At 05:32 PM 4/26/05 -0600, David Gills wrote:
"1961 Elva Courier - Would you happen to know the original ID & OD on a set of main berings I have w/o measuring them? They are marked with a "P&V inscribed in a circle" and have the numbers/letters- 4341 12H62 ....."

I will make the rash assumption that this is a 1600 engine (same crankshaft as the 1500), not the 1622 engine. I was just measuring the inside witdh across three spare main caps here, and I came up with 2.146. I was also measuring the big end bores on my spare set of rods, and come up with 2.021 (on the 3 good ones). That makes good sense, as there is .125 difference between main and rod journal diameter, and presumably the bearing shells might be the same thickness.

All of this got me cranked up to go try out my new dial bore gauge. I bought it for measiring cylinder bores, but it seems to work as well for bearing cradles. It has a dial gauge read out in 0.0005 inch increments. It is easily repeatable to even better accuracy, but is a little tricky to set up for the initial base dimension. It has a range of 2 to 6 inches, and the big ends are just over 2 inches without the bearing shells. I used a 2 inch micrometer for the initial setup to zero the bore gauge. Initial dial caliper measurement makes the big end bore close to 2.020 diameter, so I add a precision .0200 shim (included) to the bore gauge pin to put the dial on zero at 2.020 diameter. Then when measuring the big end bore it shows +.0010 on the dial, so the bore must be very close to 2.021.

For a cross reference check I put the old bearing shells back in the big end, but positioned them so they hang out one side of the cradle about 1/4 inch. Then I torqued up the bolts to make it secure and round out the bearing shells, and proceed to measure the OD of the bearing shells with a dial caliper and with a micrometer. This also comes out to be 2.021 inch, which makes me feel good about use of the dial bore gauge. Then I used both the bore gauge and a dial caliper to measure across the width of the spare main bearing caps (best as possible without being in assembly with the block). Here I get 2.146, which is exactly 0.125 larger than the big end bore.

Additionally I used a micrometer to measured the thickess of the un-worn end of a big end bearing shell (several of them). It's a little tricky measuring the slightly curved surfaces, but fairly accurate if only overlapping the micrometer a small amount onto the surfaces. Here I measure 0.072 inch for the thickness (radial thickness of the bearing shell).

For my bore measurements with the dial gauge I feel confident with all the numbers being accurate to within +/-0.0010". Additionally, the dial bore gauge is easily repeatable to within 0.0005 inch total range, so it is very easy to tell if the bore is out of round.

Now the stack up of dimensions looks like this.
Pay attention to min and max and how they add up.

OD 1.8759 to 1.8764 Crank pin standard diameter spec.
add 0.0020 to 0.0005 Oil clearance (on the diameter)
total 1.8779 to 1.8769 Bearing bore spec (new and unworn)

To this I arbitrarily add 0.0001 just to round it off, giving:
total 1.8780 to 1.8770 Bearing bore spec (new and unworn)
add 0.0715 or 0.0720 Bearing shell thickness (one side)
add 0.0715 or 0.0720 Bearing shell thickness (second side)

total 2.0210 2.0210 OD of bearing shell or ID of big end bore.
Knock off the trailing zero, because my measurements aren't the accurate, and you get
total 2.021 2.021 OD of bearing shell or ID of big end bore.

I'm damn sure this is correct, but I don't know what the 4th decimal digit should be.

For the main bearings add 0.125 to all diameters.
Change the journal OD slightly to account for differences in oil clearance.
Reduce journal OD in 0.010 increments for regrinds.
Increase bearing shell thickness in 0.005 increments to account for regrinds.

One thing that bothers me a little is the book specs for oil clearnace in the 1500 rod journals. By the book it could be as little as 0.0001, which I think it impossible as it would not allow for any oil flow for cooling the bearings, and friction would make them promptly overheat and melt the white metal. The 1600 spec is .0010 to .0025, which is reasonable. I don't know why there would be a difference, because the 1500/1600 cranks are the same part number. Possibly the later dimensions superceed the earlier ones in production, so any replacement part would have the later dimensions.