Join Date: Aug 1998
Location: Waldorf Md. USA
Re: Bearing Clearance Issue
I am going to play the devil. Factory specs for a 1970 Corvette 454 are
Rods : .0012-.0037"
So you are just about in the middle for the mains. Rods "might" be on the tight side but to be honest with you I dont see how you can use plastigage on rod bearings. they move around too much when you torque them. So the rods are probably more clearance than you think. In my opinion .003 is too much for rods anyway.
As far as "which has the clearance" the bearing or the crankshaft, there is a tolerance range for both. There is a full thousandth range on the crank. So if you get a crank that is on the large side of the range and a bearing that is on the thick side of its range you end up with not enough clearance. Exactly what does your crankshaft measure ? How about the bearing.
If your rod journal measures 2.189 then it is right at the small end of the spec and you should have enough clearance. If you want to verify your checking method, put a set of bearings in one rod and torque it together. Then measure the rod journal with your micrometer and lock the mic so it cant move. Take the rod and the micrometer down to your machine shop and ask them to set the gauge on their Sunnen rod machine using your micrometer and measure the rod assembly and tell you what clearance you actually have.
I would do that before ordering more bearings.
Personally I would have no problem running a street engine with the clearances you showed in your first post.
Advanced Automotive Machine
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1971 Heavy Chevy - original owner
1984 Buick Riviera - original owner (Wife's car)
Team Chevelle #100