We moved the bell housing and re-did the measurements. This is what we came up with. You can see we got it down to 0.003 TIR. This time I was smarter and remembered to write down any negative numbers...but we didn't have any as all readings turned out to be on the positive side of the indicator this time.
There was a great question asked on the other thread and here is some supplemental material.
"I would like to know what sandwich used to drill out the dowel pin holes with, since I believe they need to be accurate holes. Did he use a drill press or just a hand drill. Are these holes real critical. And do you weld the dowel pin bushings in after your final centering of the bell housing. I assume that once this has been done the first time that removing the bell housing to replace clutch etc. will be centered the next time it is put back on the engine."
We actually used a mill, but a drill press (or even by hand) would be fine as they do not need to be too accurate.
Yes, you must weld the dowel pin bushings AFTER the final centering. It can get very tricky as the bell housing will move around while you are tightening it. It can really try your patience. Yes, the bell housing will stay aligned forever...well, at least until someone line bores the crank journals which is what screws up the alignment in the first place--especially watch out for original blocks.
We just used an standard 1 1/16 drill. The bushings are 1 inch in diameter. They do not need to be that accurate because they have 0.030 inches (1/32 inch) of clearance around the hole anyway. You will weld in the slight gap.
I should mention here, there are offset dowel pins that are available from Lakewood. We have found that very few engines are within the adjustability of the pins, so we just drill holes and use the weld bushings. I must say, however, that lately the engines have been better than they ever have been before. So, there is a very good possibility you could just use the pins and not have to weld. I know that would be a better option for many of you guys.
That said, the dowels in the engine block can be almost impossible to remove. When they are particular pigs, we cut them off flush with the block, drill a 1/4 inch hole in them (the dowels are 1/2 inch in diameter) and then weld the hole up. The combination of heat and shrinkage allows you to pull the pin out. (Welding creates heat which expands the metal. When you weld it up, the metal cools off and shrinks--way more than you think it would.) Usually, the dowel will just fall out. If it is still stuck, we weld a bolt on to the cut off dowel and then pull it out. Some can really try your patience (and vocabulary).