aluminum blocks, bearing clearances and oil viscosity

[philminotti]

When I built my last aluminum block 15 years ago, general consensus was 2.2-2.5 thousandths on the main and rod bearing clearances.  I've been running 15W-50 Gibbs HR-1 oil mainly because it seemed like a good idea at the time.  That was with Crane hydraulic roller lifters as well.

I'm planning on using Morel 5329 short travel hydro roller lifters on my new build, and I found a spec sheet on them that dictates oil no heavier than 5W-40. 

Do any of the experts here think that the bearing clearances need to be tightened up for oil in that range?

[blykins]

For an aluminum block, I run .0020" on the mains with coated bearings and .0020-.0022 on the rods with coated bearings. 

A 5329 will run with 10W30 and I run Valvoline VR1 non-synthetic. 

If you're not going to 7000 rpm, I wouldn't even bother with the short travel lifters.  The 5325's do very well at around 6500-ish.  Dennis Towle launches his wagon with one of my hydraulic roller 390's at 5500 and shifts it at 7000 with 5325's.

[philminotti]

Thanks Brent.  Appreciate your input as always.

[Barry_R]

We run aluminum block mains at .002.  Rods are "normal" at .0027ish.