Lost oil pressure in a fresh build

[TKFireman]

I have a 401 with about 500 miles on a rebuild that had great oil pressure, at idle it was around 60 cold and 20 hot, then one day I cranked it and nothing. Here's the entire story

Engine - '77 401 complete rebuild, I built the engine. .030" over, crank ground .010"/.010" heads resurfaced, deck blocked, new bearings, rotating assembly balanced, new timing cover, new pump, pump housing cover lapped on glass to be perfectly smooth and flat. I checked the pump gear clearances both on the end and side and everything was in spec according to my Haynes manual.

First I checked the mechanical gauge, wound up replacing the line and gauge, no help.

I pulled the oil pan, oil was clean, no shiny specs, nothing in the pick-up, re-installed the pan, pulled the dizzy and tried to prime with a drill, drill turned noticeably easier than when I built the engine, oil pressure went up to around 12 psi on the drill, during the build, the drill got 40+ psi.

I pulled the oil pump cover and oil pump gears. No noticeable wear in the oil pump housing or on the gears, you can see where the gears rubbed the end-plate, but barely and no marks deep enough to feel or catch a finger nail on.

Where do I go from here, pull the pan again and re-inspect the bearings? I have a 304 that had good oil pressure when it was pulled, I could pull the timing cover from it and try it on the 401, but I don't see the point as the pump still looks new. Any suggestions?

[jeepsr4ever]

This will sounds basic but the purple wire didnt fall off the sending unit did it?

[TKFireman]

It has a mechanical oil pressure gauge, new gauge and hose since this started, pump is moving some oil, oil comes out of gauge hose, but not very much.

[jeepsr4ever]

It is possible the filter collapsed or your oil pressure valve stuck open.

[TKFireman]

I thought the same thing, when I re-installed the oil pan, I put fresh oil in it and a new filter. The trap door under the filter was closed and moved freely. I removed the bolt and spring from the pressure by-pass, plunger was all the way down and moved freely, re-installed everything, same result.

[390spirit]

oil line under the intake, if there is one came loose?

one of the galley plugs come out?

its not skipping right? the reason i ask is in my younger days i kinda over reved my 390 and bent a push rod, which in turn let the lifter pop outta the bore. instantly no oil pressure.

[tufcj]

One thing I notice is no spacer in the oil pickup. From the factory, the pickup had a plastic spacer about 1/4" thick in the hole in the pickup (where th oil is running out in the last pic). It kept the pickup from being too close to the bottom of the pan. I've seen the pickup actually suck itself tight to the pan, so no oil will flow. I don't think the spacer is available any more, but I've brazed a 1/4" nut to a couple with good results.

I've also seen the oil pump gear that connects to the distributor spin on the shaft. Something to check.

Bob
tufcj

[390spirit]

i also notice no button on the bottom of your pickup in the last picture, it could be sucking it to the bottom of the pan

[390spirit]

oh man treed^^^^^^^^LOL

[TKFireman]

Thanks guys, I'll pull the oil pan back off, re-inspect everything and see about adding spacer to the pick-up. Would the pick-up suck to the pan while priming with a drill, after having great oil pressure for the first 500 miles? Could I mig weld a nut to the bottom of it, or drill a hole and through bolt it to add a spacer?

The engine still runs great if you fire it up, strong, sounds great, just low oil pressure, too low for the gauge to read at idle, goes up to about 20 psi at 2000 rpm. I did not do the valley oil line mod. This is in an '80 CJ7, not trying to turn high rpms, Melling MTA-1 cam, new stock lifters and rockers. I was also wondering if a oil galley plug cam out, but the only way I know to tell is to pull the timing cover and intake manifold off, was hoping to try all other possibilities before I pull those, but I think I may be running out of options.