Splasher 6 Center Main Bearing Exchange

Unknown

Are the Center Main bearings on Splasher 6 Engines interchangeable? I have heard people mention that they obtained NOS bearings (the lower cap) and installed them on used engines. If so, do they have to be line-bored, or were there "standard" sizes? Thanks for any info.

Park_W

In '46 and '47 at least, factory replacement main bearings were available in standard and .010 undersize, in addition to the "unfinished" ones which were used when line boring. Though ideally one should have them all lined bored, if you could find one the right size, you can probably get away without line boring on the six cylinder engine. The eights, with their more closely spaced mains, are a little more touchy in this regard. We need for someone to come up with a jig to hold a pair of unfinished main shells precisely positioned while they're reamed to the right size. The rebabbitter I've used says he doesn't know of a way to do that. Even then, there's nothing like boring them while installed in the block of the engine they're going to be running in!

Uncle Josh

Junkie, the short answer is sometimes.



Park's babbitter needs a machinist. You can make the jig by bolting two bearing caps together. Probably hasn't got a reamer that big, but ya can bore it on a vertical mill, boring machine or bolt it to a faceplate and bore it on a lathe.



Measure the new bearing for thickness from back of shell to surface of babbit, and do the math to see if you're close. If so, put it together with a plastigage and measure it. You should have .001



If the crank isn't worn, a NOS bearing should work fine. They certainly didn't 'line-bore these things at the factory.

Geoff

Uncle Josh is on track. Years ago I had a '35 Terraplane which had a knock in the centre main. I dropped the bearing cap and there was a loose lump of white metal fell out. Luckily I had another engine handy to use the cap off for setting up for boring. I re-metalled the spare shell, and bolted the two caps together, with the correct number of shims in between. An engineer friend set it up in a four-jaw chuck in his lathe, so that he centred on the original shell, and bored it out for me. This lasted for as long as I had the car, and many years later after the car was written off in accident I obtained the motor, and stripped it down, the bearing was still in excellent condition.

Geoff.

Park_W

Maybe a bit of amplification about line boring would be useful here ... it certainly wasn't done at the factory, because the blocks just recently had the bearing caps precision bored/reamed while mounted in the block, so the bores were concentric. But as the block "matures" when in service, stresses in the casting can work out and result in some misalignment of the main bearing bores. One never knows whether, in a given block, the misalignment is enough to cause problems or not, and it's difficult for the average mechanic to measure it accurately. So the conventional approach has been to install "semi-finished" inserts and have them line bored to ensure the bores are concentric. Of course some blocks haven't become misaligned enough to present a problem, so one can just put an insert of the right size in and all's well. But one also encounter blocks like the one in my' '47 C8 now, which wasn't line bored when rebuilt some years ago, and has enough misalignment that the crankshaft is locked up if the main bearings are adjusted to anything closer than .004.

[Deleted User]

Hi Todd,--- Please advise who the line borer is in your area? Thanks. Cliff Minard.