NO OIL PRESSURE.

I'm hoping someone can help before i tear down the motor.
It's a 283 with no more than 100 miles on it,Last week I drove it to work and the 97's must have been playing up because it was running real rich on the way home ,but the main thing I noticed was my oil pressure reading 15-20 psi.
It did not change in traffic or cruising speed.
Once I got it home carefully,I emptied the sump which had a lot of fuel in it,changed my guage for an after market one and put fresh oil in it.I blocked off two carbs and ran the centre one only to see if I could get the oil to read but this time nothing,so I shut it down hoping I didn't do any bearing damage.
The motor had 40 psi when I first got it in the car and running,it's a fresh mellings pump and new pick-up.
I've since pulled the distributor out to see if the shaft was broke and noticed there isn't much drag on the pump when turning it with a screw driver.
I had a fram filter which I know everyone on the H.A.M.B hates, could that have had any thing to do with the problem???? or is it time to pull it out and change the bearings?
I was going to drop the steering and take the sump off to check the pump and pick-up first once I get over my appendix opp that I had this week.
Anybody got any advice on where to check first????
It's frustrating enough having to wait till I'm a little less in pain.

 

did you loose oil pressure over time, or did it go from 40psi to 15-20psi almost immediately.... i could be wrong, but i seem to recall smaller displacement chevy SB's naturally have lower oil pressure.... is the melling oil pump a high volume? could be sucking all the oil out of the pan at high rpms.... how fresh is the motor? if you were running w/o oil for a period of time, the lifters would clack... and the cam would have probably gone flat. if you didnt feel a dramatic loss in power, chances are you are in the clear..

quick way to check for grinding... drain the oil and run a magnet through it, or stick one of them engineers magnet pens into the drain hole to look for excessive metal flakes

 

I built the motor over the new year.New pistons,rings,bearings,cam,lifters,oil pump,everything.The pump came with two springs,I put the weaker(standard spring )in it and it went 35- 40psi on fire up while running it in.I only noticed it down last friday after playing with the carbs all week,reading 15 or so on the way home from work, there was no loss in power just that black spark plug feeling which I had to clear at the traffic lights.the oil I drained looked metal free but stunk of gasoline I shall go and run a magnet through it now.
Thanks.

 

If You had pressure ( even if a little low) before changing gauges, and now You don't have any I would hook up the old gauge and check it again, are You running electric or a mechanical guage? maybee You've got a bad bypass spring in the pump its self, anyway I check that guage out first thing. Von Doc

 

doc has it, if you havent drained the oil, go ahead and test out the old gauge... shot in the dark, but can oil be get thinned out from large amounts of fuel in it?

 

Yes....very thin but the pump should pick up new, thick oil on start-up. Were the lifters clicking? I think I'd take out the 1/8" pipe plug at the front of the block [just below the intake] and pump it full of engine oil in an attempt to get fresh oil to the pump in the event the gauge isn't lying to ya. It's possible it's lost it's prime but I've never seen a sbc get an "air lock" in the oil pump.
Then, I'd use a drill to spin the oil pump in an effort to get pressure without running [and possibly ruining] the engine...Remember...it goes clockwise.

 

ahha, there you go rocky....same shit i did on my engine before starting it... while priming it had a friend read the oil pressure

 

Sounds like your fuel pump has a leak and it's gettin into the pan.had the same thing happen on my flathead. it was a bad fuel pump. changed it and no fuel in the pan.

 

Justs for reference, as small blocks oil pressure when at running temp is 7psi. No we know thast not raelly what it is, but that is what it is designed to run at without problem.

Something to check, and it hasnt been mentioned. On your distributor, you need to make sure there are clean grooves that cut around the diameter of the shaft. There is an oil passage that the distributor has to be able to pass the oil from the left side of teh block to the right side. If you have ablocked passage or craped up distributor shaft, you can have some real wierd oil problems.

A bad spring (as mentioned will also cause low pressure). If it starts at 40, then drops to 15-20, its normal. But its shows cam bearing problems ussualy.

Good luck

 

Once upon a time, long ago and far away, the pickup tube came out of the pump on a small block chevvy. I built up the diameter of the tube with a little brass for a snug fit. When applying multiple solutions to a problem, check for results after each solution so you know which one solved the problem..........or caused a new one

 

Thanks for so many options to look into, I primed the pump before fire up with the drill and it pumped up real quick.
The pick-up was a real snug fit from the start so I'm sort of thinking that's O.k.
Do springs often break in the pump ??? or is it unheared of?
Doc......both guages are mechanical so not much can go wrong there right?
Rocky....... Lifters weren't clicking but I didn't keep it running for to long so not to do bearing damage.That oil gallery in the front is behind the timing case isn't it???how can I check for an air lock???
Lakes Modified.....It's a brand new fuel pump,I hope it hasn't shit itself already!Only running 2 psi to the carbs through a regulator
Is there a relief valve in the block for the filter??
Thanks again for your feedback........

 

yes, mechanical guages go bad. Sometimes a brand new one right outa the box does not work. Try another. or try the first one you had

 

O.K Old guage,back in.....I prefered what it read,it was just easier to see if any oil came up that new cheap plastic line to the new guage.
I think my problem is still deeper though....

 

Well, Skippy...if you got any reading at all, you don't need to reprime your pump.......it's primed.
FWIW, the oil galley plug is above the timing cover but below the intake mounting face on the front of the block, over close to the drivers side. Has a little 1/8th inch square plug but the late blocks don't have this. Sounds like you may need to pull thet sucker apart and have a look.