Measuring Main/Rod Clearance With Bore Gauge?

I do it both ways. Can't hurt. Always comes out bigger with shells in place for me. Like Dan said set the bore gauge so there is very little tension, like the end of its travel while having enough to cover your clearance range.

Bearing shells have eccentricity and are taper at the parting line to allow for mismatching of parts slightly as I understand it. Clearance out there is usually high and most say not to bother checking. I record it while I'm in there. Good info for future reference and you never you know when you might catch something. All part of balance and blue printing

Hope to have the block back this weekend from the re-hone. As soon as start to get my numbers together I'll post them up to make sure there are no red flags. Thanks Guys.

451Mopar; Do you have the specs for a 400 handy? I'm building a 451 as well.

Sure Greg. Any added tips are highly welcome. I'm trying to step up from the street builds with plastigage to a well documented motor for the race car so I can hopefully track any problems before it grenades. As I get a little older I'm finding more enjoyment from this. Good reason to buy more tools as well.

Make sure that your new mikes are graduated .0001". You say you already have a dial bore guage, hopefully it is also .0001".
The .001 mikes and the .0005 DBG's leave you with the need for guesswork.

Have fun!

The new mic is .0001 & the bore gauge is .0005 . Hopefully that will work. I never thought about bearings when I originally bought the gauge. I could probably get a .0001 gauge if really needed.

I don't like using a bore guage in the bearings as it almost allways scratches the bearing. I have a ball micrometer, and measure the thickness of each bearing shell. Most of the time the bearings vary, as much as .0002". Then measure the crank, all journals, two spots on the rods, center of where each bearing rides. A lot of times there is .0001/.0002 taper. I have never seen a crank where all jrnls measure all the same. The better ones are within .0001"/.0002". Then use a bore gauge to check main bores and each rod. Write all your measurements in a notebook. After you have all your measurements you can find the clearances and fine tune them, a lot of times, by strategically placing the thick and thin bearings. On the rods you can pick and choose which journal and thick or thin bearing, to place each rod. you can equalize the clearances a lot better using this method.

On the mains, if you have .0002" variance in the bores and .0002" variance on the jrnls. on the crank, and .0002 variance on bearing, and you end up with the smallest bore with the biggest jrnl on crank, you can put the thinner shell in that spot. This is more important if running tighter clearances. Of course the #3 bearing on a BBM and #3 and #5 on SBM you can't be selective.

Also if you have the block align honed to the low side, BB Mopar example, 2.9425" and the crank ground to the high side, 2.7505", minus your undersize, and the bearings near the max wall thickness, which they almost allways are for the Mopar aplications, you will have only .0002 clearance. Similar problem on the rods. Almost allways when I have a Chrysler crank reground it is .011"/ .0115" undersize, not .010. Now a days I usually order the bearings first and measure the thickness of each bearing, and then give the crank grinder the size I want the jrnls.

A engine a little to tight can have big problems, an engine a little to loose will run its a$$ off and live.

Wow. That is alot of work. But If you want it to stand on the bumper & live I'm sure that's the level of detail it takes. I may have to invest in a ball mic as well. Thanks for the detailed explanation. I appreciate it.