39 Dodge flat head 6 rebuild questions .

[Airborne Ed]

Back here again , While waiting for the valve spring compressor to arrive  ,I was looking at the rod and main bearings today . I pulled all the bearings out of the rods and I see no 3 piston had a .002 brass shim behind the bearing and all the mains except the rear main also had brass shims behind the bearings .This is the first time I came across a engine having this . It's my first flathead that I am working on. Over the years I have torn down a few ohv's ,however never came across shims behind any bearings  .

I'm pretty sure the lower end has never been rebuilt . My question is would this be fairly common back in the day ? I don't know if someone screwed up machining the journals when the engine was built . I know the history of the engine repairs was a head gasket and milling of the warped head . It looks to me that 2 valves might have been replaced at some time . The reasoning I have is all the other valves have a straight screw driver slot across the top of the valve and 2 don't have any slot . I haven't Miked the crank journals yet 

 

Any feed back would be welcomed ,guys

As always thank you for any knowledge you can share on this engine.. 

[Don Coatney]

Shimming of bearing inserts is not a recommend practice but I have talked to at least one person who has done so and he is also from Pennsylvania.

[Airborne Ed]

I don't know who did it ,I thought it might have been the factory like I said ,Don

 

[Plymouthy Adams]

factory has special bearings to address the undersize attributes...

[sser2]

Shimming was a factory-recommended procedure when original main bearing caps were to be replaced for some reason. But those were shims at cap mating surface, not under bearing shell. A shim under shell is a no-no, definitely not something that was factory-installed. You will need to assemble caps without shells, applying specified torque, and then check for out-of-roundness before installing new shells.

[Sharps40]

Shimming rod and main bearings was common with babbit bearings.  However, Chrysler was one of the first makers on the market with insert bearings and prohibited shimming insert bearings.  However, at the time, and even into the late 50s/early 60s on the GM 6s, shimming continued on both babbit and insert bearings because it was how most mechanics were raised up....shim babbit bearings and the insert bearings were not common.

Your proper fix is as mentioned.  Condition, size and true of all the main and rod journals, caps, etc, machine as needed and fit new proper sized insert bearings with out shims. 

Edited November 2, 2016 by Sharps40

[Airborne Ed]

Thanks for the info ,guys. I intended to have the crank machined because of that and a few small scores (scratches ) on a few of the journals. I guess I can assume that the lower end was touched sometime in the past ..

Ed

[Plymouthy Adams]

usually a crank is stamped with undersize if done at machine shop or by the factory at install, yes even the factory cleaned damaged cranks with resize ....look for this info on a counterweight...BUT if only one journal was affected and not across the crank, each rod journal/main....you looking at a repair from beneath the shade tree

[dpollo]

putting shims behind the shells is not good practice. It is done to avoid replacing of shells and to compensate for a crank journal which is out of spec.  Shells were available in Std.  001, 002 and 003   as well as 010, 011 and 012   and 020  and 030.    This part of an overhaul is too critical to mess around with.  It sounds like your engine was given a patch-up at some time when the car was not really worth spending a lot of money on.   That it survived this long is testimony to the toughness of these engines and the inventiveness of people with more time than money.

[Dartgame]

I'd be certain to have the rods reconditioned and the block checked and align bored if needed.

[Dave72dt]

I don't think it was a common practice for brg liners to be installed from the factory.  I do believe it was more common out in the everyday world where money was tight and replacement parts cost more than some pockets could cover.  I've seen liners used a few times, usually on an engine that had spun the main brg/s.  You have to remember that align bore equipment was not available  at every machine shop and that the factory did overbore some blocks so rather than scrap and recast a block, the liners would be installed.  Even today you can find new engines with oversize brgs to fit the block bore and undersize cranks.  JMO

[Airborne Ed]

Thanks guys ,for the great info. after all the replies I have come to the conclusion that those inserts were done sometime ago by other than the factory. It truly is amazing that the engine ran ,the way the engine was filled with sludge and the cooling system as well.. I guess if I was 77 years old I may be that way too..