Help, i need a gen v big block chevy expert!!!!

I have a blown 509 chevy engine that I purchased. it was a 502 crate motor and was bored. all componants are new and were done at a reputable machine shop.

My problem is low oil presure. I can only build 20 psi while priming.
I am using a tool with the dist. bushing.
(It has a melling high volume pump)
I started the enging and can only build 20 psi. if i increase the rpm the presure will actually decrease slightly and come back to 20 psi.

I removed the pan and pump. the pick up seems fine .I dis***embled the pump, it loooks ok as well. I checked the suction screen hight as well.

I tryed priming it from a coffe can on the suction screen as well so i could hear any ****ing (air). all is ok.

I removed the presure relief plunger and shimed with a washer, still 20 psi.

so what is it????????????
Geo

 

Try another oil pressure gage.... The one your using might be a bad one.... Let us know of the outcome!!

 

tried another gauge.

 

I'd start the engine and see where you're at @2500RPM. Then decide what to do when it's broke in and hot idling. It's good that you know to shim the spring. That's what I do on every engine. I even put a nut behind it if needed.
On one engine about 10 years ago I forgot the plugs that go under the timing chain. It was a real b!tch finding that boo boo,,but I did and no harm was done.
Let us know how it goes.
Oh does the distributor bushing have the groove that allows pressure to the lifters or does it leak down on the oil pump?
I made mine from an old HEI, so I can flush the galleys before I drop in my lifters and then pressurize them later.
It could be that the rotating ***embly is set up loose for RPM and that leaks down alot too.The cam bearings are new too?

 

sounds like a cam bearing twested when put in. my friends 502 had the same problem
new.

 

Try rotating the crank as you prime..it is just a thought. Sounds likes like something isnt lined up right or it has a m***ive internal oil leak..Timing Chain/ Oil Gallery Plugs? are you getting oil to the top?

 

Where did you plumb the Gauge line into?

 

DO NOT RUN THAT ENGINE UNTIL YOU FIND THE PROBLEM. Get someone that's experienced in that engine and have them dis***emble it if necessary, something is definitly amiss.
Trying to find the problem by asking on here is almost a waste of time. Not to say there aren't any good engine people here, just hands on IS better and there is too much at stake for hit and miss diagnosis.

Frank

 

shouldn't 20 psi be enough to run it?

 

there is a byupas in the block under the two plugs right by the oil filter adapter? look where it is machined for an oil coller and under the threaded filter holder i think is one as well. check into that, ill bet it is the problem...

 

From info that I have gathered for my Gen 6 rebuild:

For all racing/performance applications that will NOT use an oil cooler but will maintain the stock oil filter location, you must remove the center by-p*** valve directly under the threaded oil filter adapter. Removing this valve eliminates three redundant right runs in the oil system. However, if you leave this by-p*** in place the oil system will still function as it was intended, but a loss of oil pressure can result from the four right angle turns required for oil to return to the main oil tunnel. Install only the one byp*** valve that is located next to the threaded adapter.

This probably is not your issue here but, I would make sure the one relief valve is where it should be. I am not an expert, I did this on my motor with a very slight oil pressure rise.

M. McF.

 

That thing should be makin at least 80 to 100 lbs oil presure you got a plug out somewhere. It will live on 20lbs but not advisable to run it

 

A 1/8" pipe plug above the oil filter. (same place as my 427 mark iv)
do not know of any other place????

 

I see a byp*** type valve under the filter.

Where is the other? I see the 2 cooler fittings, do i remove them to find it?

 

I would be looking for loose or missing galley plugs first. Like the ones behind the timing gear. Wouldn't hurt to pull the manifold and timing cover off to have a looksee.

 

May or may not help: http://books.google.com/books?id=XG...wAw#v=onepage&q=Gen V 502 oil gallery&f=false

 

You wil probably need to pull the engine back apart... I had one that the rear cam bearing was not installed correct and only had 20 psi. Installed correct it had 90 psi

 

Yeah it'll live on 20 psi. That's why I mentioned to start it.NOT RUN IT! Especially if it's got a roller cam then you don't have to rev the engine to break in the cam. Just let it idle.
On most of my engines I tap the by-p*** and put in a threaded plug.I haven't had one fail but just do it because it makes sense. A 200 rpm drill motor won't reflect 2000+ rpms. I've seen loose engines idle at 20 and hit 80 at 4000 up,etc. Another thing I've done is remove the pan and sink the pick up in a coffee can with oil and spin the pump and watch the bearings to see which ones dribble and which ones pour. They should all dribble. I've seen scarred cam bearings cause internal leaks. The suggestion to rotate the crank every 90 degrees and see if there is a drop or spike is a good idea.

 

Had the same problem with my 427 BBC. I ended up tearing the engine down and found the machine shop had installed the wrong rear cam bearing. The one they installed was for a 396 with solid lifter cam, and it had a groove in the center of the cam bearing.
I pulled that and installed the correct bearing. It now runs at 45 psi at idle, and around 85 psi at cruising speed.

 

I would not run it at all. Most of the time it is simple thing that is over looked. What are you using as a primer? I had a Goodwrench SBC that gave me sort of the same B.S. but it turned out that my Black & Decker Pecker Wrecker drill was the problem so I fired the engine right up and drove it for another 100K. With a BBC you need to rotate it just to get oil up to the top by lining up the lifter oiling holes to the oil galley port.

 

I found it! The builder/machine shop forgot to install the 3 plugs in the lifter valley

 

fantastic!

 

OOOOOOOOPPPPSS...well at least you found it.

 

Why do builders do that? What else do they miss?

 

There is also supposed to be a rubber o-ring under the rear main cap. make sure that is in place while you're at it.

 

Looks like you've most likely found your problem with the missing plugs. You said it has a Melling oil pump. Check to see if it's a normal pump without the anti-cavitation grooves in the cover and body above and below the gears. The part number will have a "C" suffix if you know the part number. The anti-cavitation pumps are intended for high RPM use only and produce minimal oil pressure - less than stock - at normal idle speeds. The SBC 555-C pump only makes 5-10 PSI at normal slow idle speeds. If this is a street engine, and you have that style of pump, replace it.

 

To be clear - the part number will have the "C" suffix if it IS an anti-cavitation pump.