Ok consider this. I had my 427 built by a reputable FORD 427 Expert with over 20 years of 427 & Cammer experience (lets call him RK). After a dyno and resonable breakin, the first day on the track my
oil pressures started to drop 5 - 10 pounds. I pulled my System One filter and examined the filter and I found debris. I loaded up my car and took it home. The next week I had the "NEW" engine out and on a stand. I checked my main bearings with plasti gauge and they read from .001 - .0015 clearance. Then I checked with my mic and arrived at virtually the same results. I also noticed some wear on a couple of the front main bearings but not bad. I had given this builder specific instructions of the clearances I expected.
I then tore my engine down and took my block, pistons, rods and crank to another Ford engine builder in Tulsa. He confirmed my clearances were far to tight and that my readings from home were spot on correct. As a result of my cautious nature, my new engine is still new and I had the new builder turn my crank and rods to within .0025 and .003 clearances that doesn't seem like much of a difference but to a 427 it makes a world of difference. Additionally, RK had not installed a high volume M-57H
oil pump as I had requested. The whole experience was bad for me and a friend of mine that experienced the same clearance problems. The "Reputable" builder RK had became to big and had given our engine machine work to some of his "Young" machinist to do the machining. Although probably competent Chevy engine builders they didn't have the life experience with a Ford 427.
In summary check and double check everything and use a good engine builder that is familiar with what you are doing. George Gessford, Southern Automotive, Keith Craft and many others that know Fords. I will continue to use plasti gauge but I will also confirm my readings with a mic.
Clois