Bearing clearance issues

[Touchdown038]

So today I decided to check the rod bearing clearances with Plastigauge while the crank was out of the engine (before I get it put together) and, well, it wasn't what I expect. I did the first and fourth rods and on each one I got around .003 for oil clearance. Isn't that a bit much for stock? The machine shop declared the journals to fit standard size bearings, could they be wrong?

Also, is it normal (after torquing the rod nuts to spec) for the bearing caps to be difficult to pull off? I had to tap the studs with a wooden dowel and hammer to get them loose. Could that have messed with the reading at all?

[DAEDALUS]

If you're using plastigauge under the caps, wouldn't the actual oil clearance be 1/2 what the plastigauge reads because the journal will be biased to the far wall (not centered)? So actual oil clearance is .0015 around the entire bearing? That's what I've always thought, but I'm not certain.

[Touchdown038]

I'm not quite sure what you mean by biased to the far wall. Can you explain?

[Touchdown038]

Bump... anybody else have a say?

Anything helps.

[180fan]

Ask the machinist to check the sizing on the journals and on the main caps. 0.003 sounds a bit big, Nissan's have very small clearances with bearings. Either that or get a micrometer to measure it. I forget which one I used but for the bottom end, it's good to have the 0-1", 1-2", and 2-3" (3-4" if you're reusing your stock pistons) micrometers as well as the inside versions of the 0-1" and 1-2". The bearing caps being difficult to pull off, yes that's pretty normal. Make sure you didn't damage the block when they were going down though, since they're being held to the block at the sides. I use some motor oil to make sure they go down a bit more smoothly and evenly. You might want to do the same (at the sides of the caps where it meets the block).

[Red coupe]

If the crank is just resting in the journal the bottom side of the crank will be resting against the block. its not centered in the bore until its lifted by the film of oil that lubricated it. Im with DAEDALUS your clearance is 1.5 If you want Mic. the crank and get a telescoping gage and check the bore. (Bore-Diameter of crank)/2= clearance

Like Daedalus said its important to remember your reading the clearance with the crank althe way to one side...like this (O ) (notice 2 spaces on one side) when it is like this during operation ( O )(with crank centered the difference measured before is split on either side)

[Touchdown038]

Thanks guys, especially red coupe for explaining that, .0015 sounds a lot better.

Also I think that it could be that the plastigage is binding to both the journal and the cap when it's being compressed. It did on the main journals while I did it today, so maybe that could have something to do with it as well.