Thrust clearance tooo tight?

[PHANTASM]

i measure .002 to almost .003

steel crank motor with billet center mains.

just want to be safe

 

[Chuck Leeper]

How did you go about bedding the bearings, prior to measurement?
What was the method you used to take the measurement?

 

[PHANTASM]

How did you go about bedding the bearings, prior to measurement?
What was the method you used to take the measurement?

installed bearings and seated caps into register, snugged them, then pryed crank forward-rearward-forward then torqued to spec.

installed micrometer set up on front of crank snout to measure.

 

[turbofabricator]

That clearance is a bit too tight. Easiest way to fix it is to sand the FRONT thrust surface with 320 grit sand paper on a flat piece of glass or granite table. Some table saws or band saws have a machined surface you use, too. The rear surface takes all the load, that's why you sand the front side. Use a figure eight pattern when sanding and do your best to keep it flat. Measure the thickness with a micrometer or dial caliper so you know how much you are removing. Make both halves exactly the same. I have to do that frequently especially with the forged cranks. Better too tight than too loose, though. At least its fixable with out buying a .010 oversized thrust and matching the crank to fit.

 

[coach]

I just measured mine in the car yesterday. It was about 0.0045-0.0055. I thought I had an issue, so I was asked to check it to rule it out. My engine has 24,000 on it, so I think that is pretty good.

:biggrin:

 

[11.20n1320]

What brand of bearings did you use?

 

[joey316g]

Sanding is good advice. Ive had to do this with aftermarket steels numerous times. One last tip before sanding...while snugged up, get a bronze or brass punch and give the crank a light shot with a hammer in the reverse and then foward before locking it forward with prybar and torquing....sometimes prying isnt enough pressure to move/align the bearings. If still a no go, one last thing is if you sand them, put a little oil on the sandpaper...it will give a nicer finish.

 

[PHANTASM]

what brand of bearings did you use?

fm 107m i believe

 

[Tweeked6]

There is no good way of saying this, but before you go sanding. Measure the crank thrust width and measure the bearing. With steel main caps there could be two major issues. One being that the studs are binding in the holes of the main caps. The cure for that is drill them out. Second that cap may not be square in the block. That means that the cap was machined wrong or the machinist did not install correctly. If you measure everything first you may find that there are more issues than meets the eye. If the cap is crooked in any way you WILL have thrust bearing issues.

 

[turbofabricator]

There is no good way of saying this, but before you go sanding. Measure the crank thrust width and measure the bearing. With steel main caps there could be two major issues. One being that the studs are binding in the holes of the main caps. The cure for that is drill them out. Second that cap may not be square in the block. That means that the cap was machined wrong or the machinist did not install correctly. If you measure everything first you may find that there are more issues than meets the eye. If the cap is crooked in any way you WILL have thrust bearing issues.

This is an accurate post for sure. I have seen the main caps installed wrong. Not an easy proceedure. Most of the time the cap needs to have the holes elongated to get proper alignment. Pull the caps, crank, and thrust bearings. Check the alignment between the cap and the block. Look closely for a step between the two. Torque the cap to full value and see if it aligns correctly. I SMACK the crank backwards, then forward with a "Whicita Whacker" aka 3lb. dead blow mallet. then torque the studs.

 

[BadAssGN]

There is sound advice here, but before I'd start any sanding, try removing the main cap and resetting everything, if the cap was too snug when you pryed it, you may not have it set right.

use the Whatchamacallit wacker method