[cfmcnc]

Use a dial bore gauge and a outside mic,torque main bearings using correct lube in fasteners,measure crank with mic,set dial bore gauge off of mic to 0 ,then rock dial bore gauge inside bearing and see difference on gauge,this is absolutely the best way to measure bearing clearance,same procedure for rod bearings.BillC.

[ry57pont]

thanks, i was using the snap style then using a mic to measure that, i will find a bore gauge this week, even if i have to buy one.

using the mike and snap it looks like i was at.003 on mains and rods. this was at teardown (about 1500-2000 miles) with the F/M standard bearings. i will post more when i can trust my measurements. -RB

[tininjun67]

what Bill said. don't trust the snap gauge. you can't rock it in the bore like a dial bore gauge.

[455firebird1969]

Originally Posted by ry57pont

thanks, i was using the snap style then using a mic to measure that, i will find a bore gauge this week, even if i have to buy one.

-RB

Summit Racing has what you need, thats where I got mine...

[Goat-Racer]

Be careful of the standard $100 style dial bore gauge. The hard ball on the tip of the anvil and plunger is so small that it can scratch/dig through the soft bearing surface. This will give you a false diameter and therefore a false bearing clearance.

Preferred would be a dial bore gauge with a more gradual radius on the anvil and plunger and a lighter spring pressure behind the plunger. Unfortunately this winds up being alot more expensive.

[tininjun67]

what he said. I bought a starret, which is the best I can afford. I think it was $300?. a local tool and die maker said he stopped selling dial bore gauges because he doesn't trust anything that costs less then 1500 bucks and not made in germany. gee thanks I said.

[ry57pont]

i ended up getting a fowler from enco, has not arrived yet but it was on the cheap end. i do however have a calibration lab here at work so i can have it checked for accuracy once it arrives. - RB

[Goat-Racer]

The accuacy is important, but the DBG is not "measuring" the diameter of the bearing bore, it's only telling you the "difference" in diameter between your zero (crank pin) and the bearing ID. Having a DBG that reads down to ten thousanths is nice too.

The bigger problem is that the tiny litle hard ball at the tip of the anvil and plunger, combined with stiff spring pressure behind the plunger can literally dig a trench in the bearing and give you a false clearance. It's not always much, but if your on the edge, it can bite you. They work fine for measuring the hosing bore in the block itself because the iron is hard enough to not be an issue.
Just be careful.