Hi-
I've been having a strange problem with my 86 4bbl 305.
It has about 175,000 miles on it.

Recently, upon starting oil pressure is about halfway to full, which i think is about... 40psi maybe. Then slowly after that, it drops down to zero. After plummeting to zero, it goes up when i mash the gas pedal. The idiot light never comes on.

So to the questions:

1) I was thinking maybe the oil pressure sending unit is bad. If this is true, I'm wondering where its at so that I can either hook up a mechanical guage, or replace the old one.

2) Since it's about time for an oil change, I was thinking about what kind of oil to buy and came to the realization I may have bought the wrong kind of oil last time. I think I bought 10W40, since its a high mileage engine and its supposed to have 5W30. Was this the correct assumption?

Thank you very much in advance!

 

i recently had the same problem on my 92 rs, hook up a mechanical gauge to the oil gallery tap on the back of the motor next to the distributor, you might even have a tap next to the top of the timing cover, mine didn't, but some blocks are without the tap near the timing cover, if you have it, it would be much easier to hook up a gauge...check your pressure and replace your sending unit if it reads incorrectly