1940-51 270 F/M connecting rod bearing number 9845CP STD diameter 2.3110"-2.3120". Width 1.212"
1945-52 270 F/M connecting rod bearing number 1905CP STD diameter 2.3110-2.3120" Width 1.107"
It looks like there was some overlap in certain years, so it might be a good idea to measure the big end width of the connecting rods or your original bearing shells.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
