oil light coming on

Okay, I've got a 1970 Skylark with the 350-2 engine. It has 119,4xx miles and has never been apart. It's been very well cared for. I've owned it for 18 years, the previous owner (a family friend) owned it 18 years, and he bought it from the original owner.

Recently I have had the oil light flicker at a traffic light. Last summer it occurred while the engine idled at the light with the airconditioner on. The oil light went off when I turned off the air. Today I wasn't running the air and the oil light flickered again. I don't drive the car much. Maybe I drive my Skylark 500-1,000 miles a year.

I checked my oil. It wasn't low. The lifters are quiet. There's no knocking. Everything seems normal, but the oil light flickers. Maybe the sending unit is bad. Maybe the oil should be changed.

I have a theory. The engine has never been cracked open. It still has the original timing chain. I have plans on replacing the timing chain. Could my oil light flicker be caused by a crystalized camshaft sprocket that partially clogs the oil pump pickup screen with nylon particles that may have flecked off the old cam sprocket? Again, it's a theory. I'm dealing with a 41-year-old engine pushing a 120k. Maybe I need to bite the bullet and rebuild my engine.

Thanks for reading and thanks for your input.

I think you should assume you have an oil pressure problem until you prove otherwise. An oil pressure problem is usually caused by excessive bearing clearances. You can eliminate a sending unit problem by screwing in a mechanical oil pressure gauge.

You are right, a pressure problem could be caused by a plugged pickup screen. While unlikely, if it were to be cam gear particles, you should be able to notice considerable timing chain slack by rotating the crank back and forth to feel the valve train. 8-10 degrees would be normally worn. I have no idea how much would have to have separated to cause enough screen plugging to cause oil pump starvation, but I wouldn't be surprised at 18-20 or more.

You are probably dealing with a tired motor which is in need of a rebuild.$

Bob is right on with his last statement..... at over 100,000 miles any engine of that era is all used up,,,, it needs a complete rebuild,,, you can buy some time by using thicker oil... but the real problem is worn rod and main bearings and cam bearings and oil pump.....
Believe the oil pressure indicator... it will only trigger when the pressure is below 8 psi....

I really think you simply have a bit of a weak idle that is causing the oil light to come on...

All it would take is an idle a bit too low, a clogged oil filter, some junk partially clogging the oil pickup screen, etc... Any one of these things can cause low oil pressure at idle...

What I would do is do an oil and filter change and if the light still comes on at idle then add an oil pressure gauge... As long as you have about 10 PSI at idle, 30 PSI at 2000 rpms, and 50 PSI at 4000 rpms you are fine... You can get an oil pump rebuild kit from TA performance if you have to, as well as an adjustable oil pressure regulator... I would explore those ideas before I went for a rebuild.

I have seen Buick 350s with over 300,000 miles running strong with no rebuild.

As you stated in your previous post the vehicle has over 100k on it. On Buick small block of that era the oil pressure sending unit is in the front cover in the direct path of the oil as it is coming out of the pump to feed the engine. As a general rule of thumb most time when this happens the culprit is in fact a worn and grooved oil filter housing aadpter. this is due to the oil pump drive gears ride right against this during rotation. Your problem can probably be cured with an oil pump rebuild kit and a new thrust service plate. The kit generally runs around 50.00 for both parts. A word of caution though. If the housing around the pump gears is out of spec the cover will need to be replaced. The repair can be done with the engine in the car and takes less than an hour to complete.

the thrust plate can be acquired by TAPerformance, D&D fabrications. It is made of cast iron, it keeps the oil pump gears from wearing into the oil filter housing, which leads to low oil pressure. If the main bearings on a 2.7 diameter crankshaft, exceed .030 clearance, low oil pressure may result. Low idle can cause this, but it would be around 600rpms.

The thrust plate is easiest upgrade instead of tearing apart the engine. when doing your clearance check, it is possible to have excess clearance. Most will buy a new cover. Taperformance makes some reproductions.

Frugal George's repair: Use a file and minimize the height of the housing at the pump gear cavity. Use a Digital caliper to measure the height before and after. Removing aluminum material will lower your clearance. Finish it off with 230 and 600 wet/dry sandpaper and a perfectly flat block. YOu can use anything with a flat surface as a sanding block: metal ruler, socket, credit card,wooden square, etc.

Anyone, interested in rebuilding there engine, get a $15. digital micrometer and measure and record all your engine components diameters, before you send it out. I went to a reputeable, 20+ year established, and I caught them trying to rip me off with repairs my engine didn't need. The repair was to fix there screw up.

I'd say you could probably raise your idle a bit to help compensate a bit. But you'd be better to do a little work on the oil pump as suggested as well. I personally found that new gears and smoothing the bottom/thrust plate with (320 then 500 grit) to remove the grooves helped raise PSI a bit more. At least this all can be done without yanking the engine!

Just my .02

I have a 1970 Buick Skylark with a 71 455. It has a low oil pressure problem. The 455 and 350 have the same basic oil system so the issue and fixes are really the same.

I bought the TA performance oil pump fix, and an adjustible oil pressure kit. Long story short, they helped; but in the end, the car with 20w still idles with 5-7psi oil pressure. However, now the rear main seal is leaking (another design issue). Prior to my purchase of this motor, the PO replaced the timing set.

Honestly, I'm giving you the same advice I'm following - I'm building a new motor for the car. Whether it's the mains or the cam bearings that are worn, getting the motor rebuilt doesn't have to be expensive. You have the right motor to rebuild, put in a slightly warmer cam and that car will eat any 71 and later Buick's lunch (stock that is).