Hey there....


My 390 has had bad oil pressure since i got it. so i decided to change the oil pump today. got er done and when i started in up it went right to 60 lbs. then i drove to work it dropped to like 20 while i was going down the highway. then came back up. it runs at like 5 lbs at an idle. do you think the gear on the distributer could be stripped out of what. somethings not right that the pressure is going up and down.

 

That happen to me once it was the hose(cracked) it would sometimes give accurate and sometimes not....prolly not it ....just a thought ps( doesn engine run diffrent)?

 

mudin man, do you mean the line to the mechanical gauge could be craked?

 

If your bearing clearances are out due to a worn motor, changing the oil pump won't do much for you. Although 5lbs of pressure at idle seems scary, it's not unusual for a higher mileage engine. A good rule of thumb is about 10psi for each 1000rpm.

 

It deffininetly sounds like a worn borttom end to me. When the oil warms up it runs out of the loose main and rod bearing more easily. The low pressure isn't as big a worry as the pounding the bottom end may be takeing.

 

do you guys think that it could be just that the gear on the distributer could be stripped, causing the oil pump to turn sometimes but not sometimes? Also can i seal that oil pump with high heat silicon unstead of that expensive gasket?

 

Is it making noise? Does your pressure come back up to that happy 60 psi? If its running smooth at 5 psi its probably your gauge(or your line). If your distributor gear was wiped out, your timing would be changing constantly(basicly, it wouldn't run). What expensive gasket? I do not recommend you put your oil pump together with RTV. Its an over-use of RTV, and I've seen that kill many-a-motor. Oil pumps in paticular, are engineered, machined, and designed with the gaskets in mind only. Check the hex socket in the bottom of your distibutor and the oil pump drive drive shaft especially, they may be worn. When ever I replace an oil pump on an FE I always replace the drive shaft. The ARP ones run about 20.00, are made of a stronger steel, are almost twice as thick, and will fit in any FE with a 1/4" drive shaft. Its a secure feeling having one of those! One common problem on FE oil pumps is the releif valve sticks, but the oil pressure wouldn't be going up and down. Hope this helps

 

I once had a 66-352 that was so worn out I would loose all oil pressure when ever I pushed in the clutch. It even had the death rattle when I first started it up. I nursed that old girl around for 10,000 miles. Then my brother got it stuck in the mud and was hammering it and killed it. As your experience would prove, replacing an oil pump to solve low oil pressure almost never cures the problem. It may be the bypass as mentioned. Also you may want to try a motorcraft filter, some of the cheaper oil filters have a problem with their innards that can cause strange things to happen.

 

Hey there,
This is an old post of mine, but it still applies!

I just want to say I consider myself myself somewhat of an expert on the low oil pressure FE. My '70 has an original never been rebuilt or touched bottom end 66 mercury 2 barrel 390 with a performer intake (no the intake ports don't line up) and a mystery cam a used timing chain, but better than the original plastic/aluminum thing, new stock valve springs, headers and 2 1/2" flows. I run straight 50 in this thing and napa 1515 filter. I get 40 pounds dead cold. Hot I top out at 23 pounds once I hit about 3500 rpm. Hot idle is 2 pounds if I'm lucky. I idle it at 900 rpm also. Below 900 it gets nothing. This engine has been through the worst hell I could ever wish on engine and it still lives. Before I drove my 70 daily it was a project and I rodded the hell out of it. With the cam it has it will pull hard to 6900 RPM (with a performer & 625 carter?) I've held this thing at valve float in mudholes and snow for witnessed minutes at a time. I skidded 10' chunks of 48" fir out of the woods and I've towed all kinds of heavy stuff. This engine won't die. I drive seattle to portland and back once a week and that's 4 hours at 3000 RPM. I've also ran this engine out of oil several times. One time I noticed my oil pressure getting low so pulled over to add some oil. I lost the valve cover breather on the ground. I was already running late so I threw my last 2 quarts in and figured if it blew up I had an excuse for being late I taped up the breather hole, but that screwed me because the blowby pressure blew the pan gasket out. I did 85-95 MPH for a solid 45 minutes up I-5 with a nice blue-black cloud behind me. I pulled off the freeway with 5 pounds ands my rocker arms locking up. The next time I drove it, I added 5 quarts to a 6 quart pan and started it and it still drives great (with new pan gasket and breather). What I'm trying to say is- disconnect your oil pressure guage and clean up your interior because you don't need it with an FE.


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It's an FE with worn bearings, 5psi at idle is typical. Use only the gasket on the pump and run straight 40wt oil, it will run like that forever.

barry

 

40 w? thats different than 10 40?
do i have to use the oil pan gasket or can i just silicon it? if i have to use the gasket should i put a thin film of silicon on it?

 

Yes, in worn engines a straight weight oil will hold pressure better than a multiweight. You can go either way on the pan gasket, I take it you're having a little trouble underneath there.

Barry

 

well ive done it before with the gasket but this time i forgot the dang thing im in the high school shop with my truck torn apart so i ran down to ace with only 5 buck in hand and all i could get for that was this little bitty tube of high temp silicon so i did it and its leaking like a sive. screw it ill fix it saturday

 

Should have bought a bigger tube.

5 bucks don't go far for sure, sorry to hear about that.

Barry

 

thanks for the advice everybody im gonna pull the gauge out of my parts truck and try it. if that doesnt help im gonna say hell with it and drive for how ever long it drives and not worry about it. "after i fix the darn leak"