No oil pressure

[ouvw2]

I’m usually pretty good at rebuilding motors but now my situation has me puzzled. I just rebuild my 1971 and I have no oil pressure.
All the gallies have been taped plugged cleaned and sealed. New 36 mm oil pump from cb performance. It has a add on 1.5 qt sump with welded pick up tube. Cleaned and reinstalled piston in oil temp valve. I believe I have did everything I could do and still no oil pressure on a fresh rebuild.
The only thing else I could think of is the oil pressure valve by the number one piston is bad. What do you guys think? I’m running out of ideas. Knowing my luck it’s something small that I missed. Thanks for your help.

[wreck]

o ring on the oil pick up where it goes in to the case ? drive tang on the pump not keyed into the cam . I'm guessing it's a typo and a 26mm pump ?

[66brm]

Smeared some grease on the pump gears to help prime it?

[Piledriver]

MUST check/set pump drive tang depth and check pump<>ca clearances, with case on the halfshell preferably,
as well as port alignment and pump to case fit. (dont let the pump be the end play, give it a mm or so, I even polish tang and radius end to ~match cam

The pumps are made for t1s: usually needs some love to fit right in a t4.
Frequently bits hit the cambolts and need ground off the pump.
shaft in drive gear may need pushed toward cam or away...
Right oil pickup for case? late is shorter (noticeably)

Is there a piston and spring in the secondary relief? (replace spring with solid spacer if you can)
Primary?
Oil in sump? (would not be first time for that)
Not at odd up angle?
A t4 can take ~5 quarts. (close enough)

I usually initial crank with a loose or pulled idiot light, aids prime//lets the air out, if oil gets that far it will get to the bearings.
(dont let it start, this just insures instant prime)

[ouvw2]

Sounds like I will be splitting the case again. Pile please explain the reasoning behind the solid spacer behind the secondary relief spring. I’m assuming it to keep the oil on the bearings at all time and not in the sump.
Thank for all the help. I will keep you up to date

[Piledriver]

The secondary relief is not required.
It also bleeds a little oil continuously due to a small hole drilled in the piston...
The hole is arguably a feature as it gives air a way out short of passing by the bearings...
The later cases did away with the secondary relief entirely.
Jake Raby suggested the spacer as a simple way to eliminate it.

[wreck]

before you pull the engine out and down , remove the pump cover and see if the gears spin free ,indicating an issue . before that ,you can also over fill the oil ,above the level of the pick up where the pick plugs into the case . If it gets pressure , then you know the pick up is where to look . If it's pump related you can fix that without pulling the motor down .

Nothing worse then pulling something down and then not finding what you thought was the problem .

[Eddie010]

The secondary relief is not required.
It also bleeds a little oil continuously due to a small hole drilled in the piston...
The hole is arguably a feature as it gives air a way out short of passing by the bearings...
The later cases did away with the secondary relief entirely.
Jake Raby suggested the spacer as a simple way to eliminate it.

Ok sounds reasonable, but how do I see that spacer…? piece of solid als long as the spring.
This is new for me, so like to know more..
in the process of using a dual spring case... so need some extra knowledge .

regards eddie

[ouvw2]

Thanks wreck for the advice. Definitely doing it your way. I’m with Eddie, a little more detail is needed for me as well just to make sure I get it right the first time. Thanks to all.

[Piledriver]

Pull the idiot light switch, crank it with the coil wire pulled, or preferably the plugs pulled.
You should have an oily mess in 2-3 seconds given a good starter...

As to finding the correct spacer length I had some small tubing in two sizes, smaller slid into next size up...
I cut a couple bits using the advanced TLAR method, slid them together with a bit of squish from pliers, pulled the spring, and reassembled with the telescoping brass bits.
Disassemble, measure, cut bit of aluminum rod a few thou longer, replace spring, done.
It probably took longer to explain than do.

[ouvw2]

Ok everyone I knew it would be stupid easy. Never use a stock type oil pump cover on a full flow oil pump. This is what happens when you are in a rush And tired when building a motor. Thanks everyone for your help.

[wreck]

Ah , that explains it . easily done . even the most experienced mechanics have brain farts from time to time . Just some are never man enough to admit it !

[raygreenwood]

Also note...just for the record....as Piledriver noted....the secondary relief was done away with on the later cases....but NOT just because its was bad .

The later cases are specifically HYDRAULIC LIFTER CASES. And there was also a feature added that duped main oil cooler pressure relief oil right back to the pump ickup area and not just generally into the sump.

While the secondary relief valve under cylinder #1 is a pain....I do not YET say get rid of it. It is not actually a secondary relief. It is the overall oil control pressure valve. Its function is the proverbial putting the "thumb over the end of the garden hose".

Oil pump is the starting end. Control valve is always the dead end....which would be the control valve under #1. The oil cooler pressure relief valve intersects between these two points and its MAIN function is simply to protect the oil cooler when the oil is cold. And...it does that.

However...once the oil is warmed up...one might say that in some situations the oil cooler relief valve is letting too much oil bypass.

Meanwhile....the pressure "control" valve under cylinder #1....i will be the first t say its poorly designed and executed for it function.

I think it should be MODIFIED to work better and not deleted. Because:

1. ....its not clear whether its spring pressure is actually producing the control pressure its rated at.

2. While having a little but of bleed....a tiny amount....is good to keep air out of the end of the system.....it has too much. And, if its the end of the line and it had NO air bleed.....it would bleed anyway once pressure spiked. It would bleed to the case so it would have no issue.

3. The method they used to make this control valve....is poor. A flat faced piston atop and undersized (to the piston) hole....has no positive seal. After shut down...its a drain down point. At low oil VOLUME...like at low rpm....its nothing but a pressure LOSS point.

I think something like ...first....starting with a smaller orifice....then...either a piston with a pent tip that literally plugs the hole and is not forced out of the way until pressure/volume reaches the correct level....or a ball check valve. Either one should have an adjust screw through the outer plug to adjust spring unseating pressure.

Yes...I remember Jake commented and worked quite a bit with regard to this valve.

I think once this pressure control valve is gotten under better control....better and finer adjusting can be done to the oil cooler relief valve.

Ray

[Piledriver]

IIRC Racer Chris routed the oil cooler bypass oil back to his dry sump tank, and stuck a Parker adjustable pressure relief into the main oil galley and returned that to ds tank too. Of course the (modified) cb ds pump he used ha a 21mm pressure stage, but he played with oil pressure some likely to save power... I suspect the small pressure loss of the relief hole in the piston was nbd with factory pumps that actually fit properly.

I bought an adjustable Swagelok unit in 3/4" npt naval brass, internally adjustable for same purpose figuring thats not really something you'd adjust once set up. had ~3/8" orifice and viton seats, ~1/2" ball, was ~$35ish 15 years ago, probably with customer discount.