Forum » General Engine Building Discussion » Aftermarket Rod Manufacturer Clearance or Factory Service Manual Clearance for Rod Big End Bearing Clearance?

Aftermarket Rod Manufacturer Clearance or Factory Service Manual Clearance for Rod Big End Bearing Clearance?

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I'm starting down the path of doing my first engine build, and I can't find a clear answer on if I should use the Rod Bearing Clearances listed in the factory service manual or those provided with the aftermarket rods that I bought.

The service manual (Mk3 Focus RS) calls for 0.0011-0.0020", while the aftermarket rods (Manley H-Beam ARP2000) call for 0.002-0.003".

Going off the general rule of thumb of 0.00075-0.0010" per inch of shaft diameter I end up with 0.0015-0.0020", which is more in line with the factory specs, and is what I am currently going to plan on going with.

Thanks for any and all insight!

I think ALL Manley rods say to target 0.002 to 0.003 clearance. Its just the generic crap they print out and put in the box.

Manley also seam to always target the smallest end of tolerance for the rod big end bore (and in some instances, even tighter than allowable tolerance). So unless you plan on polishing about 0.002 off your crank rod journals. Or honing the rod big end bore out larger by about the same. Or using bearings with additional clearance, then your not likely to get anywhere near the 0.002 to 0.003 they say right off the bat.

You should measure the big end bore in your Manley rods and see what it is. I bet it will be pretty much on the tighest end of allowable tolerance.

I always start by using the OE manufacturer's recommendations for oil clearance unless there is a very good reason to alter them. If you're making significantly more power or running to a much higher rev limit than stock then it's wise to aim for the top end of the clearance range.