m37 rod bearings ?

[Travis69]

Hi there fellow M37 enthusiasts,
I am trying to figure out what size rod bearings I have in my rig. They say 3755 on the backs. The crank measures about 2.064 and the rod bearings around 2.069
is this about the right clearance ? I would like to refresh it with new bearings. Any help getting this old girl back on the road here in Colorado would be most appreciated !
thank,
Travis

 

[OutpostM37]

Welcome aboard Travis.
I have an M37 230 crankshaft that is cut .010" / .010" I measured one of the rod journals which gave the following reading. 2.052" This is a crankshaft that has some mileage on it. I want to say that your crank is at standard. The factory had tighter bearing clearances from what I have read, usually around .0015". My current rebuild (different crankshaft) had all the rod/main clearances at .002" Here is a pic of a bearing back for the old crank that was .010"/.010" Best of luck on your new project.

 

[Travis69]

Hi there and thanks so much for the reply. So do you think I should run standard bearings again ? So far all I have found are .012 over. Any idea where I could find std. ?
thanks,
Travis

 

[Roller]

Midwest Military or Vintage Power Wagons should have them.

Frank

 

[OutpostM37]

Travis,
Have you performed a compression test or a leak back test on the engine? You may need to do more than just bearings. Most say that a flatty 230 that has compression 90psi or below will need new rings/cylinder bore & hone also.
The Carter Ball & Ball ETW1 carburetor needs good vacuum to properly operate the accelerator pump in the carburetor. Low pressure in the intake manifold/caburetor passages overpowers the spring on the backside of the accelerator pump piston. This vacuum will pull the piston up. When the gas pedal is depressed, vacuum decreases and the spring will push the accelerator pump piston down forcing fuel to the engine. The accelerator pump does NOT operate when the engine is not running, opposite to newer carburetors which have the accelerator pump function mechanically and feed fuel as long as there is gas in the float bowl.

 

[GUNNY 155]

Usually the bearing shell will have its size stamped into the back. IE std for a standard size, 010 for 10 under 020 for 20 under.