Join Date: Sep 1999
Location: Vancouver, Washingon
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Re: Should a newly installed crank be tight?
I agree, the joint between the main cap and block should be seamless. I've had some blocks that I was able to catch a finger nail on, but the crank would turn freely. I would not use a block that had a less than perfect seamless fit for a daily driver. If it was an engine that was for weekend fun, that would be a different decision all together. I will say that getting a crankshaft with all the correct bearing clearances is no doubt the most important part of the engine building process. I don't mean to say that the other critical engine part clearances are not important. It's just that for long engine life and good oil pressure the crank has to be correct with all the clearances. If a piston is off by plus .001", the engine will run and most likely not even smoke out the exhaust. If a main journal is off by plus .001" the engine just lost 15 PSI of oil pressure, if a main journal is minus .001" there's a very good chance of spinning out a bearing. I usually shoot for .0018" clearance on main bearing, then after a few thousand miles, the clearance will grow to about .002" which is going to help make an engine last a very long time with regular oil changes.