I have a 1979 F150 with a 502 Stroker formerly a 460 motor. The engine only has about 50 miles on it and overheated pretty bad because of a loose connector for the electric fans. It has been sitting for about a week and the last time I drove it there was a slight knock coming from the engine compartment but only during moderate to hard acceleration. I started it up today and when idling the oil pressure is at about 70 psi, once it warmed up I revved the engine to see if I could detect the knock and the oil pressure went up between 75 and 80 psi, when I let off the accelerator the psi dropped out and the engine died. I repeated this a couple of times to try and figure out the problem and I would like some assistance. I'm not sure what it could be and I don't want to replace everything I think it could be just to realize the solution was simple. I will be putting on a 7 quart oil pan, new pick up tube, and dipstick on shortly. I would rather do everything at once and not have to go through the hassle of dropping the oil pan multiple times. Any assistance is greatly appreciated, and I thank you for your time and advice.

 

How bad is pretty bad. Obviously your still running. Sounds like you fried something But...you should either have pressure or no pressure. Where is your knock? A tick in the liftters or a knock down low in the crank or rods?

 

I was at a solid 250 if not up around 300 degrees. I just bought the truck a few weeks ago and didn't realize the temperature was reading on an aftermarket gauge that was mounted to the bottom of the dash.

It sounds like the knock is in the lower side of the engine, but I can barely hear it over my exhaust. It only happens during acceleration not all the time or even when the engine is revved up. I talked to a mechanic I know and he said I probably fried at least one crankshaft/main bearing.

 

One other question...I was going to put the new pan on last week but found I had to get a pick up tube that was compatible with the new pan. Is there any way to tell if the bearings or anything else have gone bad by looking at them, or would I have to pull the engine and take it apart?

 

If you have an auto trans, any/all aftermarket rear sump oil pans will butt right up against the bell housing making it impossible to get at the torque converter studs, something the don't tell you about in their description. Who wants to drop their pan to separete the motor and trans every time ? I had one and got rid of it the first time I had to pull the motor.

 

Yeah. Sounds like a fried lower bearing to me.

 

It has to be a lower bearing. I started it up today and crawled underneath it and heard some noise from the underside of the engine. Thanks for the help.

 

When you have the pan off, you can rotate the engine by hand and wrench with plugs out and one at a time, check rod bearings by dealing with one cap at a time.

You can check mains one at a time as well and not have to rotate the engine.

If you find that all crank jornals are still OK but a bearing insert looks bad, I'ld likely replace all .... again one at a time.

To find sizes, hope they are stamped on back side or if Ford bearings, mic the thickness of the shell over at side near parting lines. A machine shop has a book to convert the results to stnd or undersizes.

 

After talking to a mechanic I that works at the same place I do I have a couple questions. Oil pressure doesn't matter as much as volume, but what is the correlation between psi and how much oil is being pumped? I was also wondering if an engine will run without oil pressure? Lastly I would like to know if it is possible that the oil is staying on the topside of the engine and not coming back to the pan fast enough, which in turn drops the oil pressure due to lack of oil and causing the main bearings to squeal because they aren't getting enough oil either? Any help is appreciated, I thought I was done with this problem but formulated a few questions over the weekend.

 

So after work today I went out to fiddle around and see if there might be some other problem(s) that would cause the truck to die. I have white smoke coming out of the exhaust pipe and it seems to be running pretty lean, but that might just be that I had my face right up on the pipe. Once the engine died it sounded like the air cans for dusting your computer was being let off. It stopped before I could get a good trace on it, but settled for the carburetor. When I took off the air filter there was cool whit smoke coming from 2 of the 4 barrels. Just wondering If that means my engine is completely messed up. Could there be a correlation or is it possible that the guy that rebuilt the engine didn't properly set it up to be a stroker engine?

I guess my best bet is to pull the engine and rebuild. Thanks in advance for any help that you may be able to offer.

 

I recently had the same problem with oil pressure. I was replacing my rear main seal and had to remove the oil pump to do so. When I replaced the oil pump the rod that is supposed to be stuck into the distributor came down with the pump. (I did not know this then) When I put the pump back up in the rod missed the distributor. After I had everything back together and started the truck it was knocking up top and I had no oil pressure. (so yes it will run without oil pressure but is very bad for it). We thought it was the bearings, but thankfully my neighbor mechanic asked me about the oil pump and I didn't remember putting the rod up into the distributor. So I ripped it all back apart and that was the problem.
If I were you I would make sure its not your oil pump or distributor first then go from there.
If you are dropping the oil pan check the rear main while its down so you don't have to do it all again. Also, don't get an after market oil pan if you can help it they are a hassle like they said above.
Hope I helped.

 

Oil pressure is determined by a relief spring which will maintain a set pressure unless there is insufficient resistance in relation to supply. Drop resistance by opening the tap like with worn bearings and the pump can't keep up, oil pressure drops. Keep enough supply to handle the opened up tap with a bigger pump and you can keep the pressure up even with loose clearances.

A high pressure oil pump usually has standard volume potential but comes with a stiffer preload on the relief spring so that if bearings and clearences are tight enough, it will maintain the elevated pressures .... but if clearences open up, the pump still pumping normal volume can't maintain the higher pressure.

A high volume pump usually has near stock pressure relief preload settings, but has longer gears setting in a deeper cavity that is able to pump more liquid at that set pressure. A high volume pump will pump enough oil to keep worn or loose bearings supplied with more oil than they loose out the sides thus maintaining pressure. This is important as without adequate pressure, insufficent oil will be pushed above the crank to things like lifter bores and push rods and rocker arms.

Oil retuns to the pan via gravity and passages cast or drilled for return. From rocker arms which are highest, it flows to the ends of the heads and falls through "gulleys" usually into lifter valley and down past cam and crank to fall into the pan. Any excess that is let go by loose bearings just falls. Much of it get's splashed to block sides and runs down to the pan.

Some vehicles have the pressure relief in the filter adapter or block. It serves same purpose, it just isn't in the oil pump itself. Once on a '65 Pontiac GTO we had gone through several engines and so we decided to just block that relief. Started it up, blew a filter wide open and ruined the gage. Replaced filter with a Fram and the 80 psi gage with a 200 psi gage, saw 160-170 psi at start up. Fram held it. We "undone" it after that, seemed like maybe too much?

 

"White smoke" is probably blown head gasket or warped head........