Bearing clearances

[LJDB 103]

I was given a vg rebuilt 84da that had chew up a camshaft. I pulled it down and checked everything out and it has done very little work, pistons and bores like new. Upon putting it back together I thought I'd check out the bearing clearances. So the clearances seem alittle tight. Bearings are .010 oversize and mains measure using plastigauge between .0015 and .002 and rods around the same maybe alittle more.

Will this be a problem or do I just use thin oil? Is there away to increase clearance? It seems alittle tight to turn over by hand but its smooth, I have another healthy xflow here with good clearances that turns over easier.

I suspect being a bulletproof xflow it should be ok but engine building can be a black art.

[bear351c 10,270]

002" thou sounds about right. When you say 'tight' ...do you mean wont turn over without a massive bit of pipe on the socket.?

 

Crankshafts actually run in a thin smear of oil, never touching the bearing surface when running, but after sitting idle, the crank will rest on the bearing shells.

This will make it harder to turn.  Did you put startup lube or oil on the shells/rings/crank/cam, when reassembled?

 

Bit hard to diagnose over the 'net.

[LJDB 103]

Yeah I lubed up the bearings before reassembling. I turns over fine just not sure if .0015 is too tight for the mains as most recommend .001 per 1" shaft diameter making a xflow spec around .0025. Im just thinking if its an issue, it would be better to sort it out now while its apart.

[SPArKy_Dave 8,869]

I've got a Crossy here with 300,000km, that has 6thou on the big ends.

It still ran fine, with no knocks.

I measured it with plastigauge, out of interest.

 

I'd feel comfortable with 3thou personally.