rod oil clearance

[arlancam509]

has anyone run .005" oil clearance on a 2.375" rod journal successfully?

[RDY4WAR]

I think the better question is why would you want to?

[arlancam509]

let's assume i don't want to and that's why I'm asking.

[RDY4WAR]

You need to fix the clearance. You're not going to have a happy engine with that much clearance. Even Top Fuelers don't run that much clearance with a 70 grade oil. It gets sketchy past ~.0035" as the ability of the oil film, regardless of viscosity, to keep the journal from going too eccentric is greatly diminished. Peak load carrying capacity for a journal bearing is ~.001" per 1" of journal diameter which is why that's the industry standard. I wouldn't even think of trying to make .005" clearance work. I'd be getting the clearance tighter.

[Tom Walker]

Would have to agree, that is too much clearance for that size journal.

[arlancam509]

ordered a new set of rod bearings. not sure how i ended up with the clearance i did with all new parts, but i suppose that is how things are these days.
fingers crossed that the next set are better.

[Dan Timberlake]

how did you determine clearance ?

What were the Journal diameters and housing bores.

[arlancam509]

2.375 journal
2.380 id of bearing snapped into rod and torqued
measured a couple different spots with telescoping gage and mics. double checked with decent calipers. (we are looking for thousandths after all...)
there was a couple tenths here and there, but it was a solid .005 on all.

[fabr]

Not a fan of snap guages. I suggest you buy a piece of plastigauge as a pretty accurate check of what you are seeing.

[af2]

You need to fix the clearance. You're not going to have a happy engine with that much clearance. Even Top Fuelers don't run that much clearance with a 70 grade oil. It gets sketchy past ~.0035" as the ability of the oil film, regardless of viscosity, to keep the journal from going too eccentric is greatly diminished. Peak load carrying capacity for a journal bearing is ~.001" per 1" of journal diameter which is why that's the industry standard. I wouldn't even think of trying to make .005" clearance work. I'd be getting the clearance tighter.

I know of few dozen blown Alky that run .009"..............................

[af2]

You need to fix the clearance. You're not going to have a happy engine with that much clearance. Even Top Fuelers don't run that much clearance with a 70 grade oil. It gets sketchy past ~.0035" as the ability of the oil film, regardless of viscosity, to keep the journal from going too eccentric is greatly diminished. Peak load carrying capacity for a journal bearing is ~.001" per 1" of journal diameter which is why that's the industry standard. I wouldn't even think of trying to make .005" clearance work. I'd be getting the clearance tighter.

I know of few dozen blown Alky that run .009"..............................

And I wouldn't on a steel rod deal,