Main bearing spacers and oil clearance questions

[Dan Timberlake]

Before Plasti-gage Federal Mogul used to sell a set of calibrated sheet shims in various thicknesses to test bearing clearance as described above by installing between crank and bearing insert. I do not recall if they were metal or maybe plastic film.

[Warp Speed]

BillK, put the feeler Guage between the journal and bearing or between the cap and bearing?

Between the crank and the bearing. I know it looks crude and I cant remember who showed it to me but it is a great way for DIY guys to check for an approximate clearance if they dont have the correct tools. I have tried it on a few and found it pretty darn accurate. Naturally you can only do the first main but it can help verify your other checking methods. If you can tighten the cap down on a .002 and it slides out you know you have at least .002" clearance. If you use a .003 and it locks up, guess what . . . you dont have .003

The narrow feeler guage method is a direct measurement and extremely accurate.
Your guage thickness can obviously be checked with a micrometer.
I use it for piston to bore clearance in bike engines.

And people are worried about bore gauge contacts marking bearings! Lol

[Bob Hollinshead]

.003" with .004" on #5 is no problem and you will have zero issues. Just curious why you dont have the oil pump bolted on when checking. Bolt it on and watch the cap move. Surprised none of the other experts didn't notice.

Thanks for the reminder on the oil pump! I know you are supposed to have it on but I always forget! I'm far from being a pro engine builder.

[AA Performance]

.003" with .004" on #5 is no problem and you will have zero issues. Just curious why you dont have the oil pump bolted on when checking. Bolt it on and watch the cap move. Surprised none of the other experts didn't notice.

With those clearances......does it really matter?!? Lol

Not really with .004" on the rear, but he didn't know he had that much untill he measured it. I bolt on the pump before any measuring.