Shimming rod bearings

The shim packs are .010. You can set the bearing cap on and check with a feeler gage to see close to where your at before shimming. the best way is using a mic to check the diameter of the journal and also the ID diameter of the bearings.
You can also just use plastigage and check several times as you shim.

Do you have a fresh reground crankshaft?

They'll probably get the rope out when they read my formulation… I was told by an old-school mechanic (before plastigauge was invented) They would start with some shims installed, then pull shims out until they could no longer slap the rod forward and back with a mallet. Then they would gradually pull shims until it could be knocked back and forth with the mallet, then pull 1 more and leave it at that. Should have a little bit of wiggle room on the rod then. They said this applied to all engines, full pressure or dippers.
Maybe not very professional, but supposedly it gives you your ~.001 clearance.
When I did a re-ring on my B, I didn't grind the crank, I just made sure the rod being shimmed was at the bottom of its stroke. I was told when the rod is at the bottom of the stroke is where the most wear occurs, so if you get your plastigauge reading there, and the clearance is good, the rest of the circumference of the journal should be good as well.
Again, I don't think it's very professional, but it worked for me.

What do you think guys? Is my commentary alright, or should I just stick to combines and leave the engines to somebody smarter? Lol

Edited by CrestonM - 18 Oct 2017 at 12:10pm

Yes Doctor, I know that, and I do think,  but the 50 year old shims didn't fare so well during disassembly. I was as careful as I could be taking it apart, but some pretty much ripped and disintegrated. So I was going to start from scratch and was looking for a starting point without having old ones to measure.

Edited by littlemarv - 18 Oct 2017 at 3:43pm

I've been inside old farmalls that had newspaper as the shim material...  Plastigauge is the easiest way, IMHO...

If you are "close" and you take out what you think is right,  ALWAYS try to rotate by hand to double check.. If it has some resistance, then add back .001 shim .......... always check rotation by hand between different bearings shimming... not much on rods, but if the crank is .001 - .002 out of LINE BORED, then you might have to add an extra shim on one bearing and be toward to TOP OF THE CLEARANCE LIMIT to get the crank to turn smooth... no matter what your plasti-gauge says.

DougS wrote: Creston: Wouldn't shimming where the wear is the greatest result in too little clearance where the wear is the least?

That sounds plausible, but I'm not sure. Just what I was told.
Or maybe I had it wrong in my memory… Maybe that's where the least where occurs?
Don't take that to the bank… I'm no expert.

Edited by CrestonM - 18 Oct 2017 at 8:06pm

The greatest wear is something like 30 to 45 degrees after top dead center where the force from the combustion is greatest. Wear in the insert and on the crank journal. I have seen that wear go all the way through an insert in wear into the rod in an air cooled VW.

As I remember from the VW shop manual, one check for adequate clearance is that the rod will fall just from the weight of the rod without a piston or piston rod. Less force than turning by hand.

Gerald J.

I must be an Old Timer cause I know they will run a little loose, longer than a little tight, But I've used mics to check sizes of things I worked on for 40 years.