Hot Rods "New" small block oil pressure

So I put a gauge from autozone on the motor and Turned the oil pump with a drill. While the drill wasn't anywhere near full speed because of the load, I got 20-30 psi. I ran the motor, and I seem to get 10 at idle and it shoots to 20 if I give it a little juice. Obviously this isn't right. The motor is rebuilt, I can see plenty of evidence of that (assembly lube, clean internals). No paperwork. No idea what to make of this. when testing with the warning light sender, light bulb INSTANTLY went out when I primed the pump, leading me to think maybe the gauge it's reading right. There is air in the line of the gauge. It's the clear plastic line and I can see air and oil. I "bleed" the line by loosening the nut on the gauge and letting oil go to it, then tightening. That got me higher pressure like 20+ at idle. What do you guys make of this? I only ran it for a few seconds at a time

The other thing, priming didn't get oil to the rockers, but running it for 10 seconds got oil up there. One really oozed a lot of oil.

Thanks in advance for the help

 

It does not sound right.....
Did you assemble the engine?
It could be missing a plug at the front of the cam area in the block and leaking pressure into the timing chain area.
So many variables here, but that initial pressure is low.

 

I am wondering though - the indicator light sender indicates instant pressure over 20. And the air in the line to the gauge??

I didn't assemble it. How could I check this plug you suspect?

 

And having run it for a few seconds at a time at 10-20psi, i
Couldn't have damaged anything right?

 

No I do not think you have done anything to damage it yet, but it is NOT right.
To check the front block plugs the timing chain cover has to be removed.

 

Doesn't that mean dropping the pan

 

Did you use a oil pump primer tool or something else? The correct way to prime the engine is to use a tool that resembles the distributer housing. Otherwise there is no way to get oil to the lifters.

The idiot light will go out with as little as 5 psi, so I have read.

Air in the line shouldn't matter, but you could try another gauge.

Yes, you will need to drop the pan to get the timing cover off, plus pull the balancer.

20+ psi is fine at idle, 30 would be about max IMO. If the pressure continues to build as engine speed increases, you should be fine.

What weight oil?

 

depending on what year of engine you have,yes you may have to loosen the pan to get the timing cover off. A reason you may not get oil the the rockers when you prime the oil pump would be the position of the lifters in their bore holes. Because they are not moving when you prime,,oil won't go into the lifter and up the push rod.

 

Odd that I wouldn't get a single one though. Once I ran it, it did ooze oil from a few.

I used a proper priming tool. Boy this is an unexpected headache. Any chance it's a bad pump?

And it's 1973 by the way

 

10 psi at idle is fine, nothing would be hurt at all. I wouldn't expect oil to the rockers while priming it, the main point of priming it is to get oil disbursed through the suction line to the pump, a full pump, from the pump to the filter, to the main galley and to the bearings. Priming the engine is nice, but it certainly is not necessary, I can't tell you how many engines we built in heavy equipment that did not get primed before firing them up for the first time. I'm talking much larger diesel engines putting out much more power than most any SBC, and costing far more. We primed them when we could, but certainly not all of them, and we never had a failure. It doesn't take long at all for oil to get picked up and distributed out through the system at even a low idle, you should see pressure at the gauge within seconds. I think you may be imagining a problem that doesn't exist.

 

What weight oil do you have in there, and did you put any zinc additive in with it ? (not that the zinc has anything to do with oil pressure.) A 1973 engine needs zinc to protect the cam lobes.

I would drain the oil and put in 5 quarts of Lucas Classic Car and Hot Rod oil in 20-50 weight and see what happens. You haven't hurt anything yet, 20 psi is just ok, but barely.

Oh, and you aren't running a Fram filter, are you ?

Don

 

Thanks guys.

Wix filter, 10w30 Brad Penn oil. It's a high zinc oil for old school motors. Flat tappet and such

There is no way this thing can be ok at 10 psi though... My old stove bolt (dipper) did 15 when it was cold

 

What is the oil pressure at different engine speeds? It should have at least 20 psi at cold idle, and at least 40 when you rev it up when it's cold. The air in the oil presure gauge tube should not affect anything, btw.

If it's a fresh engine, you want to run it at a fast idle (2000 rpm or so) for a while to help break in the cam.

