bearing clearance, oil pump questions

[austinsailor]

My 48 B1B runs fine, but after 10 or 15 miles at highway speed (OK, 45 mph!) the oil pressure drops. Down to about 20 at speed, nearly zero at idle. When cold its fine - over 40 at speed, well over 20 at idle.

In my past experience, that means either mains or oil pump is worn.

I just checked the two middle mains and one rod, they all show about .003 with plastigauge. Bearings are standard, I suspect they are the ones the factory put in.

I can't seem to find a set of feeler gauges in my shop and will head to town to get some in a minute, but I'd estimate there is about .005 or so, maybe just a bit more, backlash on the gears of the oil pump with the cover off.

Somewhere I have a new oil pump for a '40 Dodge car, and I expect I can just change it out to solve the pump problem - assuming there is one. I'm tempted to just get some .001 under bearings all around and put them in.

Shaft looks good and clean on the bearings I have off.

Any thoughts?

[JBNeal]

thar's a nick on yer oil pressure relief valve...clean that all up, ya should be good to go.

Edited December 7, 2010 by JBNeal
added photographic evidence

[austinsailor]

Good thought. I'll go check it right now.

[austinsailor]

Well, the oil pressure relief appears to be in fine shape.

However, the oil pump vanes show pitting in addition to play. I opened up my new pump, which has no measurable play. It looks to be the correct pump, part no. 601269. It is in my parts book for my 40 dodge car, I have no manual for the truck, so I'll just have to try it.

First, I have to spend some time cleaning it up. It was still sealed in paper and cosmoline, quite a mess.

I'm still open to ideas, but I see no reason not to replace the pump. I'll probably button the pan back up and try it.

Added: Looking at Bernbaum's site, and Epay, it looks like if it's a flathead 6, it fits.

Edited December 7, 2010 by austinsailor

[austinsailor]

To finish off my own post, I just fired her up with a new oil pump. Didn't run it long enough to get it hot (it's about 20 degrees F outside) but it has much better oil pressure at idle now than it did, so I think I've improved things a lot.

Now I need another new oil pump on the shelf for next time.