Engine Rebuild Kit- Bearing Sizes?


Founding Member
Jun 9, 2002
I about to order ( and drop a big wad of $$$ :( ) on an engine kit because Ford decided to put Hyper(whatever-you-call-it) pistons in my '93 Mustang GT and i was crazy enough, 10+ years ago, to put the parts listed in my signature.. not including the suspension! I popped a gasket and need new piston rings since i've been having oil related issues for the longest time, so it's about time to address the piston issue.

I'm ordering a 0.030' bore engine kit and have options regarding the size of the Main Bearing Undersize (Standard ; .010" ; .020") & Rod Bearing Undersize (Standard ; .010" ; .020"].

What size should i be getting?
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Bearing kits are damn expensive.
I suggest you get the rotating assembly out and inspected prior to buying bearings for it.
You or your machinist will then know what you need. It may be std, oversize or a new crank... you just won't know until it's in your hands, cleaned and mic'd.
Normally for a local rebuild, you have the crank cleaned and measured to determine if it can be reused with standard size bearings, or if it must be turned and undersized bearings are needed.

You can order a specific undersize bearing, and hope the crank will be ok at that size.

Main bearing sets are cheap, $35 or so. I would just wait until the crank was miked and checked.

If you buy an entire rotating assembly, or a crank kit, it will come already machined with matching bearings. Even then you must check the clearances. I have recent experience in this....