Oil pressure issue 1967 430

Hi, When warm,the oil pressure gauge bounces erratically when RPM is around 500. It goes back to normal when I throttle up to 600+ 1967 Riviera 430 What's going on here? Sorry I couldn't post the video here

https://www.facebook.com/reel/737388584827665?fs=e&s=TIeQ9V&mibextid=4yZLJr

 

I can't see the video but at that low of an RPM, I can imagine it is bouncing. The oil pump is turning at half engine speed it may not be enough to keep the oil pressure stable. I wouldn't idle it down to 500 in any case. Most call for 650 in gear kind of numbers.

 

Crank it up. Should be about 650 in drive with foot on the brake when fully warmed up.
750-850 RPM at idle in Neutral/Park.

Engine's idling too low will have a "fast/slow tempo" and if you had a super responsive tach, you would see the needle bouncing like/with the oil pressure gauge.

 

I have a question re oil pressure.
What is the normal oil pressure for a 1970 Buick GS 455 rebuilt 3,500 miles ago.
Mostly stock, mild Comp Cam (little more than a Stage 1 cam), port matched, Stage 1 cast heads, aftermarket 10.5 compression pistons (Kenne Bell maybe 2015-2016 model year).

What is the normal oil pressure @ 700 rpm idle?
@ 2000 RPM?
@ 3000 RPM?

Reason why I'm asking - With A/C on, my idle went down to 500 rpms and below, engine stalled out.
I have since installed a carburetor idle solenoid to prevent A/C stalling out engine.

When the car was stalling, 500 to 450 rpms and my oil pressure read 9 pounds of oil pressure.
This concerns me, not that this will be an ongoing issue (engine stalling), but it has me wondering what oil pressure is correct for this car.
I have no clue what normal oil pressure reading are supposed to be.

I have a new TA oil pump. I also have a digital oil pressure gage that reads oil pressure in pounds.
Is the 9 pounds of oil pressure caused by the engine going into a stall mode? Should I be worried?
Appreciate any answers/help. Vet (Navy)

 

With an automatic, you need minimum 650RPM in Park/Neutral. You need 750RPM (minimum) in Drive, foot on the brake.
Better is 850 RPM.

Some cars with Air Conditioning dashpot helping to "up" the RPM when A/C kicks in, is sufficient, but increases idle does not hurt anything.

Some people get fixated on the lowest RPM that the car will operate on, but, a car with faster idle is not hurting anything. (except economy of fuel)

Certainly, having a car operate more for performance, may cost a bit on fuel economy, but if the car stalls, is "finicky", or sounds "awesome," with a lope but is temperamental, maybe a few more RPM is worth the issues you don't have to deal with...


Low end oil pressure when fully warmed up is good as long as you have "any", and that you see instant increase when you come off idle, and at least 10 lbs per 1000 RPM.

That's the "best all around answer".

My 430 runs near 80 on cold start.
Drops to 55-65 when hot on cruise, drops to 5-10 at idle, but jumps when you barely touch the throttle. (10w-30). (Manual transmission)

 

Thanks Mike. Looks like my car is running about the same oil pressure that your car does.
Looks like mine is pretty much identical to your specs ---Drops to 55-65 when hot on cruise, drops to 5-10 at idle, but jumps when you barely touch the throttle. Mine is a TH400 trans.

I just needed a standard to go by. Again, thanks Vet (Navy)

 

These cars had lights, not pressure gauges. The oil pressure senders were anywhere from 3-9 PSI as the "allowance" when (mass) produced.

Back in the old days, when someone complained about the light coming on, replacing the sender unit often "fixed" the problem.

Some folks noticed a light start flickering, when it was about time to change the oil.
Some folks saw a light after a few hours on the highway and pulling off to get gas.
Some folks never saw a light under any conditions.

The point, is, when you put gauges in the car, you see things you never knew about before.

As long as you have any oil pressure on a guage moving at idle, it comes up on increased RPM, and you have the "10 PSI per 1000 RPM" you are usually fine.

Folks racing or otherwise pushing things, will understand all they need, for what they require of their cars.

Don't fall into the trap of chasing everything you read or are told, because such things will keep you up all night, worrying about nothing.

Enjoy your car, but if you have a concern, ask.

Better to ask and be a bit OCD, than to break something.

 

Great Advice. Thanks Mike, Vet....

 

All good advice.

Regarding the "bouncing" of your gauge in the video, I think it's more of an electrical issue, not an engine issue. The oil pressure sender's output is electric, it's just a variable resistor inside that changes voltage resistance depending on actual oil pressure. Downstream from there is 56 year-old wiring, good or not-so-good ground wires engine to chassis/body and finally the dash gauge itself.

Getting accurate and dependable dash gauge readings means chasing all electrical stuff above.

Checking oil pressure with a mechanical gauge should be a good first step for engine diagnosis. Next is more difficult on the electrical side to get the dash gauge behaving correctly!

Devon

 

Granted. I think Autometer's lack of damping is is on another level compared to a stock sender/wiring/dash gauge. The OEM system shouldn't be dancing like that. 1967 customers wouldn't be happy...something else is up to figure out.

Devon

 

Thank you so much Larry.
As always you are a huge help to everyone on this forum.

I'am new to this forum, so it's especially helpful to me and I'm so appreciative for your help.

I would love to see your archives of Buick information.
You must be super good at getting to your info, seems like you reply super quick. Vet (Navy)

 

Thanks for the tip. So that where some of the Buick info is located.
The forum categories are so large, would have taken me years to find it. Again, thanks. Vet

 

If the gauge is electrical, you can add damping electrically in the way of an electrolytic capacitor

 

Sending unit

 

Yeah,

That gauge, sending unit or wiring/ground problems.
Abnormally pretty erratic.

Tom T.