Technical Oiling issues on Small Journal 327, no oil pressure at idle

Just busted off the 327 in the Produce truck and I am in troubleshooting mode.
Let me put all the info up front to alleviate the obvious questions.

Small Journal 327, new motor all machine work completed, washed twice in jetwasher and twice by hand with engine brushes and hot soapy water
Scat rods and Forged pistons
Rotating assy spins freely by hand
Melling HV55 Oil Pump with pickup set at factory and welded on. Measures .375" from bottom of pan.
Howards Retro Hyd Roller Cam and roller lifters
Teflon Cam thrust button
Vortec Heads
Pertronix Billet housing Flame Thrower Dist
3/4 Groove Main Bearings
Cam bearing s indexed at 2 Oclock and cam journals in block have grooves
Front cam journal plugs have been tapped and threaded, plugs in place and not too deep
Spin on oil filter adapter installed, new GM relief valve installed
Primed the engine with a drill using a primer tool that fits like a dist to ensure oiling
Hie Gibbs racing break in oil

Now that I have that out of the way, I started the engine and noticed no oil pressure, removed sender and added a mechanical gauge right behind the intake. It has very low oil pressure at idle, like 5-10 psi, crack the throttle and it climbs up to about 50 psi at 2500. As soon as I let off the throttle, I can watch the oil scavenge back out of the clear plastic line. I see some oil on the rockers but not like I want. It dribbles.

I pulled the line completely off the oil gauge and put it into a clear plastic bottle and it is barely getting any oil out of it. It doesn't rattle like it is starving up top and it doesn't knock, so I suspect the bottom end is getting oil.

It has a weird whirring sound coming from the front timing cover area. Sounds like someone swinging a rope. I heard this noise last week, so I pulled it tore it completely down and really found nothing. Changed the timing gear set for one with a thrust roller on the back just for insurance.

Suspect areas:

HV oil pump relief valve stuck open
Spin on adapter for oil filter

Man, I really don't wanna pull this thing back apart. I'm really tired......

 

Valvoline oil?

 

does the distributor have O rings at the bottom where it seals the oil passages?

 

I do not believe so Jim. It is a close tolerance housing. Supposed to be +-.003".
https://www.summitracing.com/parts/pnx-d71000/overview/
It is a HV pump Dave.

 

Did you remove the relief spring before you welded the pick up? You may have lost temper in the spring if you did.

 

I recall something about plugs in the rear of the block , isn't 1 under the main cap ??
dave

 

Did you use plasti-gague when you assembled the short block? If so what kind of clearance did the bearings have? I have seen old tired motors that behave this way with 10 psi at idle. I am of the opinion that 10 is enough as long as it jumps up right off idle. 5 is a little scary though.

The other thing that comes to mind is the oil galley plug under the main cap. Did it get removed? I have never removed one and ran it without but I guess they wouldn't build pressure if that was missing.

 

I didn't weld the pickup tube, it's factory.
I did plastigauge everything. Everything is spot on.
I didn't pull the plug under the rear main cap, but I have wondered if the machine shop did and never said anything, but I think I would have noticed that.

 

I dropped the oil filter, adapter and the bypass valve. Don't see anything out of the ordinary. Oil filter was full to the brim.

 

When you dropped the filter did you put a new one on?

Try a different oil pump or check rotor and cover clearances and the pressure relief valve/spring.

 

You primed it. What were things like then as far as pressure to now. I was priming a 283 once and suddenly the pressure disappeared from sight on the test gauge. Problem, relief valve opened and stayed open. Only by inspecting further inside than from outside will determine your real problem.

 

Not yet. I left everything on the bench. Hoping to stumble on to something without pulling it out. If I have to pull it again, I'm building a run stand first.

 

What filter are you using? Try a different one/brand. That one could be defective or full of assembly lube. It's a cheap and fast place to start.

 

Im gonna say if its not the oil pump and bearings. I would suspect the cam and lifters. You could pull the oil pan and use a tank filled with oil and charged with about 50 pounds of air pressure attach it to the oil guage port and do a leak down test. you will quickly find the source.

 

I had that happen. I bought a used Mallory distributor someone had damaged the sealing surface on, accidently or incidently, anyway the oil pressure was almost zero at idle. ..

 

I called Howard's cams and they were baffled as well.

 

Drop the pan and put air pressure to the pressure gauge port and listen for air leaks.

 

The plug above the oil pump just directs the oil to the filter ,it won't change the pressure.You can check easy enough by putting the gauge at the filter. Too much side clearance on the rods will bleed off pressure quickly.Odd ball lifters or high lift cam can expose the groove when up on the cam. The oil bypass is supposed to operate at 4 lbs differential . Take another one drill out the valve and put a pipe plug in it and see if it changes the pressure. best of luck.

 

I don't think it's bad spring, as that would the opposite effect; good oil pressure at idle and poor pressure when revved up. The fact that you have low oil pressure at idle with a high volume pump indicates to me a serious internal oil loss. The builder of the 327 in my Corvette did me the "favor" of using a HV pump when he did my engine. Not only was the gauge constantly "pegged", but it would overwhelm the drainback system at high revs and fill the rocker arm covers with oil which was forced through the guides causing oil burning. Changing to a standard pump and relief spring solved most of my problems. The guide seals have been compromised and still allow a little oil through. Why do these engine builders do this? A Mellings HV pump is half the cost of a regular one. By using one, they can tell their customers they "upgraded" their build while saving $45.

 

I bought this one because I wanted the welded pickup tube. Otherwise I would have bought a standard pump. I think I have an internal bypass somewhere, but I can't figure out where it is.

 

If you need a new oil pump try the new Melling with hylical cut gears. No more pulsing. Bout a hundred bucks.

 

This one?
https://www.summitracing.com/parts/mel-10550st

 

Just a quick comment on this as this really isn't the issue on this thread. Very true and have had the same fate by my own hand. Took me awhile to figure out why when cruising the street for hours and no problem with oil usage. The Freeway, now that was another story.

 

It took me a few years but eventually I learned high oil pressure doesn't mean longer engine life. a reasonable steady pressure is preferable.

 

Plus there is a hp loss.

 

I'm sure this isn't the issue here, but Melling (had) problems for a while with their pump castings breaking, due know doubt to cost cutting measures.
And yes, the HV pumps have always had the reputation of emptying the pan before the drainback catches up.
Wish I had an answer for you @Roothawg

 

Like I said, I don't care either way on the pump itself. I just wanted the pickup tube set at the factory height, so I didn't have to figure that out. I'll gladly go back to a stock output pump if the problem will go away. I am thinking the pump may still be the culprit. I may throw one in this weekend and see.

 

A high volume pump should not do that unless the relief is stuck. A standard sbc chevy relief is around 60 psi Z28 70psi the relief would open and kick the oil right back in the pan.

 

I went ahead and ordered a stock standard volume pump, pickup tube and oil pump driveshaft from a different company. The first was Melling HV55 and the new one is coming from Milodon. Hoping I can remedy this with a pump change.

 

For yourself more than us. Besure to look over the one in question. Everything, relief valve (both present position of it and the spring), cracks as stated, pump gears, everything. It's the best self learning thing one can do. And if nothing turns up. Well just dig further into the engine. We've all been there.