Small Block Ultra High Oil Pressure HELP!

[WAYNES WORLD]

Hello Everyone!
I have a fresh built 273 that idles with 75 lbs of oil pressure using 5-20 oil and will peg the 100 psi mech gauge before 2k rpm.
A little background information:
Rebuilt 66k mile never been apart motor. Decked .010. Stock 2 brl pistons. Stock bore, polished crank std bgrs miked and plastigauged. All clearances in spec. New rod bolts, big end sized, bgrs checked. Assembled with stretch gauge. Blocked was fully cleaned and all passage ways rodded.
New cam bgrs installed by machine shop with many years of Mopar experience. Mild (340 spec) Hyd cam. Custom length push rods.
Modified 302 heads, ported, slightly larger valves, cut .060. Using the original 273 adjustable rocker assemble. New locking adjusters. Slots located down, DS to the ft, PS to the firewall. Banana cuts to the bottom with the tiny holed pointing to the lifter galley.
Melling stock volume pump. (Actually 2 pumps thinking it may have been a pressure relief issue.) No change after second pump.
Autometer mech gauge and also tried a NIST traceable calibrated pressure gauge hoping it was a gauge issue. Surprisingly the Autometer was damn close.
Started out with the 30W break-in oil and had a blow out at the oil filter. Fixed the leak and ran fine but had nearly 100 psi above idle. Concerned with having a pump issue I dropped the pan and replaced the pump. New pump was dissembled, cleaned, lubed and installed. Added new K&N filter. Fresh 10-30 with break-in lube. Primmed right up. Still high. Switched to the 5-20 with the additive.

AF ratio is great, timing good and it runs great but if you tap the throttle up to 4k it spits a bit of oil out the rear main seal.
I pulled the valve covers off to recheck the position of the rocker shafts but they are correct. I have no trace of metal in the oil filters and no unusual sounds coming from the engine. When I pulled the plugs everything turns freely. I have about 200 miles on the motor at this point but nothing has changed so I need to get this figured out.
I was surprised when I took the valve covers off there was absolutely no oil under the cover itself, not even a film. No splash? I removed the DS shaft assembly and it did have oil in the shaft and there is no sigh of wear on the ball/cups or valve tips. They had oil on them.
I’m thinking maybe the cam bearing was clocked incorrectly?

Any ideas would be greatly appreciated.

Wayne

 

[Lefty71]

I’m thinking maybe the cam bearing was clocked incorrectly?

I dont have experience with this, but I was thinking the same thing before I read your whole post. What were the specs on the mains and rods(clearance)?? IIWY, I'd pull it back apart and start lookin.

 

[padam]

I don't see how 1 restriction in the system will increase pressure. All of the other proper clearances should allow pressure to bleed off.

I am thinking that the relief spring on the oil pump should be limiting oil pressure.
That's where I would start.
I know you swapped pumps, but 2 bad parts are not out of the question.

 

[Islandkent]

Same pressure relief valve spring more than likely the culprit. I done a 340 once. It was blowing up the filters like balloons. Change the spring out with a different one out of another pump.

 

[PRHeads]

Many years ago when I was building SB mopars for a local circle track class, the HV pumps were coming with a bypass spring that would produce 140psi, hot, at rpm.
The std M72 pumps we replaced them with would make about 80psi.

I also had a metal shaving get stuck in the bypass and lock the valve in place........ in the fully closed position.
I ended up having to use a 300psi gauge to see how high it would go.
Hot idle was about 125psi.
It’s a good thing I had the oil filter with the extra thick canister on the motor.

 

[beanhead]

Just to re-cap,
You've tried different pumps--no change
The filter blew out, so you've tried a different filter (people have gotten defective ones)
Tried different gauges (which, if the filter blew out, indicates gauge or sender isn't the problem)
You're using a relatively thin oil
Shafts and rockers are correctly installed
Valve covers are dry after running
By all means, triple-check all that stuff especially the filter bypass to make sure they're good. And at this point I would run it briefly with the valve covers off to see how/if the top end is oiling.

