Checking bottom end bearing clearances

[40 Deluxe]

Yep, it is a job. How about using a dial indicator and move the crank up and down to measure the clearance? The bad thing is you won't get to see the condition of the babbitt.

Interesting! A few years ago GM came up with a special tool for checking rod bearing clearances that clamped on the crank and had a dial indicator that read off the bottom of the rod. I never saw one; just pictures in the factory shop manual. I imagine that it cost dealers a pretty penny!
I would think oil viscosity would be a factor. Dial indicating an A main with 30W or 40 oil in it may not give an accurate reading. Modern engines with 0W or 5W something oil may "squish" the oil out to get a true reading.

 

[Jim Brierley]

When you removed the 4 shims from the rear bearing, you removed only .002" of clearance, (.002" straight down)

 

[Licensed to kill]

When you removed the 4 shims from the rear bearing, you removed only .002" of clearance, (.002" straight down)

The shims are .002 each (I mic'ed them).

 

[Licensed to kill]

Mr. LTK,

This art of adjusting Babbitt bearings is not any different from trying to find a single craftsmen in 2017 who can successfully build a boat by cutting wood planks with a hand saw & shaping rough wood planks with a carpenter's hand plane; yet, why was it successfully done so often in Model T days?

I believe that most (if not all) of the old time craftsmanship methods have not been handed down because, other than for hobbies, they are too labour intensive to be of much use these days. back in the day, a mans labour was cheap, today labour is the most expense part of building something.

If after adjusting the shims, if the crankshaft cannot move easily sideways, Babbitt adjustment is too tight.

Not sure what you mean by "sideways"???

All vintage mechanics I knew in our area could feel individual, adjustable up & down journal movement and rotational tightness after wiping off and removing the film of oil on the journals and Babbitt.

If an individual could not successfully perform this task after hands on training years ago, (and there were some), they were never trusted to try to allow them to continue try to do this type of work.

After 20 years of reading Model A Forum restoration messages about all of the Model A engine knocking & Babbitt failures right after engine rebuild, there is a definite learning gap where this art of Babbitt adjustment and craftsmanship was never handed down through generations.

The advent of plastigauge has made these skills pretty much obsolete for all but the die hard traditionalist I would think. However, checking clearances while the engine is IN the car adds a challenge to plastigauge as the crank is no longer resting in the block but, rather, is "hanging" from the remaining mains which, like others have mentioned requires the crank to be pushed up tight in the block to get a proper reading. I appreciate your input as I'm still trying to learn to get the proper clearances. I'm too old and will not need to do this enough to invest the time required to learn "the old way" as much as it fascinates me and I question if one can learn it just by explanation but rather would require hands on learning from someone with experience. No idea where I would find that. I love reading about it though to understand the concept.

 

[Kohnke Rebabbitting]

So while I have the pan off I wanted to check my bearing clearances. Did alot of searching and due to necessity (can't find any plastigauge locally) decided to do the go-nogo method. Kind of a hokey way to do things but most things about these cars is kinda hokey and they are not exactly precision pieces of equipment. Started with the rear main since i already had that one off to fix the missing oil tube issue. With 4 shims removed, the crank turns freely and drags with a piece of .002 tin foil in but does not lock up. remove one more .002 shim and the crank drags with no tin foil. Seems too snug to me and to my way of thinking if it drags with .002 foil in there, then the actual clearance would be something like .0015 would it not??. Drag suggest to me that there is virtually no clearance. I'm thinking go with the 4 shims removed rather than the 5. Am somewhat surprised that I had at least .004 too much clearance (2-.002 shims from each side.

Make a .001 shim for one side, or you can use a hand made .001 on each side, what ever get the job done.

Herm.

 

[Kohnke Rebabbitting]

Someone compared Plasti-Gage to SOFT CHICKEN POOP, you know what that WHITE stuff in Chicken Poop is????---It's Chicken Poop, TOO!!!
Bill Inquisitive

Bill, is there any taste difference in the white, then the rest of it?


Herm.