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.
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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.
jeepsr4ever
I cant remember the last time I saw a plastic plug in the bottom of a pickup...maybe the last year was 1974 I cant remember but if you were running fine then it dropped off I wouldnt guess the pickup. I would guess a cam bearing walked out on you, filter stuck, pressure relief stuck, blown out gasket on the timing cover. I would measure from the bottom of the block to the end of the pickup and then from the top lip of the pan to the bottom of the pan. This will tell you if your pickup is not screwed in all the way.
TKFireman
I pulled the oil pan again this morning. From the bottom of the block to the bottom of the pick-up is 7 1/4" From the top of the pan to the bottom of the pan is 7 5/16" Only 1/16" difference. Of course that is with no gasket in there. That could definitely be the culprit. So I went to unscrew the pick-up and found that the headers and the passenger side motor mount are in the way. So now I can either support the engine, remove that motor mount and header, install new pick-up, with spacer, re-install oil pan and hope that fixes it, or I can go ahead and pull the engine and strip it down on a engine stand and check everything, all the way to getting new high pressure cam bearings installed. That's lots of work, but only the cost of new gaskets and cam bearings. This is the first engine I have ever built and would appreciate any suggestions on where to go from here.
jeepsr4ever
Did you lube the threads on the pickup tube before installing it? Can you tighten it 2 more turns?
TKFireman
I used thread sealant on the threads, and if I remember correctly, I screwed it in until it got tight. I may can tighten it, but again, I'll have to remove the pass. motor mount and header to do so.
TKFireman
Is it possible it sucked to the pan and actually bent the tube slightly and lost some clearance? I put modeling clay on it and sat the pan in place to test the fit when I was first assembling it, seems like I had plenty of clearance, however I don't recall the exact amount.
tufcj
I'd just MIG a nut to it. Be very careful not to get any spatter in the engine or pickup. Normal engine vibration could let it drop if it was marginal to begin with.
Bob
tufcj
tufcj
Another thing I thought of is that I've seen the tube on the pickup stress crack at the bends. It will suck air thru the crack. Inspect the tube carefully.
Bob
tufcj
TKFireman
I'll inspect it, try to make sure its sealed to the block,and make a spacer of some sort for it. Think I might order the steel midplate set with thin gaskets too, seems like a good price for extra insurance, what does the oil filter bypass plug do for your engine?
tufcj
The oil filter bypass is just supposed to open if the filter is constricted enough that oil can't pass thru it. Dirty filter, bad media, etc. It does let unfiltered oil back into the engine. That's why they eliminated it sometime in the 80's. Later oil filters adapters don't even have the passage machined.
I use the Bulltear midplate in all my builds. Cheap insurance.
Bob
tufcj
TKFireman
I'll order the midplate, .007 gasket and bypass plug, any other upgrades from Bulltear recommended while I'm at it? I assume I get some plasti-gauge and try the .007 and .085 gaskets to see which has the best clearance? What is the optimum clearance? It says these gaskets go in dry, with no sealant whatsoever, is that right?
