SBC & oil pressure at idle

[Belgian1979]

The standard block that I have rebuild and is set on the side to pass tech inspection was sent out to the dyno to get tested. I have a standard (plain) oil spring in there. The shop called me to say they didn't want to test it as the pressure was only 38 psi when running the pump with a drill and cold - oil is 15W40 Driven. Not sure if that's what is to be expected. Think a drill only creates about 600 rpm, so this might be correct. Untill now, have only used high pressure springs and those create about 70 psi.
What do you think?

[steve cowan]

The standard block that I have rebuild and is set on the side to pass tech inspection was sent out to the dyno to get tested. I have a standard (plain) oil spring in there. The shop called me to say they didn't want to test it as the pressure was only 38 psi when running the pump with a drill and cold - oil is 15W40 Driven. Not sure if that's what is to be expected. Think a drill only creates about 600 rpm, so this might be correct. Untill now, have only used high pressure springs and those create about 70 psi.
What do you think?

My dart block with standard oil pump,has 40 psi @ 7500rpm
35 psi with vac pump.
Does not lose oil pressure after a pass,cut filter after each meeting with no issues, I would run it no problem

[rebelrouser]

The standard block that I have rebuild and is set on the side to pass tech inspection was sent out to the dyno to get tested. I have a standard (plain) oil spring in there. The shop called me to say they didn't want to test it as the pressure was only 38 psi when running the pump with a drill and cold - oil is 15W40 Driven. Not sure if that's what is to be expected. Think a drill only creates about 600 rpm, so this might be correct. Untill now, have only used high pressure springs and those create about 70 psi.
What do you think?

I would worry you have an internal leak somewhere, maybe the plugs behind the timing gear? I have rebuilt a lot of mild SBC and most hold 60 to 70 lbs with a drill cold. Stock pumps no spring change. Hot at Idle they may drop to 25 or so no issues with that. All of them jump right back up to at least 45 to 50lbs hot at speed.

[Belgian1979]

Clearances were around .0024-.0027" on the mains, .00236" on rods. Doesn't seem excessive.
Can oil galley plugs work themselves loose? Anyway to check front plugs and plug under cap 5 without taking everything apart?

[Tom68]

38 psi sounds about right for a standard spring, you may still only have 38 at revs too if the bypass is big enough.

Be careful swapping springs between different pumps, you then need to compare the installed length.

[C.A.R.E.]

You mentioned the plug under #5 main. Leaving it out will not drop oil pressure, it will bypass the oil filter but should not change pressure.

[allencr267]

600 = 1200 @ crank rpm
Pump disassembled & checked for freely moving & seats with a click, relief valve?
If their drill isn't going bad and they've done this on more then a few, I'd hafta take their word for it.
VERRY unlikely to be the spring.

[Belgian1979]

Ok, going to get it back, take the pan off and take a look.

[Tom68]

Ok, going to get it back, take the pan off and take a look.

If your doing that you need to do this..https://youtu.be/p3qsQU6grvc..but I'll bet you find you get 38 psi doing it if you have a standard GM spring.

[RDY4WAR]

The relief spring does not increase pressure. It only increases the max pressure at which oil is bypassed.

Your dyno guy is an ID-10-Tango. Take it somewhere else.

I aim for 15-20 psi at hot idle with a max of 65-70 psi. Anything more than that just increases oil aeration and power loss with no benefit.

People put way too much importance on pressure. I care more about how the oil is flowing. You can have no oil flow and excellent pressure. So long as I'm seeing at least 6-6.5 gpm, I send it. For some reason, some people think you need 50 psi at hot idle. My SBC doesn't see 50 psi even at 7000 rpm. It's in the single digits at idle, with a 0W-12 oil, and the bearings look as good as the day I assembled it.

Clearances were around .0024-.0027" on the mains, .00236" on rods. Doesn't seem excessive.
Can oil galley plugs work themselves loose? Anyway to check front plugs and plug under cap 5 without taking everything apart?

With those clearances, you don't need the 15W-40. Driven GP-1 10W-30 would be my choice.

