Babbit bearings

[Hickory]

This winter i wanted to pull apart my 29 engine to clean out sludge, clean cooling jackets and so a valve grind and check rings. Its a poured babbit bearing engine. Is there a different approach i need to take or is it Cut and dry likè a replacable bearing engine. If the babbit is good i dont want to mess with them.

[Loren]

Poured babbit bearings are a real speciality almost an art.

Yes there are people who do the work but it is not for the average person.

You can have the crank polished ( any automotive machine shop which grinds cranks can do that for you ).

They can measure it and tell you how close or out of spec it is.

Then you can clean the bearing surfaces and get a kit of “plasti-gauge”.

Follow the instructions ( I am sure YouTube has a video ) and you will know what your clearance is.

You will find shims under each bearing cap ( don’t mix them up ).

By selecting the proper shims you can tighten up the clearance.

So if the babbit is good, a careful mechanic can bring the bearings back into spec.

 

In the case of babbit needing replacement, its a lot more complicated and best left to the experts.

I have watched a friend do Fords A & Ts. The process has its secrets to get the babbit to stick.

Then you have to linebore the bearings to size ( with shims in place ) aligned with the cam bearings.

If you don’t get the center to center distance right, the cam gears will not turn or the cam chain will be too sloopy.

I went to the Model T Ford Club of America website once to find the center distance between the cam and the crank.

They had the goofiest figure listed carried out 5 decimal places. The accompanying story told how someone took the time to measure 12 engine blocks, then averaged the results.

Of course this guy was measuring with modern tools in decimals.
When the Dodge Brothers built the first Fords ( up till 1914 ) machinists did not measure in decimals and engineers did not design in decimals.

The blue prints were in fractions.
I went to the chart and found the closest fraction to the goofy MTFCA decimal figure and found out that if you had used its mean you would been within tolerance but off from the fractional mean. So its part art and part science with a lot of history thrown in, and not everybody knows how to do it.

 

There is another option.

The Ford guys have scoured the bearing books to find insert bearings they could use.

They linebore the blocks to fit the bearings and stack them side by side ( insert bearings usually come from smaller engines and need more of them to fit the long Ford bearings ). Easy peasy….until those bearings go obsolete.

 

A postscript to this is that now insert bearings are made to fit specially modified Ford blocks, because poured babbit is such a lost art.

You pays your money and takes your choice.

[Los_Control]

I think what you say is very true. If the bearings are good, you do not want or need to replace them.

 

While I bet the majority of people would replace bearings just because they tore the engine apart ....Not because they were needed.

This would be real obvious on a modern day race car where the engine was torn down in the pits between races .... They may replace the piston, not going to replace the bearings if they are still good.

 

They will disassemble the engine searching for a issue & fix it. Then reassemble the engine & run it.

The average person does not disassemble a engine between races. ..... So it is just naturally assumed new rings & bearings are required to put the engine back together.

 

1 hour ago, Hickory said:

If the babbit is good i dont want to mess with them.

That is correct. They would be replaced as needed, not just because.

There are a few youtube channels .... where they work with old steam engines & pour new babbit bearings. .... They do it because is needed. 

[Hickory]

I have rebuilt a good 300 engine in my carreer so i am a highly achieved mechanic. I dont want to touch the babbit. From your deep Insight loren i now know there May be shims to deal with. This is the usefull info im looking for. Anything else i should be carefull about 

 

[Hickory]

Another thing i noticed when i had the pan off the counter weight appear to be bolted on to the crank. Anything special besides location i should check on these.

[westaus29]

I have had a 29 Plymouth with babbit bearings since 1998. I initially refreshed the engine with cleanout, hone and re-ring, valve grind. Checked the bearing clearances with plastigauge and re-installed them using shims where needed, max clearance was 2 thou which I figured was ok. Ran fine, good oil pressure and did about 10,000m ok until oil pump shaft broke in 2012 and send bits thru side of block, bent one rod. Found another block, re-used old crank and mains and three of rods. Picked another rod to  replace the bent one, matched weight as well as I could, new pistons and rings from Egge, checked and adjusted bearing clearances, that is back in and still running ok tho oil pressure is a bit low, probably due to camshaft bearings (does not have any).

 

So the advice is babbit bearings are very forgiving and are best left alone unless you have real issues in which case you have to find an expert rebuilder (I do have a mate, a retired plumber who re-babitted his own 1927 Chrysler 4 and hand scraped them to fit but not for the faint hearted).

 

But if you plan to push the Desoto hard and unleash that 6 cyl you may need to rethink. I recently sent a couple of axle shafts to a mate who managed to snap his Desoto axle, luckily the same part on Plymouth and I had 8 spares, not likely I will ever need them.