I just bought a new block and for reasons out of my control I could not get the correct main caps to the machine shop so they could measure the main bores for me. The block does not have letters etched into it so I dont have any way to know what bearings to order without manually measuring...

I may take the block to another machine shop once i have the main caps but I'd like to be prepared to do it myself otherwise. I will be buying an inside mic for the job, just have a few simple questions and want to know if you all have any tips...

Torque the caps to spec and measure? does the mic have to be .0001" graduation or will .001" do the job?

thanks!

 

If your going to mic it then you need an inside and outside mic (for the crank journals). I think .0005" accuracy is good enough and pretty common too.

However most people just plastigauge the bearing clearances. Use whatever bearings you have or a set of standard ACLs as a starting point.

 

i've got an od mic but unfortunately i dont have any bearings to start with... i'm going to try and go off these measurements since it seems to be the only option.

thanks!

 

Yea you have the right idea. Torque them down and subtract the crank journal diamter from the main cap diameter in 45 degree increments to get an average. You will then see the clearence left.

Take that clearence and subtract out the clearence needed after the bearing is installed and you will have the thickness of the bearing needed.

Jeff Evans has a chart on his website that has the thickness of all the bearing colors, if you are using OEM bearings. You can then order than, stick em in and plastigauge to double check.

This is the information I have gathered from building my motor. I am not claiming it is 100% correct as I have not completed my motor yet, but it seems to make sense to me. I am sure some other will chime in here in a little while.