Enginetech main bearings.

[sloinker]

Putting the crank back in after polishing the journals and used plastigage to check clearances. Everything looked ok except for the #1 main. Looked at the old bearing and compared and didn't notice any visual anomalies. Went ahead and lightly scraped and crocus clothed the #1 main bearing a couple times until the plastigage read within normal. Strange. The markings indicated the shells were the same as the rest. I took another look at the pad and under the B 440 there is a 3 and a 1. Does this mean anything?

 

[R413]

March 1st 1966 machining date is what the 3 1 means on a B 440

 

[fastmark]

Plastigage is not the best for building motors. It has its place but it should not be your sole source of measurement. I’ve built countless engines in the last 50 years. You may have a tight main bore from the factory. The only way you can measure that is with a dial bore gauge. You can’t tell much about a bearing size with your eyes.

 

[sloinker]

Yeah, date code for assembly/machining. I used the search function after I asked the question. The plastigage method was in the literature I am using. I did use a digital caliper initially on the journals bit not the bore gauge. The crank is now as smooth as butter after my intervention. I suppose time will be the test of my machining abilities. Thanks

 

[65-440]

Plastigage is not the best for building motors. It has its place but it should not be your sole source of measurement. I’ve built countless engines in the last 50 years. You may have a tight main bore from the factory. The only way you can measure that is with a dial bore gauge. You can’t tell much about a bearing size with your eyes.

100% spot on. If you're going to build engines you need the tools, or at least borrow from a buddy that does. And write it all down. Although a lot of people just slap their **** together and run the piss out of it !

 

[fastmark]

I’ve found one main journal my original Superbird block has one that was .002 larger than the rest of the notes. I swapped the bearings and even different bearing manufacture and never found a good clearance. The factory had many bearings available to it in various +/- configuration so they could get the desired clearance. Would it have run with .0045 clearance? Probably so. But what if it was the other way and too small like yours? .0005? Probably not. I finally found a crankshaft that was .001 BIGGER than normally acceptable so now I’m good to go all std!

 

[zyzzyx]

Yes, a good dial bore gauge is your best friend. The first thing you have to check is
the bore in the block with the caps torqued down. There is a tolerance on that bore
so if it's on the tight side, the bearing will be tight also. These days bearings are made
to exacting tolerances and they can be mixed and matched. If the tolerances stack up
one way, it's too loose. If they stack up the other way, it's too tight. I recently bought
a Dorcey Dial bore gauge on E-bay that covers crank and rod diameters for about
$200.00 and reads in tenth's of a thousandth. And about plastigage, If you have a set
of aftermarket rods there's no way you can assemble and disasemble them without
disrupting the plastigage to get a good reading.