Piston clearance

You should use a micrometer to check piston clearances. Mic the piston with an outside mic (Ross probably has a specific location to mic the piston at too). Mic the cylinder with an inside mic then set the inside mic into the outside mic and check the reading. Inside mics have inherent error built in. Checking the reading with the outside mic eliminates the error.

I currently run 0.004" clearanceon a set of TRW forgings, and this works well enough that I passed CA smog testing with the engine warm. I wouldn't second-guess the mfgrs. Incidently, pistons are not round so mic-ing them is extremely difficult. The skirts are ground barrel-shaped starting just below the rings, so if you must, the micrometer should be below the ring pack, at 90 degrees to the wristpin holes. This area is the closest to cylindrical. Feeler gauges can be used but it takes experience to gauge the drag on a blade, plus, if you insert it too far, you intersect the skirts which are always larger in dia than the ring lands. I've tried it and it only confuses me.

I know where to mic them, instructions were included. I slid them into the bore and tried the feeler gauge method they are a little tight. I used the micrometer to measure bore and pistons .2" above the bottom of skirt and did the math, they're loose. What's up? I tend to believe the feeler guage and not my micrometers because the feeler guage is consistently binding at 0.003->0.035" at the bottom of the skirt where it should be tightest. This leaves me with just a bit to hone. I get 0.006-.007 by mic/math method.

I'd get some professional help to measure this. At 0.006" clearance, brand-new rings won't last long before youll be pumping oil overboard at a rapid rate. Also note that cylinders wear to a taper, so unless the engine has been recently honed straight, preferably with a torque plate, you'll get a different measurement close to the top of a given bore where wear is greatest, and half-way down where wear is much less.Another way that works on blocks is to use a piston to shove one of your new rings down the bore about an inch, then use feeler gauges to measure the end gap. Ring length x pi = bore diameter. Try it again 3" down; if theres taper in the bore, the readings will be different. The piston is used to guarantee the ring is square in the bore. Surprisingly, I found it takes some practice to get the feel for accurately measuring things with either inside or outside micrometers. Once things are to a professionals liking, try your mic's again, until you get the same answers he did, with his mics. This will quickly give you the "feel" & is cheap instruction IMHO, and does'nt delay assembly much. Note there are no trophies for fast assembly of an engine, only for correct assembly. It takes pro Winston Cup builders over a week to assemble a race engine. Take your time.

I haven't touched the motor yet until I can be absolutely sure about this. I have a friend who has a dial bore guage and he has 30 years experience building engines. What luck to run into him again. I'm with you Jack.