352/360 oil pressure problem

[roadshowbob]

Hello All,
I am new to the FE motor but got am trying to learn since I scored a nice 65 with a 352. The issue I am having is this. The 352 that was in the truck when I bought it had a lot of blow by out the PCV and oil breather caps. When engine was warm, oil pressure would drop to zero on gauge and oil light comes on. This motor also had a bottom end knock so I bought a used 360 to replace the 352 until I can rebuild it. The 360 ran very well with oil pressure on gauge reading between 15 and 30 psi under all conditions. I put a few hundred miles on it and all of a sudden it has the same oil pressure drop when you come to a stop sign, engine warm at idle in gear. Once you bring the rpms back up or put trans in nuetral, the pressure will slowly climb back up. The oil in the truck is quaker state 10-40 and freshly changed. The 360 had sat for a long time before I installed it. Can anyone give me some idea of where to start trouble shooting this problem or a solid fix for it?

Thanks

 

[blacksnapon]

Hello All,
I am new to the FE motor but got am trying to learn since I scored a nice 65 with a 352. The issue I am having is this. The 352 that was in the truck when I bought it had a lot of blow by out the PCV and oil breather caps. When engine was warm, oil pressure would drop to zero on gauge and oil light comes on. This motor also had a bottom end knock so I bought a used 360 to replace the 352 until I can rebuild it. The 360 ran very well with oil pressure on gauge reading between 15 and 30 psi under all conditions. I put a few hundred miles on it and all of a sudden it has the same oil pressure drop when you come to a stop sign, engine warm at idle in gear. Once you bring the rpms back up or put trans in nuetral, the pressure will slowly climb back up. The oil in the truck is quaker state 10-40 and freshly changed. The 360 had sat for a long time before I installed it. Can anyone give me some idea of where to start trouble shooting this problem or a solid fix for it?

Thanks

under those circumstances, I'd go worn bottom end and oil pump. You could probably delay it for a while just putting in an oil pump, but you're in for a rebuild, in my opinion.

 

[LEB Ben]

I agree, the engines you're talking about are at least 33 years old...so a complete rebuild is in order. However, are you getting your psi readings from a mechanical guage or from the dummy in dash guage? If it's the dummy guage, try throwing in a new sending unit...if that doesn't give acceptable psi readings, then it's time for a rebuild.

 

[1985 Ford F-150]

You could also just drop the pan and put a high volume oil pump in it for a temporary fix. Theyre only 40 bucks and then ya need a pan gasket and them are a couple bucks.

 

[roadshowbob]

the reading is from the factory gauge on the right outer portion of the dash. I had already figured on it needing an oil pump. It's just a temp replacement until I can get the original 352 rebuilt. Thanks for the information

 

[1985 Ford F-150]

Try the sending unit first just to see if itll help.

 

[roadshowbob]

will do that, plan on a new oil pump this weekend if possible.

 

[1985 Ford F-150]

Yeah if the sending unit dont work then either hook up a real gauge to it or go ahead and put in the high volume oil pump.

 

[roadshowbob]

will do. looks like gauge is reading correct though

 

[1985 Ford F-150]

Well ya never know with them in dash gauges. I like the real one so I know exactly what my pressure is not just if its too low or too high.

 

[LEB Ben]

will do. looks like gauge is reading correct though

Those guages are old and fail over time, there's a reason they're called dummy guages...more than likely the SU is worn out too. So as I said in my first post...replace the SU first...it's the cheapest and the easiest way to see if you really have an oil problem. Next would be to hook up a mechanical guage as Dan suggested. Then as a bandaid fix, a new HV oil pump and some thicker oil. Then it's time for a rebuild.

 

[roadshowbob]

i hooked up a mechanical aftermarket gauge today and the oil pressure will build to around 20-25 psi, then drop at idle to 0. It will build back up once you take the rpm's up a bit over idle and it will hold as long as you don't allow it to drop back to idle. Looks like a new hv oil pump bandaid is coming this weekend.

 

[1985 Ford F-150]

Yeah sounds like its time. What rpm are ya goin to?

 

[roadshowbob]

It is a used engine so I knew it wasn't a permanent fixture under my hood, Just a bit peeved since I just got it running very well and it craps on me. As far as what rpms, I have the stock 3.25 rear axle and the cruise-o-matic so my rpms are pretty low and it does mostly low speed trips but not really too bad on the stop and gos.

 

[1985 Ford F-150]

Try gettin up to about 2500 rpm and then see what the gauge says. Also what viscosity oil are ya usin?

 

[LEB Ben]

This just doesn't make a whole lot of sense to me...it goes from running great and then out of the blue it doesn't hold any oil pressure. Is it smoking or using any oil? If not, it may just be that the oil pump is bad.

 

[1985 Ford F-150]

Never mind I re read the original post and if I were you id check the level of the oil and change it to 15w 40 rotella or delo. Quaker state is junk oil. It might burn some and ya cant see it smokin if its faint.

 

[roadshowbob]

changed oil to 10-40 pennzoil and it had no change. At 2500 rpm the oil pressure will build and hold, just once you stop at a stop light/sign and let it idle in gear the pressure drops again

 

[1985 Ford F-150]

Try thicker oil like 15w40 or SAE 30w if that dont bump it up then go head and do the hv pump.

 

[roadshowbob]

put in a new melling hv pump today and solved my oil pressure issue but now have the rods hammering a tiny bit so it's time to get the 352 torn down and ready to rebuild. thanks for eveyone's input