SBC oil pressure problem

Got a 350 Malibu 1980. Motor was rebuilt with all new parts that fell within specifications. Oil clearances were where they were supposed to be (plastigauge). Motor runs very strong, but oil pressure drops to around 25 psi at idle when fully warmed up. Initial start pressure is right at around 60 psi. Along with the pressure drop I am getting valve train noise from BOTH banks and it is really pissing me off! Sounds like an oil pressure problem to me. Running a Fram filter and Castrol gtx 10-30. Looking for advice. Thank you in advance.

John from NC

I won't say that you don't have an oiling problem, but your oil pressure is not likely the issue; that is typical Chevy, all the way. Most Chevy's oil pressures run that way, and it is just fine; as the engine speed increases, loading on bearings and friction surfaces increases, and you need more oil pressure, but at idle, everything is relaxed, so to speak, and the pump slows down and pressure drops off. As long as it acts that way, and does not drop below about fifteen psi at idle (an arguable point for some), or go over about sixty psi (again, arguable for some folks) at speed, for a daily driver, you're good. As to your valve train noise, that bears some investigation; maybe a cam bearing installed wrong so oil is not getting to the lifters and pushrods and upper end :CRY:, or just some "assembly junk" plugging up a pushrod :(. There are a lot of little details that could be causing it, even just needing re-adjusting after break-in.

I've got a 95 Z28 that run just like yours does. I rebuilt it last year and she's built right with a new Melling high volume oil pump and all new bearings throughout. When cold, it runs 65psi and after warmed it will idle at around 25 psi, and back up to 60 psi anything above idle . LT1 I have always has valve train noise. I As far as you 1980 Chevy making noise, it may or may not be a problem. Try and rule out all you can before more drastic measures are taken. Like Rrumbler said, it could just need the rockers readjusted.

you will get some valve train noise with roller rockers. when oil is cold it will be thick= hi psi when the oil warms up it thins .i seen engines set for kill loose on mains and rods.i seen them that have less then 20 at idle hot and as long as oil psi builds as rpms go up your fine . if rocker are steel stamp stock shoe type they get stem marks worn in and will make noise they go in and out of lash .alot of the builds with hyd lifter engines i drill 030 or so hole in the front lifter galley plugs to help with air lock gm did this on the early bbc .all the newer gm sbc have the plugs drill from GM.on the bearings i have seen them verry alot from the markers so you realy have to watch them for size getting past .002.5 on the rods/mains is a big deal with a stock pump if your looking for big numbers on oil psi i posted some of this on your other post

I had the same problem with a sbc I had rebuilt and like the guys stated above its pretty normal. You can raise the pressure some by changing out the spring in the oil pump and going to ao thicker oil. 60PSI cold sounds like to much and 25PSI hot seems about right. Whats your valvetrain set up? Is it all stock?

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Originally Posted by tiorunder

Got a 350 Malibu 1980. Motor was rebuilt with all new parts that fell within specifications. Oil clearances were where they were supposed to be (plastigauge). Motor runs very strong, but oil pressure drops to around 25 psi at idle when fully warmed up. Initial start pressure is right at around 60 psi. Along with the pressure drop I am getting valve train noise from BOTH banks and it is really pissing me off! Sounds like an oil pressure problem to me. Running a Fram filter and Castrol gtx 10-30. Looking for advice. Thank you in advance.

John from NC

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Hi John,
I gave up using castrol and switched over to Valvoline about 14 years ago
on my 3 V8's and a straight 6 and have never had a bearing/ lifter or any
other kind of problem.If I went elsewhere it would be mobil or Shell.
Synthetic oils from all over the world are on sale out here and go on sale
sale for 4.55 litres @ $48 to over $110 depending on the purpose.
I always stick to 20-50 grade normal oil all year round and the oil
pressure in our many variable conditions are


constant about @ 15lbs hot idle to 45 highway conditions.
One time one mechanic gave my new 355 a tubful of 40/70 which gave
the gauge reading 105 @ 3000 rpm on a stinking hot day and kept the
radiator fans working overtime on the 240 mile trip. On arrival another
tubful of 20-50 and a same name filter were put in place.Back to basics.
Compared to what we spend to build these motors that we rely on the
costs of oils and filters is not bad and a necessary insurance so why not
get it right ASAP?..Good luck with the project..S/King.....




filter was immediately set in motion..Back to normal....

The problem you have posted has shown up on other sites also,the culprit seems to be the Fram filters, change to an AC Delco or Wix and see what that does.Google "Fram Filter problems" and watch what comes up,quality has gone down hill!

Quote:

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Originally Posted by tiorunder

Got a 350 Malibu 1980. Motor was rebuilt with all new parts that fell within specifications. Oil clearances were where they were supposed to be (plastigauge). Motor runs very strong, but oil pressure drops to around 25 psi at idle when fully warmed up. Initial start pressure is right at around 60 psi. Along with the pressure drop I am getting valve train noise from BOTH banks and it is really pissing me off! Sounds like an oil pressure problem to me. Running a Fram filter and Castrol gtx 10-30. Looking for advice. Thank you in advance.

John from NC

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Hi,
Your oil pressures are O.K. Does the motor knock in the first few
seconds after starting then cuts out? Has your engine block have a
removable blind plug alongside of the water pump area left hand side
facing the engine that generally would have a square head on it?
If so you can remove the plug and start the motor for a few seconds
and see what oil volume comes out.It should be a great powerful squirt.
With my Motor Oil--
I forgot to mention that the Valvoline was 20/50 was high detergent.
When Valvoline filters became scarce I tried a few others and then
changed to K&N which have done the job well. I change the oil about
5000 miles and It could go a lot further but I like to keep everything
nice and clean and lower the maintenance costs.You say the motor
runs strong- How strong and how often?? I Would like to see this
problem solved before it solves itself the hard way..Good Luck S/King.
P.S. I rarely push my ZZ4 past 4000RPM as there are no wide open
spaces in my local area...

By any remote chance.... Did you put the screw in oil restrictors in the lifter supply rails in the rear of the block?

Also, just my .02, dump the Fram. Go AC or Wix or Donaldson.