There's no way of knowing what rpm the drill was turning. I don't pay any attention to oil pressure on the drill. I just spin it to get the system primed and oil at the rockers, then stab the distributor in, set the timing, and fire it up.

[Belgian1979]

Yes, this is a stock GM spring.

When I spun the pump, I got a good amount of oil on the rockers (all of them). so I was convinced all was good. Didn't check for pressure as I don't have an oil pressure gauge to do it with and I normally fire the engine up in the car and look at the car's oil pressure gauge to verify.

[Belgian1979]

The relief spring does not increase pressure. It only increases the max pressure at which oil is bypassed.

Your dyno guy is an ID-10-Tango. Take it somewhere else.

I aim for 15-20 psi at hot idle with a max of 65-70 psi. Anything more than that just increases oil aeration and power loss with no benefit.

People put way too much importance on pressure. I care more about how the oil is flowing. You can have no oil flow and excellent pressure. So long as I'm seeing at least 6-6.5 gpm, I send it. For some reason, some people think you need 50 psi at hot idle. My SBC doesn't see 50 psi even at 7000 rpm. It's in the single digits at idle, with a 0W-12 oil, and the bearings look as good as the day I assembled it.

Clearances were around .0024-.0027" on the mains, .00236" on rods. Doesn't seem excessive.
Can oil galley plugs work themselves loose? Anyway to check front plugs and plug under cap 5 without taking everything apart?

With those clearances, you don't need the 15W-40. Driven GP-1 10W-30 would be my choice.

There's no way of knowing what rpm the drill was turning. I don't pay any attention to oil pressure on the drill. I just spin it to get the system primed and oil at the rockers, then stab the distributor in, set the timing, and fire it up.

I think you're right on the ID-10-T unfortunately. They pointed to the bearing clearances being too large, which is bogus as I followed Clevite's .001' per inch rule. My other engine has the same clearances and perfect pressure. I asked them to take the pan off and check the oil pump spring and presence of the plugs below cap 5 but they wouldn't do it, said they had no time. Said, Ok, will collect it. Will not return. Will mount it in the car and start it up that way. A lot of work, but I have to pay them 300$ just to put it on the bench and then found out the oil pressure was too low....I've been in business for a long time already...if I treated my customers like that I would be out of a job I guess.

[BillK]

I asked them to take the pan off and check the oil pump spring and presence of the plugs below cap 5 but they wouldn't do it, said they had no time.

I've been in business for a long time already...if I treated my customers like that I would be out of a job I guess.

I don't know if that is fair to judge them for that. If they are as busy as I am I certainly would not have had time to pull the pan, check the spring etc ?? That really is the engine builders responsibility. Personally I would never have taken an engine to the dyno without pre-oiling it myself first. A cheap $20 oil gauge and a piece of rubber fuel line is good insurance. You really should be doing that anyway before you put them in the car.

I am not a big fan of crazy oil pressures but I dont think I have ever had a Chevy engine that didnt show at least 45-50 on the gauge cold with the pre-oiler so 38 might be a little on the low side ? I just looked a two videos I took earlier this year of a 454 Mercruiser engine and a 425 Oldsmobile and both of them were well over 50 lbs with the pre-oiler and my half dead 20 volt cordless drill. Both with 15w40 Driven BR oil.

[BOOT]

The times that I've checked the oil gauge while priming, I've seen bout 40ish psi with cold oil(used/new) and with a corded or cordless drill. Still one time, thought that I was good n still found a bad cam bearing https://youtu.be/f2fbgn4aYFA So I wouldn't be so confident in cold drill oil psi

[Old School]

Clearances were around .0024-.0027" on the mains, .00236" on rods. Doesn't seem excessive.
Can oil galley plugs work themselves loose? Anyway to check front plugs and plug under cap 5 without taking everything apart?

Your clearances are fine. With the std spring you will have very low oil pressure heat soaked at idle. Mine had 10 lbs. Install the white GM spring 3848911 and be done with it. Been there and done that 50 years ago.