Determining 440 bearing sizes?

[polkat]

I bought an apart 440 that was going into a Duster, but the guy sold the car. The crank is very nice and smooth. The old rod bearings are gone, but most of the mains are still there (they look great). On the engine pad is the backwards letter B, which I thought meant .010" undersize journals. However the crank's mains mic out too big for a .010" cut (but a little smaller then standard-which may be caused by my crappy old caliper). The only markings I can find on the bearing shells are on the 3rd main (thrust bearing) which says AT20 P-72 on the upper shell, and AT20 P-43 on the cap shell. There is no apparent taper or out-of-round on the journals.

I am trying to determine what size bearings to buy for this engine. The main journals mic out at between .002"~.005" smaller then the 2.80" standard, yet when I checked them with Plastigauge I got a decent .0025" clearance on all of them (on the old shells). The rod journals mic out at between .008"~.009" smaller then standard, so it seems they may be .010" under. I can't Plastigauge them as I don't have the old shells.

What size to buy??

 

[q-ship]

Calipers are great for semi precision measurements, but can not be used for things like bearing clearances.

You either need to buy a micrometer, or take the crank to a machine shop and have them measure it (free if you're nice).

The letter "B" is most likely irrelevant as the engine has been re-machined, so let a machinist check it and tell you what you have/need.

 

[Meep-Meep]

What he said.

As far as block stampings go, a maltese cross denotes a .010" under size journal from the factory. A diamond means a .005" over sized lifter bore. However, after 40+ yrs one can't be sure the same crank is in that engine.

 

[Cranky]

IF you have a good set of dial calipers, you can get damn close but you need to be very familiar with them to get repeatability but using a mic is better but even with those, you need to acquire the 'feel' to get accurate measurements. And 2.80? Standard main size is 2.750 and 2.375 on the throws. Take the it to an automotive shop and let them mic it....

 

[polkat]

No, the block has not been re-machined as far as I can tell. My mistake about the mains, which should be 2.750" but all my books say 2.380" for the rods. Is it in fact 2.375" for the rods?

 

[Cranky]

2.375....don't know where that .380 number came from but I've seen it before too.