Can anyone tell me the thickness of the block half Babbitt in a T's main bearing? My crankshaft is still stock and within limits according to the book. The Babbitt in the block still looks useable and there were still a couple of shims under the caps, although I intend to replace them. If I can get away with just replacing the caps with re-Babbitted ones I may save myself the cost of a repour and align boring.
On a different note, I miked the cylinders yesterday and they're all .050 o.s.! To the best of my knowledge no one offers such a piston size, so I'll probably have to go to .060.
Half of the c.s. dia is about .625", so the bottom of the original stock babbitt should be roughly close to .625" from the flat area on the block that the cap bolts to... Measure with a depth micrometer or a digital caliper and strait-edge.
Perfect! Thank you Adam.
If your bores are now at .050, and they're not in good enough condition to use, then they're also probably too bad to clean up at .060. Ask yourself if just a light honing will do, versus going up to .080.
If your block babbitt looks good I would use it as-is, as you suggest. But, take very careful measurements and be certain that the center main is not more worn than the ends. It usually is. Lay your crankshaft in the block. Put a dial indicator over the center main journal of the crank and push down hard on the crank. See if you can deflect the crankshaft into a void, indicating the amount of center main wear. You could also blue the 3 mains, roll the crank around in the block with no bearing caps, and see if all 3 mains show contact with the crank. If it's not too bad, you may be able to scrape the end mains enough to get them in line with the center.
The first and the third main wears in the caps, while the second main tends to wear in the block, so it's best to carefully check for wear in the second main with a steel ruler long enough to go from first to third.
Moderate wear in the second main can be fixed with lots of work by scraping the first and the third main until they're level.
Timesaver lapping compounds helps when lapping in babbitt and bronze bearings: https://www.modeltford.com/item/TIMESAV-Y.aspx
With all three mains in line in the block, then it's no problem to reuse the caps you have by removing shims or sanding the caps some - the babbitt is thick enough for some adjustments.
But you may first want to have the crank shaft checked for cracks by magnafluxing while you have it apart..
The problem is often the axial play, controlled by the third main cap. The clutch spring pulls the crank shaft to the rear when the clutch is disengaged, thus there's often wear on the thrust surface, allowing too much distance between the flywheel magnets and the coils. Thus not enough magneto output.
It's possible to repair the thrust on the rear main cap by soldering on some more babbitt and carefully file it to fit - or if you have a lathe, it'll be even better (see article)
Not knowing all this stuff, I fitted new caps to my block and have been running that way for many miles. I reasoned that the thrust was to the caps and if Ford didn't babbett the block in the early T's I would be fine. Not suggesting anything, just telling my experience.
Well, I may have blown it. Mac's was having a 20% off sale this morning and I ordered a set of .060 pistons and rings. I can only hope they have a good return policy if the bores have to go to .080!
As for the mains......this was shattering. First of all, they all measure the same depth end to end but there's no sign of oiling grooves. What did they measure? Well, about .100" oversize! Looks like a repour and align bore is in my future. Ouch.
Update: I managed to change my order at Mac's (no small feat with their call volume today) and ordered standard size pistons and rings. I'll bite the bullet and have the block sleeved since I know I'll be happier with that anyway.
Also, my first measurement of the main bearings didn't make any sense so I remeasured them and they came out as VERY close to standard after all. Makes sense since the crankshaft miked the same way.
Note to self: brush up on reading a depth mike correctly!
I have a different tho related question. I have a block I'd consider putting a 1.50 inch Scat crank into. Do the mains need to be bored oversize and repoured or is there enough babbitt to bore to the larger size?
Noel, you'll need to bore the mains oversize and repour. Not only that, you'll need special main bearing caps too - and some other modifications to the pan since the larger mains only comes with a longer stroke version, I think? But your T engine will be bullet proof
There is no reason to sleeve a block that is .050 over- either hone it to .060 or bore it to .080 and run it. The rough main saddles in a block are pretty close to 1 3/8" dia. The large Scatt mains are 1.600 as far as I'm aware.
Dan McEachern makes and sells the big main caps.
Nice looking pieces at a good price.
(I just bought some)
Did you Mic the bores? I once did a block that the pistons were marked .050, and I had some .060 pistons on hand, so I sent it out to be bored to my pistons, which they did, and then informed me the block WAS standard before they bored it!! If it had been my shop I would have called me and asked first, I would have been happy to have ordered .010 or .020 pistons and saved the block metal! I'm guessing that 'back when' the rebuilder resized some pistons they had on hand and left the old size markings on them.
I have seen .003, and .005 thousandths over size Ford pistons.
Yes, I miked the bores and they're all .051 o.s. (or very close). Unfortunately, two of the cylinders have deep rust pits and I don't think they would clean up at .060. Maybe at .080, but that's getting kinda thin, so I decided to sleeve instead just to get some strength back into the block.
Must have been some oddball pistons.....and iron ones to boot! Too bad they weren't salvageable.
I just sent an email to L.A. Sleeve with my requirements.....hopefully they have a stock size that won't cost half the national debt.
With out looking it up, read in one of my parts books once, pistons came in .005" steps all the way up to .120" in cast iron, even in semi finish as well to machine to fit the bore size, sold per one, not in sets as it was common practice to only repair or over size one or more bores as needed.
Thank you Frank.......that makes sense. I'm only familiar with the current practice of .020" steps and being sold in set.
And I wouldn't worry about a few pits in the cylinder walls, probably won't effect oil consumption at all. We're not building high speed racing engines here!