The Stovebolt Site Forums The Shop Area Engine Shop 1990 350 NO OIL PRESSURE?

Have got a friend that has installed a brand new 350 crate motor into his 69 chevy pick up. It has run for about 3 to 4 minutes with no oil pressure? It has the front oil cooler and later model lines and stuff, hopefully this was ok to post this problem here. He claims that he primed the pump with and old dist..

If he indeed has no oil pressure he has probably trashed the engine running it that long. He needs to tap in a secondary oil pressure gauge and briefly start the engine. If pressure great. If no pressure, he’s in for a tear down and rebuild. Since he’s working on a ‘69 Chevy P/U posting here is just fine.

If the engine was not put under a load or accelerated above idle, he might have dodged a bullet. Try pulling the distributor and repeating the oil pump spin. If there's proper oil flow, the drill motor running the pump should load down noticeably, enough to make the drill hard to hang onto. It's possible the pump drive shaft has failed, or the distributor might not have been seated into the shaft correctly. I've also seen a new oil pump fail to prime itself if it's not packed with vaseline or oiled before installation. Bottom line- - - -at least pull the oil pan and inspect the bearings. If the crankshaft isn't scored, it might be a good idea to change the rod bearings. Mains are usually pretty durable, unless the engine is under load when the oil pressure goes away.
God luck!
Jerry

ol55 Did it knock or screach any ?? If not might be OK should be able to bring the oil pressure up even with a speed handle,we used to do it that way.Some meechanics pack the pump I never did.

Say, the old guy at the parts store told my pal to drain the 5w 30 o and try some thicker oil, like maybe some straight 40 weight until it got pressure. Does that make sense, of course trying the drill motor.

RUN- - - - -do not walk away from 5W-30 oil. It's approximately the consistency of water when it's cold, and it does not get "thicker" as it heats up. Try 15W-40 instead, or straight 30 weight. That being said, simply increasing the thickness of the oil will only hide the problem, not cure it. If spinning the oil pump with a drill motor doesn't solve the pressure problem, open the engine up and check for obvious leaks in the oil circuit. I once discovered the oil gallery plugs behind the camshaft sprocket missing on a freshly assembled 283. That one had no oil pressure whatsoever on startup and wouldn't build pressure by spinning the pump.
Jerry

Well my pal brought home 5 qt. Jug of 20W 50 valvoline would that be efficient?

Yes, that will work, but he's probably just delaying the inevitable. I'd strongly suggest pulling the oil pan and inspecting the bearings unless he's the type who bets big in a high stakes poker game when he's holding a mediocre hand! A little labor now might prevent a disaster later.
Jerry

Thanks there Ol buddy. Only man to drive a frozen whale over the Grapevine.

Had that problem on a early El Camino and found that there is I believe 3 different length drive rods for the oil pump got the right length and away we went!

ol'55 You know whatever oil was in that 350 oil pressure should have come right up. Since it did not the question now is did it damage it someone who understands how to hunt for the problem needs to look at it.once that is done then research the damage factor !

Found the oil pressure problem, now he seems to have an overheating problem with it. All brand new thermostat,radiater, and cap, for giggles he run up the engine which really sounds good, put a vacuum gauge on it and no vacuum what so ever. Now this here 1990 engine has a throttle body on it. I am not sure where he is connecting the hose for the vacuum. Could a vacuum gauge detect an overheating condition? Now as long as he is driving on a straight road no problem but going up a hill look out she starts to get really hot. Thanks there Bolters.

Glad to hear that the oil pressure was resolved, it would be nice to know what the problem was.

Given that this is a new crate engine it would be good to know if the water pump is the correct one for the belt setup. They make water pumps for both rotations primarily to deal with the difference between v-belt and serpentine belts routings that result in the pump running opposite. If somehow he got the wrong pump for his belt setup the pump would be running backward and therefore not flowing much coolant.

Does he have the right fuel pump pressure for the throttle body injection system? Low fuel pressure can result in a lean condition that would be more evident when under load, like going up hill.

The vacuum guage being "0" could be where he plugged it in, throttle bodies don't have a lot of excess vacuum ports like carburetors tend to have. If the vacuum is really zero he has a massive intake leak which would also result in a lean condition and engine over heating.

...is not an acceptable "solution". What was wrong and how was it fixed?