I have measured my oil clearances for my new motor in 3 different ways.

-Plastigage
-Journal with a mic, bearing shells with a mic, and bearing housing with a bore gage.
-Bearing ID with bearing installed and caps torqued properly.

Plastigage said .004" total so .002" all the way around. That seems fine.

Using properly calibrated and certified mics and bore gage I get numbers that don't add up. (yes everything is clean, calibrated, and tightened properly, measured at the same temp and same respective time)

I mic the crank rod journals (Eagle 4340) they are 2.0992" - 2.0993" across the board. The rod bearings (Clevite H-Series) measure .0627" - .0626" for all 16 halves. If I measure the rod journals themselves (torqued via bolt stretch gage) (Eagle 4340 H-Beam, ARP L-19 Bolts) to .0075" stretch. Set the mic to 2.225" and lock it. Set the zero on the rod bore gage and I measured it. I get 2.2245" - 2.2250". If you add up the numbers...

2.2245
2.0993
-0.1254
---------
-0.0004" on the minimum side

2.2250
2.0992
-0.1252
---------
0.0006" on the high side ... either way it sucks


But If I stick the bearings in the rods, stretch em bolts, set the gage to 2.0993" and measure I get .0018" - .0019" of positive room over 2.0993" zeroed.

I am using the correct mic to measure the bearings, a half spherical pipe mic.
I am allowing pretty much zero of my body heat transfer to the instruments.

In conclusion... what gives?!

 

Better post this in the Advance tech for quicker answers.

-B

 

Yeah that was my initial plan but I don't like it when people immediatly post things in the advanced forum that dont seem too advanced but hey, maybe thats the next step. Thanks.