If it all checks out, that indicates an internal problem. You mentioned mis-installed cam bearings, that's a possibility. Other clearances may be too tight, they may have used the wrong plug in the rear galley and partially blocked the passage out of the filter, or there may be blocked passages.
I know you said the shop did it right, but unless you personally verified it afterwards, there's a good chance they made a mistake somewhere. It happens. I'd give them a call..

 

[493 Mike]

Pull the rocker assemblies spin the pump with a drill and slowly roll the crank-look for oil flow, both sides.
Mike

 

[steve340]

No oil to the rockers could explain the very high oil pressure. The oil "leak" up at the rockers would certainly drop the pressure.
Has the camshaft got the oil holes in it?
I think I read somewhere the 273 had a slightly different oil system but cannot be sure on that info.

 

[dvw]

I wonder if the core plug that goes up from the pump passage to divert the oil to the filter is set at the wrong depth partially blocking the passage?
Doug

 

[WAYNES WORLD]

I hate to pull it apart but it looks like it has to happen. I'm going to drop the oil pan, pull the pump and the rear main cap to check that plug. Doesn't seem to be getting much oil to the heads. FYI my cam had the full grove around the bearing surface so it's not the pulse oiling. Hopefully the bottom end hasn't suffered any damage.
Wayne

 

[beanhead]

I wonder if the core plug that goes up from the pump passage to divert the oil to the filter is set at the wrong depth partially blocking the passage?
Doug
View attachment 1190400

I also thought (SB gurus help me out here) that if there were threaded plugs in the front--even though the typical thing was to use cup plugs--it's possible to run one in too far restricting/blocking oil to the driver side lifter galley.

 

[steve340]

Looks like you have done a nice job on that motor.
Far better to pull it down again than pick the pieces up with a garbage bag.
Before you pull the whole motor 493 Mike has made a good suggestion.
I cannot remember if it is possible to get the head gaskets wrong so they block the oil holes up to the rockers.

 

[dvw]

Obviously you've had more than one pump. I had a small block oil pump last year with the relief spring cap in backwards. It made 250psi with the drill and bent the oil filter plate.
Doug

 

[Challenger340]

Very sorry to hear of the issue and I feel your pain.... looks like you've done a fine job with the install ? so the thought of another R & R and dis-assembly is not fun.
Nonetheless...
from your posted information and diagnostics I can't see any choice at this point than a teardown and inspection..... with particular emphasis on the Oil System and Internal Engine Bearing clearances present.....
"Within Spec" isn't always optimal for all Engines when it comes to Bearing Clearances.... especially with todays variances in Parts qualities.... I would suggest some "targeting/prioritizing/Blueprinting" of clearances therein may be in order.... Mains @ .0025" to .0027" with no less than .0020" on the Rods approaching .0025" checked with Live Gauges(Forget plasti-gauge).... and of course verification of Cam Bearing Oiling.
Remember.....
Crankshaft Oil 'throw off' is an integral part of Cam Lobe Lubrication.... and tighter Bearing Clearances = Good Oil Pressure but typically less Oil throw off ?

We're lucky enough to be able to Dyno every Engine here before it leaves .... run in the Cam... Tune the Engine, look for any potential problems, etc., etc. ?
But just say'in....
even one run-in stand between a circle of like minded DIY buddies can be a great asset to find problems before installation ?

 

[WAYNES WORLD]

So I pulled the engine down and the cam bearings oil holes are 50-75% blocked due to the bearings being rotated out of alignment with the oil holes in the block. All the rod and mains are good and the cam and lifters look fine. I have decided to build a 360 short block and use most of what I have: heads intake carb, change cam.

 

[steve340]

At least you found the problem.
Why not sort the cam bearings and use the engine?

 

[khryslerkid]

Glad you found the problem. Now did the bearings spin or were they installed wrong?

What's the reason for the 5w 20w oil?

 

[WAYNES WORLD]

The bearings were installed incorrectly, not clocked so the holes didn't line up fully. Good thing was it was caught early and no damage.
I'm selling everything from this motor and putting in a 5.9 magnum.

 

[RemCharger]

Chucking the baby out with the bath water!!