Babbit question

C

chambies

Senior Member
Quick question about the Babbitt in my model a engine… I took the block apart and all the Babbitt surfaces look good except for the rear main cap. As you can see in the pics. Can the cap be done alone and repaired or do all need to be done and align bored? Does anyone in so cal still do this or have experience to look at it. It seems that inserts can be pricey.
Trying to get a good block together for a 4 banger belly tank build.
Thanks fordbarn!
 

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Look around for a used cap that is in good condition then fit using Timesaver.

Usually Belly Tank means racing. Do you plan for a run at a dry lake?
 
Thanks for the reply, I’m assuming that Timesaver is some sort of lapping compound?
Yes. Planning on running the dry lake and eventually Bonneville. Just trying to get built and starting out. Not going to be competitive for records… just the challenge of the build and the process. Thanks!
 
what is the size of the crankshaft, to get a cap that could fit you need to know if the crankshaft is standard size or undersize
The rear main babbitt in the block looks pockmarked in the picture.
There’s a different in what you need for a flat out maximum rpm engine and a putter around going for ice cream engine.
 
There are those who have "buttered" a cap and build up on the existing babbit to "mend" a broken out bearing. My thought is the chances of long term success are probably pretty small. As some have said "The Ice cream/parade car engine.

The best fix WOULD be to have the babbit removed, recast using the molds, peined and then bored out line bore style using the existing two mains as the guide.

Or at least part of the guide. In real life the benchmarks are relative to the camshaft and the parting flange of the block. Who knows where "wear" has brought the two better crank bearings.

Its almost like if you're at that point, just bore larger the other two bearings which then you consider installing a new crank. This might allow you to "save" some babbit pouring by re-use of the existing.

Ice cream looks better & better all the time...splurge and get a waffle cone.

Kidding. Anything Model A is worth doing "better." Ice cream sandwiches work.

Joe K
 
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Where do you live? I run V4/BFL at Bonneville, and can perhaps be of help. I live in Temecula, CA. I'll look to see if I have a main cap, what size is your crank?
 
I would not recommend doing a cap only because it's hard to find what the clearances are for the other bearings in the block. Did it have shims and if so how many? It would be very difficult to cut the new material down to fit the specs of the worn part. There's also the thrust bearing to be concerned about. Best rule of thumb is to check the crank out for cracks, runout, and wear. If it's still concentric and journals are all the same and good then that's where your going to save funds because there is no good substitute for nice new babbit in the block and caps. It starts over with new shims too so it can be made to last.
 
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Ok. Great info guys appreciate the help.
Looks like I need to take some measurements of the crank and real seal to see if it’s worth moving forward with existing Babbit. I do know that there was brass shims under main caps when I took it apart. I can get back with the measurements soon.
I guess finding someone in the so cal area that does Babbit and has the tooling would be a key component.

Jim Brierley:
Thanks for the offer of assistance. I am in Costa Mesa. My Dad has been out to your house a couple of years ago when we had a cam regrind done. This was in a different motor and we loved it.
 
There was a Beautiful polished belly tank at the GNRS in Pomona this weekend
Someone was commenting on taking it out to Bonneville or ElMo for a run
The problem is that the car is not constructed properly for running at a sanctioned event
If you do wish to run your build get the rule book and see if you can build to safety specs

Just a little tip before starting

J
 
I have myself a rulebook... first goal is to make a rolling chassis with engine and trans, then focus on the roll cage and pertinent scta rules.

I finally got around to measuring the crank journals on our model A engine. We know that this will not be race ready... but rather something to get running and started.
The crank measures as follows:
Mains
Front 1.597
Middle 1.585
Rear 1.593

rod journals
#1 - 1.47
#2 - 1.47
#3 - 1.471
#4 - 1.474
Any thoughts on these numbers. I am looking for a rear main cap with good babbit that I can install. I would love to learn how to babbit and machine it myself someday!
Thanks fordbarn.
 
The main journals were 1.625" when new and rods were 1.500". It's around. 030" under size now but that center main is way out there. The center main takes more abuse than the others so it's not all that unusual. The rods are consistent with .003" wear.
 
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Here is a pic of my tank with upper body removed
V4/GL class
 

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Rotorwrench, Isn't 1.500 minus 1.470 equal to 0.030 not 0.003?

This engine is tired. Good for fitting things out and trial running only.
 
Yes. Brain fart. I got the 3 in the decimal in the wrong place. It's basically a .030" undersized crankshaft so it's definitely had work done on it before. It looks like the tinning on the rear main cap wasn't ideal or it wouldn't have broken up that bad.

The inconsistencies are the larger than .030" undersize journals. Accounting for wear, the crankshaft may have been turned to .025" under and then had wear to get it to near .030". With poured babbitt bearings, a crank can be turned to whatever cleans it up since the bearings can be adjusted to fit with the align boring process.
 
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Hand fitting main caps and racing don’t mesh.the problem is racing in general, you turn around and the wife is gone and the kids are wearing other people’s clothes..take a real close look at John and Jim’s tanks and weigh your wallet to see how much weight you’ll lose racing
 
great information fordbarn. thanks! Looks like I will learn what I can from this engine and use it as a mock up block for the build.
 
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