Thread: Newb Oil Pressure question

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I have a 32 coupe with a SBC 327 that was put together in 1995. Last couple of seasons it seems our oil pressure is going south. At start-up it is around 35-40 but after heat up at idle it is close to 0 maybe 4 to 6 running down the road it sits at about 20. Engine runs fine and has no valve clatter. We take car on a couple trips a year and has about 22,000 miles. I am concerned about Louisville this year with this pressure. Does this engine need to come out and be redone or what suggestions are out there. Is this common? I have run 20/50 castrol and just tried 15/50 mobil 1 same results.

Mechanical or electric oil pressure gauge??? Might want to check it with a mechanical gauge that is known to be accurate before making a decision.... With that few miles on the rebuild, it should certainly not be failing yet if it was a good build.... Can you get the pan off without pulling the engine? Always a possibility that the pickup is plugged, or maybe the car bottomed out on the pan and pushed the pan tight on the oil pickup??????

Assuming Dave's suggestions don't pan out (pun intended), try these suggestions....
First thing I would do is change to a premium filter such as Wix and see what happens. If pressure is still low, drop the pan and turn the motor over by hand at the crank to service all the rods with new bearings. Loosen the main caps to let the crank drop down just a smidgeon and change the main bearings and rear seal, then re-torque the caps. Install a new standard (not high pressure, not high volume) Melling oil pump. Bolt up the pan and fill with 10W-30. Anyway, that's what I would do before I pulled the motor for an overhaul. This assumes you have good cylinder pressure and mimimal blowby.

I had a boat that did exactly that...........oil pressure started to drop into the 6 pound mark at idle as time went on. Changed the sender and oil pressure went back up to 20 or pounds at idle. The suggestion to try a mechanical gauge first is a good one, even gauges can go bad.

You might also drop the pan and put in a new pump as Richard suggested. The relief spring can weaken with age or the pump can start going bad. We used to stretch the relief spring out in the old days to get higher oil pressure.

Don

if the distributor is pushing down .the pump gear can dig in the pump end plate run metal thru pump and wear out the oil pump

It is an electric gauge but I checked it with a mechanical and also changed the sending unit same pressure. The pan has not been hit but pump could be clogged. I think pan is accesible from under car. Is changing the bearings doable for a rookie. I have done alot of stuff over the years (heads ect.) but have never changed any bearings. I guess I could maybe give it a go, any tips for process and how do I get the right size bearings?

Originally Posted by techinspector1

... Install a new standard (not high pressure, not high volume) Melling oil pump. Bolt up the pan and fill with 10W-30.

Tech - Why not high pressure, high volume? (Not that he needs it with a mild mannered engine, just curious.) Also, why 10W-30? Why not 20W-50? I'm not trying to confuse the issue; my engine experience is limited and I'm curious about your reasoning.

Start with the oil pump. I say that because you say you are a little new to this, and while changing bearings isn't the hardest thing in the world it does require a little knowledge. As for how to know what bearings you would need if you do go that route, each bearing will be marked on the backside, and say something like "std" or ".010" etc. That will tell you if you have standard sized journals or if they have been turned.

The condition of the old bearings will tell you a lot too, but once again, you might want to enlist the help of someone who has been down this road before to give you a hand.

Don

My '68 SBC 350's oil pressure is about the same. I normally run 10w30 in the early season and then switch to heavier grade in summer. Mine is about 40 on start and warm up, 6 - 10 warm idle. Climbs when the tach climbs. Not uncommon in sbc's.

Originally Posted by J. Robinson

Tech - Why not high pressure, high volume? (Not that he needs it with a mild mannered engine, just curious.) Also, why 10W-30? Why not 20W-50? I'm not trying to confuse the issue; my engine experience is limited and I'm curious about your reasoning.

I would like to read Techs answer also,but I'll bet it's because the high volume/high pressure pumps rob horsepower and wear dist.drive gears, all you are doing is pumping extra oil to the top end. All ya need is 10 psi for every 1000 rpm,"just a rule of thumb" and the stock oil pump is more than capable of that.

Originally Posted by J. Robinson

Tech - Why not high pressure, high volume? (Not that he needs it with a mild mannered engine, just curious.) Also, why 10W-30? Why not 20W-50? I'm not trying to confuse the issue; my engine experience is limited and I'm curious about your reasoning.

A street driven motor with a stock 5-qt. oil pan doesn't need high pressure or high volume. All that does is put additional strain on the distributor drive gear, cam drive gear, drive shaft, pump and ultimately the timing set at the front of the motor. Now, if a guy is gonna buzz the motor, then he's going to want to design the system with a bigger pan and more pump. Here's usmcdad's original statement....

"Last couple of seasons it seems our oil pressure is going south."

That tells me that BEFORE the last couple of seasons, all was well with the oil pressure. And that tells me that either he has changed the brand of filter he's been using and the filters are contributing to the low pressure (have read lots of bad juju about Fram in the past year) or the bearings are going away and bleeding pressure off or the pump has clearanced itself loose between the gears and the pump body or the relief spring has gone weak or the spring piston is sticking in its bore.

If all the mechanicals are correct in the motor, it doesn't need anything heavier than 10W-30. My old 300-6 Ford motor required 2 cans of STP and 40weight oil to get enough oil pressure to operate at all before I rebuilt it with bearings and standard pump. Now, I use 10W-30 with no additives except ZDDP and the pressure is 45-50.

My 350 is the same, 6-10 lbs on idle but raises as soon as you touch the go pedal.
I was concerned at first but have been running it 7 years now like that and even a few passes at the track and haven't had any problems.

Ken

Thanks for all your help guys I am sure glad I found this site, there is a unlimited reading and info hear. Just an update I got and installed a new oil pump today and on startup it jumped right to 60lbs. I haven't seem it up there for a long time. So I am guessing something has changed, I did not take it out and heat it up because it was a wet day here today. I sure hope this was the answer and will post an update as soon as I can take it out. Thanks again.

take the old pump apart and look at the end plate if all tore up .you may want to shim up the dist or move the slip collar you can just add another gasket on the dist or buy a shim kit moroso sell s them still i think

Tech - Thanks for the explanation. I've had people tell me not to use high volume pumps for street engines in the past, but nobody could ever explain why. I always got an answer like "It's bad for the motor." Huh? Anyway, I never considered the drag on the distributor gear and timing set... I know where all the pieces go and how to use a torque wrench, so I assemble my own engines, but I'm not really an "engine man" and my engines are always pretty mild-mannered. I rely on the guys at the machine shop, what I read, and what little I've learned over the years.