Mechanical Oil Pressure Gauge conversion

[scott2093]

Bad news is, i still have low oil pressure. It reads exactly what my factory guage reads.

How low is it?
I'm afraid mine doesn't look too good either but 16psi at idle in gear is acceptable from what I understand...

 

[scott2093]

Did the vehicle the engine came out of have the same pressure range on the gauge as the vehicle it's going into (0--60 vs. 0--80, typically.) If so, and it has the same number of electrical terminals, it's interchangeable.

Grabbed this from another thread...
I swapped my dash cluster last year ...The new oil pressure gauge goes to 80. My old one went to 60. Is this why my oil pressure has always been reading high? I didn't know until I put this mechanical gauge in.....

Also, I did a BG EPR crankcase treatment before changing the oil today. I believe SAATR mentioned doing a treatment and running some oil and filter 1500 miles, doing another treatment, running some oil and filter another 1500 miles, then changing the oil and filter once more was a good treatment for noisy lifters. Mine are actually quiet apart from a tap every now and then but I wanted to clean things up a bit since I know it was looking dirty when I had my intake off cleaning the lifters.

Anyway, my oil pressure dropped from 16psi at hot idle in gear to now 10psi...I guess that's what the first big mark on the AutoGage meter is... get 30 psi at 1500 rpm driving 55 mph ish...
18-20 psi hot idle in park.....
rpms kinda low in gear 500...maybe lower when in gear idling.....

I used STP full syn high mileage and STP filter...cheapest syn at Autozone
Was running Mobil One oil and filter previously....

 

[Schurkey]

Sudden, harsh oil detergent treatments are as likely to move sludge INTO the lifters as to clean them out. They may--or may not--do a fine job on varnish.

Hydraulic lifters have a fairly large oil inlet. The oil outlet is microscopic--the tiny clearance between the ID of the lifter body, and the OD of the lifter plunger. Sludge and contamination can get in easily, and is then trapped inside 'cause it can't get out.

In the meantime, all that semidissolved sludge is circulating through the bearings, and along the cam lobes and pistons.

 

[Road Trip]

Anyway, my oil pressure dropped from 16psi at hot idle in gear to now 10psi...I guess that's what the first big mark on the AutoGage meter is... get 30 psi at 1500 rpm driving 55 mph ish...
18-20 psi hot idle in park.....
rpms kinda low in gear 500...maybe lower when in gear idling.....

I used STP full syn high mileage and STP filter...cheapest syn at Autozone
Was running Mobil One oil and filter previously....

10 psi at only 500 rpm is not a failing grade. Especially if you are seeing 30 psi
at 1500 rpm/55 mph. Also 18-20 psi hot idle in park is solid.

Q: What is the viscosity of your fresh oil? If it's a 5W-30, and you like the way
that the STP oil works in your engine, then I propose that you try their
15W-40 'Diesel' oil that also happens to have earned a 'SN' rating.
(When reading engine oil ratings, S = Spark Ignition {gas} while
C = Compression Ignition {diesel}.)

Note: Not all Diesel 15W-40 oils are also rated for gas engine use. (See attached.)
The nice thing is that this is oil is currently on sale for $19.99 for a 1 gallon jug at Autozone.

In addition you have clear, unambiguous oil pressure readings from a
mechanical oil pressure gauge with a good track record. (at least for me.)

So if you are currently running a 5W-30 and you try the 15W-40 on the
next change I wouldn't be surprised to see higher oil pressure than you
are currently seeing. On higher mileage engines with larger clearances
it used to be a common practice to run a higher viscosity oil in order
to improve the oil pressure/maintain that incompressible oil film between
the moving parts.

Would be neat to see the same oil gauge with the engine in the same
warmed up state with what the 15W-40 will give you. Or are you already
running the higher viscosity engine oil?

 

[scott2093]

I have been running 5w30 synthetic since all my problems started..lol And still am... I should say since my lifter journey started actually...
Used to just do 10w30 conventional forever and ever...
Engine sure was dirty when I opened the covers...
I'll try the heavier stuff next for sure...looks nice..... Hopefully everything stays right where it's at til then..

 

[Road Trip]

I have been running 5w30 synthetic since all my problems started..lol And still am... I should say since my lifter journey started actually...
Used to just do 10w30 conventional forever and ever...
Engine sure was dirty when I opened the covers...
I'll try the heavier stuff next for sure...looks nice..... Hopefully everything stays right where it's at til then..

Here's a page right out of the '99 FSM that graphs which oils are recommended for any given temperature range:

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The default for a new SBC with new clearances throughout is a 5W-30 oil. And if you were to replace your existing
crate motor with a new one then whatever the (re)manufacturer specifies in order to maintain the warranty then that's
exactly what you run. Period.

But notice that even when the GMT400s were new the General was fine with all the oils listed above as long as you
honored the ambient temp limits. (Looks like 15W-40 will actually easily work year-round in FL. (!)

And back in the late '90s the 'SJ' oil rating was the latest & greatest. Now we're up to the 'SN' rating. So the oil
viscosities that we have been discussing actually does not deviate from what the GM engineers originally approved
for your SBC. Except that today's oil is supposed to be a couple of incremental steps above & beyond the 'SJ' oil
originally spec'd in the FSM.

So there's no shenanigans being proposed for your engine. It will interesting to see if the thicker oil will translate
to a quieter engine while at full operating temperature in the real world.

Keep us in the loop --

 

[scott2093]

So there's no shenanigans being proposed for your engine. It will interesting to see if the thicker oil will translate
to a quieter engine while at full operating temperature in the real world.

Jeez... I should just spring the extra cash to go ahead and do it now for the benefit of my motor? Not like I'd have to replace the filter.
Thank you

 

[Road Trip]

If it was me, I would go ahead. The filter is so fresh that it isn't going to
make that much of a difference to leave it in place. And changing the oil
right when you return from the store while the existing engine oil is
still warm will ensure the best possible drain.

And the clean switch from the 5W-30 to the 15W-40 (and even staying with
the same brand) should tell the tale in a quantified way thanks to the
mechanical oil pressure gauge. I hope you get to do this.

 

[scott2093]

If it was me, I would go ahead. The filter is so fresh that it isn't going to
make that much of a difference to leave it in place. And changing the oil
right when you return from the store while the existing engine oil is
still warm will ensure the best possible drain.

And the clean switch from the 5W-30 to the 15W-40 (and even staying with
the same brand) should tell the tale in a quantified way thanks to the
mechanical oil pressure gauge. I hope you get to do this.

Thanks. No issues with going from synthetic which I'm seeing the diesel isn't. From what little I've read in the past, it doesn't matter?
I swear I always heard it was a big deal to go back to conventional when the synthetics first started catching my radar....That was a long time ago....

 

[Road Trip]

Thanks. No issues with going from synthetic which I'm seeing the diesel isn't. From what little I've read in the past, it doesn't matter?
I swear I always heard it was a big deal to go back to conventional when the synthetics first started catching my radar....That was a long time ago....

No worries about moving from the synthetic back to conventional. Don't quote me, but a conventional modern 'SN'
rated oil would outperform some of the older synthetic oils from way back when that FSM was being printed. On paper. :0)

About the only other thing I can think of where the heavier conventional oil might be different
is surrounding oil consumption. As in, depending upon the clearances inside your motor, it
might make for *lower* oil consumption than the thinner synthetic that's currently in there.

The bottom line is that I don't think that you are going to break any rules with the proposed change.
Not even close to pushing the safe envelope on this old school SBC. (with bonus roller lifters)