Low Oil Pressure 350 Chevy

DAVIDLOFLAND · Post by **DAVIDLOFLAND** » Sun May 06, 2012 2:10 pm

F-32 with 350 Chevy's - Rebuilt longblocks 6 years ago, and now have 1200 hours on rebuilds.

Stbd has great oil pressure all the time.

Port is doing the following...

Cold - 50-60 psi.

Warm - 3200 rpm planing cruise - 25-35 psi

Warm - 1100 rpm hull speed cruise 10-20 psi

Warm - Idle after planing cruise, near zero psi.

Question is, could a failing oil pump cause these symptoms?

Easier to change the oil pump than to rebuild the engine, but even changing the oil pump is fairly major, because you have lift the engine. No sense in changing the oil pump, without any chance of correcting the problem.

Any ideas you guys have would be greatly appreciated.

Thanks,

Dave

gettaway · Post by **gettaway** » Sun May 06, 2012 2:32 pm

stupid question,

have you checked the oil pressure sending unit and gauge?

DAVIDLOFLAND · Post by **DAVIDLOFLAND** » Sun May 06, 2012 2:45 pm

Seperate sending units for guage and buzzer. They both confirm the low oil pressure.

EM63 · Post by **EM63** » Sun May 06, 2012 4:41 pm

Hi David - what about the temperature of the port side engine in slow speed ?
--
Greetings - Heiner

DAVIDLOFLAND · Post by **DAVIDLOFLAND** » Sun May 06, 2012 4:46 pm

Normal. No overheat.

EM63 · Post by **EM63** » Sun May 06, 2012 4:56 pm

Does the upper helm and this engine are really 'grounded' - means heavy Minus-poled (I do not have the riight words for).
--
Greetings - Heiner

DAVIDLOFLAND · Post by **DAVIDLOFLAND** » Sun May 06, 2012 5:32 pm

Hey Heiner,

Not sure exactly what you're asking, but yes, both helms and engines are grounded (-).

It is an absolutely confirmed low oil pressure issue. It was not a sudden onset, as I watched the pressure get lower last season. I added some Lucas Oil, which helped a little bit (for a while), but the problem continues to get worse.

Question is, do oil pumps fail? If so, can they gradually get weaker, and cause the symptoms described in the first pane of this topic?

EM63 · Post by **EM63** » Sun May 06, 2012 5:43 pm

May be - you can ask your next Chevvi-dealer about that.
Sometimes it is just a verry little problem with any car-made spare part.
I hope so.
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Greetings - Heiner

DAVIDLOFLAND · Post by **DAVIDLOFLAND** » Sun May 06, 2012 6:03 pm

Googled "Can a failing oil pump cause low oil pressure on a 350 Chevy"?

And, of course, found completely contradictory testimonials.

One said, "If you have good pressure when the oil is cold, then the pump is good".

Another said, "I changed the oil pump, and pressure is now normal in all states of temperature and RPM".

WT*

alexander38 · Post by **alexander38** » Sun May 06, 2012 6:24 pm

Dave, A weak pump will pump cold oil real good, then drop RPM after it warms up, but have you checked the oil for bearing metal ?

rooferdave · Post by **rooferdave** » Sun May 06, 2012 6:28 pm

I am interested in this as my porshe 944 is doing the same thing,

1st thing to do imo is change the oil and add a product such as slick 50 to minimalise damage due to the low pressure. Sludge in the oil pan or a bad oil filter could cause low oil pressure at idle due to resticted path, my point is adding one of those oil treatments to clean the engine and changing the oil and adding the slick 50 is not expensive and can do no harm, I would do the above and if it does not work as I said the slick 50 is sopposed to be able to have an engine run with no oil (so they claim) and will buy you time to find the problem. I have an ex formula one mechanic on staff and will check with him tomorrow for you. As to why I did not have him look at my porshe yet he is too busy fixing things that EARN money not waste it

prowlersfish · Post by **prowlersfish** » Sun May 06, 2012 6:58 pm

It could be the oil pump or worn bearings ( assuming the oil is not thinned out and filter clean ) . Thats really is the only 2 things that will cause low oil pressure .

Stripermann2 · Post by **Stripermann2** » Sun May 06, 2012 8:19 pm

Couple of more... Restricted pick-up screen, cracked pick-up tube sucking air.

captainmaniac · Post by **captainmaniac** » Sun May 06, 2012 9:03 pm

I am not really overly mechanically inclined, so I just look at symptoms to try to find patterns. Given that...

You say you have confirmed the problem is real - how? Are you dual station and pressure drop shows on both upper an lower gauges? Or have you used a manual pressure gauge? I am not trying to be a pita here... just to understand how you actually confirmed the problem.

Don't think you said what oil you are running (brand, viscosity), or what you are using for filters, or when the oil or filters were last changed, or how many hours since last oil/filer change.

I have seen people suffering from similar symptoms because of pickup tubes falling off, too much time between changes causing crud to block pickup tubes, too low a viscosity (though would have trouble seeing that on in Alaska!), too many additives, or overfilling causing foaming, without it being a problem with the oil pump itself.

Any other behaviour stuff - like is engine exhaust showing more smoke than normal, or more steam than usual? Sounds that weren't there before? The more info the real experts on this forum have, the better they are likely to be able to diagnose your underlying problem.

The Dog House · Post by **The Dog House** » Mon May 07, 2012 7:26 am

captainmaniac wrote: Any other behaviour stuff - like is engine exhaust showing more smoke than normal, or more steam than usual? Sounds that weren't there before? The more info the real experts on this forum have, the better they are likely to be able to diagnose your underlying problem.

How much steam out of the engine exhaust is normal? Last weekend was very humid, and there appeared to be more steam coming out than the weekend before. Would the high humidity make the steam more visible?