 

Well if I ref it slightly it shoots past 20 but idling it starts out real low then creeps up over a few seconds to maybe 12-15, which is why I am worried. Cold should mean more pressure

 

Stop worrying, fire it up, run the cam in and see what you have. You know you've got oil pressure, you know its coming to the top of the engine, run it.
My high zoot 327 has nearly 100,000 on it, 15-40 diesel oil, when hot, idle around 10-15 lbs pressure, 30 at speed. I think you're expecting too much, you haven't run it yet.

 

Have you tried another gauge yet? You say the one you have has the clear plastic line, which is a sign of a cheap gauge. Try another better gauge and if it reads the same, then you may have a problem. I had a boat with a 260 Mercruiser that I got real cheap because of low oil pressure; I fixed it with a new gauge. Much cheaper than a rebuild.

 

Well I can't run it for a while yet as there is not radiator or fan or alternator. Now I am not sure I want to put the front clip back on until know for sure

I have another gauge I can try its new but no higher quality. What's the chance of two bad ones though right?

Lastly I did turn the oil pump backward with the primer for a moment (please don't stone me) but basic knowledge of how they work and the fact that it did have oil in it lead me to believe that didn't hurt anything.

 

When priming you should rotate the crank, if you're doing this by yourself, prime, turn crank 90 degrees, prime, etc.

 

With all due respect, what you are saying is correct for an engine with 100,000 miles, but since his engine is supposed to be newly rebuilt, he is right to be concerned

 

Ok is this a fresh rebuild? If it is you take the chance of wiping out the cam by letting the motor idle for a short time. If your seeing 40psi that's not too bad to run, just seems low if it's a fresh rebuild.

 

It was supposedly broken in on a Dino

 

I run right around 15 psi at a 950-1000 rpm idle in park, 45-47ish hot at 7000. Stock pump with anti-cavitation grooves and the end clearance held to .002, exit passage and the entrance at the main cap is cleaned up and radiused, new stock spring.

 

Stegosaurus? Triceratops??

 

If it was run on a dyno, you're worrying for nothing. It hasn't wiped out anything, it's got pressure, running it for a minute is just enough time to make you worry, put the car together, fire it up, get the paint on the headers to burn off, tune it and watch it to see where its at. If it doesn't make weird noises, you'll probably be good.

 

Indy is right on the priming proceedure if you want oil up at the top of all the rockers as you have to pump some of them up to get it to move the oil to the rockers , also air in the line does lower the readings ,
You should purge the lines like you have by breaking the connection ( loosen it a little but not all the way ) at the gauge then let it bleed out while its running then tighten it up , air is compressible , oil is not ! and the gauges will read low ,
a cheap gauge will read with a error factor its worth the extra money to buy a good SW or Autometer ( not autogage as that the cheap line ) oil pressure gauge , also your tap should be up by the distributor not by the oil filter or front of the block , and if it has assy lube in the motor sometimes it will plug up the pressure ports till it gets warm then melt out giving you a true reading . but 10 psi at Idle with a stock pump is a little low but your idle speed should be 600-750 rpm and the pressure 20 psi for stock warm ( should be about 30-40 cold) , I doubt its a HV pump as at idle they are 60-70 psi cold .

 

How does air in a line make pressure go away? Just curious. If this is true, then my boost gauge (and your vacuum gauge) never read accurately!

 

OH and idiot light switches are ussually set in the 4-6 psi range , unless you have a switch with a known trip pressure and those are ussually the $$$ ones ( longacre , hobbs ) remember the oil pressure gauge is your lifeline , don't trust a $$$ motor to a cheap gauge .

 

air compresses and acts as a cushion as your compressing a bourdon tube against a gear that moves the needle , a liquid will not compress and reads more accurately as the oil will work against the tube , as for boost gauges they are designed for air pressure and set sensitive plus some are dampered , hook one up to a 30 oil line and you can severly damage it or destroy it , when we overhauled trucks and replaced the motors , we were told to bleed the lines , if you didn't ( and they were hooked with stainless /teflon flex lines ) the gauges would read 10-15 psi low .

 

Wow, I guess physics doesn't work like I thought it did. Interesting. I've never bled the metal lines to any of my oil pressure gauges, and they all read like I think they should. Maybe if I can't see air bubbles, they aren't there?

Strange.

 

oh the lines length on a tractor is about 10-12 feet long , thats a lot of air to compress . the new trucks they use no mechanical gauges , everything is electric and on the block as the computers store the info incase of a failure and they want fast accurate readings ,

I should mention the boost vac gauge on some brands the bordon tube is not put thru a gear set , but instead the needle is hooked to the coil thru a spring and