Bearing Clearances, Shims

[MikeC5]

Since I dropped the oil pan I figured I might as well check bearing clearances. My question is about the concept of adjusting the shims to tighten up clearances. I normally plastigage at the center of the bearing cap. The number 4 conrod checks out large (3.5 to 4 thou). If I remove a mil or two from the shim thickness, don't you end up with less than round bearings? I was also surprised how thick the shims are; 0.120. Although they appear to double as spun bearing preventers. I know the Joad family did it on their Hudson but is it a good idea?

[MCHinson]

A number of argumentative posts have been deleted from this discussion. If anyone is able to help MikeC5, please respond. Additional argumentative posts will result in further deletions and additional measures by the Moderators.

[1936 D2]

Thanks for watching Matthew.

[TonyAus]

Mike

Yes, removal of shims will result in an out of round bearing. At this point you pull out your half round scraper and bearing blue. Apply a thin coat of blue to the journal and refit the rod, giving it a half turn. The blue will show up the high spots which can then be gradually scraped down. About an hour of hard work should get you there.

[R.White]

No arguement; Tony you are dead right. The only arguement I ever had was with my old Dad who would have nothing to do with the practice. He is a retired engineer; used to more precise ways of doing things. I, on the other hand, am a humble mechanic who is used to' fitting' white metal bearings - just like the guys did it in days gone by.

Just don't try it on shell bearings!!! LOL

Now, let's be having no more arguements.... each to their own, I say.

[MikeC5]

What is the blue stuff called? I have a tube of Prussian blue which has the consistency of oil paint (and is non-drying). I've the blue stuff used for laying out lines on sheet metal called Dykem Blue, which does dry. For con-rods, the MIM (mech instruction manual) says to file down the shims and after tightening rod nuts rod should still be able to move fore/aft on crank journal with strength of hands or light tap with hammer. It sounds like I could set clearance via shims/plastigage and as long as rod can still more axially on journal (at several crank positions) then it isn't too tight (or out of round). I did mike one journal and numbers agree to within less than 0.001"; not too shabby.

[R.White]

I use 'Stuarts' micrometer engineers marking. It may not be convenient for you but for the record, the manufactuers are I.C.S. (industrial and consumer supplies), Teignmouth, Devon. England.

Only my opinion, but not being a pressure fed engine, the tollerances need not be too close, but I expect you will do just fine.

Ray.

[MikeC5]

Thanks Ray. I just want to make sure nothing is too tight.

[R.White]

Mike, I'm sure your Dykem 'high spot' blue will do the trick, no problem.

Sounds like you have a good crankshaft, there. I find that it is usually the number 4 (nearest the flywheel) that gets most wear; especially the main bearing. I would test for cracks if there is any doubt - better safe than sorry, I suppose. Still, it's your call; I'm sure you are having fun with the oily bits!

Ray

[MikeC5]

Yes indeed. I had a hard time getting my hands clean last night. I will measure all the con rod journals and see. I'm not sure how well the dye penetrant will work with an oily surface (this is being done with engine in situ). Worth a try though.

[R.White]

Sorry, I did'nt realise the engine was still in the car!

Please ignore what I said about the main bearings; if you attempt to dislodge the crankshaft to measure them (and I don't expect that was ever intended) you will regret it!

As I am sure you know, these old engines seem to be capable of an almost infinite amount of punishment, so unless your main caps are breaking up, just carry on with the big ends.

Have fun!

Ray.

[Guest 1930]

I use 'Stuarts' micrometer engineers marking. It may not be convenient for you but for the record, the manufactuers are I.C.S. (industrial and consumer supplies), Teignmouth, Devon. England.

Only my opinion, but not being a pressure fed engine, the tollerances need not be too close, but I expect you will do just fine.

Ray.

I though these were pressure and splash fed combination, I guess I will have to look into this as well so I am clear,

Ray you seem to know alot about some rebuild procedures, all great info. Too bad we cant figure out a way to put all of this together. I know very little concerning babbit engines when it comes down to nitty gritty stuff but as my initial post said in this topic which got deleted ( BTW I was told by the moderator that it was deleted because it was easier to delete everyting and not because of anything wrong with my post ) I have tons of literature that are filled with information concerning this and could be found if a person were to spend a bit of time thumbing thru them.

I had offered to send Mike some of it and I suggested that he take his time and then really take his time and figure out what he doing by reading up on it before he attempted anything daring but it looks like its too late for that now so I wish him luck.

Edited April 15, 2012 by 1930 (see edit history)

[R.White]

Yes, Jason, the pressure feed from the pump to jets in the crankcase squirt oil into chanels in the crankshaft, if my memory serves me, so the bearings are not exactly pressure fed as I see it. But better than the older kind of engines (not ours) which simply scoop up oil from the pan and hope for the best!

Ray.

[MikeC5]

That's right Ray. There is a tube that runs down the right side of the crankcase with small holes drilled in, pointing down, over strategic locations. The rods do still have oil scoops (holes really) on the caps. I would expect it does a better job than random splash oiling. My plan for the engine is to do a thorough going through in another year or two. This was just to make sure there were no glaring problems inside the crankcase. The mains all checked good at ~0.002" clearance and I did make some small adjustments to two of the big ends. Since such a small amount was removed from the shim, I used a 1/2" thick glass plate (for a flat surface) and 320 grit emery to carefully remove material. Just from looking at the sanding patterns on the shims it was clear these were not especially flat as installed. I also found two of the con-rod bolts a bit loose (although the cotter pins were still in place) and the bolts had an extra ridge on the shank as a result. Luckily, I did have extra bolts in the small cache that came with the car. These could have resulted in an unpleasant surprise!

[R.White]

That sounds pretty much text book stuff to me, mate. Ed China would be proud of you.(wheeler Dealers)

By the way, are your con rod bolts, or big end bolts, I call them, fitted with castellated nuts and split pins - what I think you called cotter pins?

I can't tell you how lucky I was to find that my 5 bearing 'c' engine was in good shape. I don't know much about it's history, but someone must have done it up in the past. She fires up easily and runs well without any knocks or rattles. There is a little smoke at first but that soon clears (although I think she may be running a tad rich) and the feeling I get is that she just wants to get on and GO!

The next time I get a chance, I will check the valve clearances just in case the exhaust valves are a bit too close. As you probably know, a quiet engine could be hiding tight exhaust valves and the last thing I want is to burn one out just as I have got her going!

Best,

Ray.

Edited April 15, 2012 by R.White (see edit history)

[MikeC5]

Yes, castellated nuts & cotter pins. It's definitely better to set the valve clearances a little toward the loose side.