Oil pressure question

[mtully79]

Oil pressure at near peak when I first start it up, then falls slowly over the course of 15-20 mins. It's only started doing it the last 2 or 3 trips after having on the road for the past 3 months. I only take her out on weekends around town, so she's not a daily driver. Any ideas?

[jaros44sr]

Originally Posted by mtully79

Oil pressure at near peak when I first start it up, then falls slowly over the course of 15-20 mins. It's only started doing it the last 2 or 3 trips after having on the road for the past 3 months. I only take her out on weekends around town, so she's not a daily driver. Any ideas?

May be just the viscousity of your elixior, since it is hot out now, maybe the ambiant temp. and engine temp. are affecting it....what weight oil are you using?

[vegadesign]

sounds like the oil is heating up to quick
may need heavier oil depending on what your weather is like
what engine and setup do you have?

low viscocity oil will start to do that when its running for while because the heat thins it oil making it harder for the oil pump to pick it up

[mtully79]

I'm running 10w-40 synthetic oil. I've got a 350 in there, temps have been higher here at the beach the past month as well. Truck is garage kept out of the sun, oil pressure shoots up as soon as I turn the key.

[vegadesign]

so im assuming its running about 45-60 psi at idle?
after about 15 min or so of driving around at higher rpms it drops down?

[mtully79]

Yea it drops down to normal level after driving for 15 mins. Engine idles at 700 rpm.

[fast eddie1968]

What is your concern to high when cold or to low when hot?

[mtully79]

Originally Posted by fast eddie1968

What is your concern to high when cold or to low when hot?

Concern is the needle is pinned high at startup. It's my first experience with driving the blazer and have no reference as to whether this is normal for the truck or a sign that something is wrong.

[vegadesign]

iv never had one pinned high at start, but if its showing a constant oil pressure later and its not knocking at start up i wouldnt worry about it

[mtully79]

Originally Posted by vegadesign

iv never had one pinned high at start, but if its showing a constant oil pressure later and its not knocking at start up i wouldnt worry about it

Ok, I'll keep an eye on it. Thanks for the response.

[fast eddie1968]

My 72 pick up has factroy oil pressure gauge and it is exactly the same way pegs cold when up to temp it is right in the middle .I think the gauges only read to 60 psi and cold on a good motor with a stck pump its probally 65 psi

[magicoolbus]

The factory oil pressure gauge is indeed a 60 psi unit, unless someone along the way swapped in an 80 psi one (found on larger trucks). The best thing to do if your worried is to get a calibrated oil pressure gauge and hook it up and see what psi's you are actually running. A fresh rebuild with tight oil clearances can easily be 60 to 80 psi.

[mtully79]

Great info, I'll hook it up and see what it reads.

[JDSurge]

Hello everyone. I need some help with my oil pressure port. I have a rear seal leaking and didn't want to take out the transmission right now so I used some Lucas rear seal to fix it. At about the same time, my distributor when out (changed almost every part in it and still didn't fire) so I bought a MSD street fire distributor and it fired right up.
My question is: I now have no oil pressure reading on my new gauge. I removed the oil pressure sending unit at the same time I installed the MSD and there was no oil at the port or in the line. Could the rear seal stop leak have clogged up the oil port at the rear top of the engine, next to the distributor? Or do I have the distributor on wrong or bought a wrong distributor? The gauge was working before all this started but I was reading some threads about the ring around the distributor sending oil to the top end and now I'm wondering if I bought the right distributor.
I have a 350ci out of a 1977 blazer with HEI distributor.
Thanks for any advice to fix this.
JDSURGE
ALso posted a new pic of my blazer with the top off finally. Unfortunately, I went out to a Rod Run party last night and it rained in it for about 20 mins. I hope it will dry out OK.