Crazy 318 Oil Pressure Question

[Charger71]

I have done several searches about oil pressure and similar posts.  I can't quite solve my problem.

I have a 67 Coronet with a 1974 318 motor.  The original 273 motor grenaded out the side of the block.  The guy I bought it from included the 318 with the deal. 

I engine was cleaned, tanked and baked prior to me rebuilding it.  I put in ALL new internals in the block.   I re-used the heads after getting them cleaned and hot tanked as well. I put a mild cam in it. I even have a 340 intake on the motor.  After buttoning everything up,  I put a Holley 4160 w/ electric choke on it. 

Before I ran it, we primed the pump with a hex drive and got 55 psi with a drill. The oil seemed to be circulating well in the engine.  We got the intermediate gear back in and closed everything up.

It starts very easily.  Upon starting, the oil pressure was around 50 psi according to my mechanical gauge.  I drove it around the block while the pressure showed 50 psi to break it in. It stayed there until the engine got hot and went down to 25 psi on acceleration (1800 rpms) and about 10 psi on idle (800 rpms).  There is some ticking on the top of the engine. I shut it down and am trying to figure out the reason for the drop in pressure.

After searching the forum,  I figure I will check the push rods, lifters, oil pan, oil pump and oil filter.  I have a magnet on the oil pan to see if any particles go there. 

Do any of you have suggestions or solutions for my problem?  Has anyone had the same situation?

I would really like to avoid taking the engine to get more work done. 
Thanks,

Charger71

[The70RT]

Hopefully you did the lower end correctly. Sounds like a bearing clearance issue to me 

[66mopar]

The last time I saw that happen the bearings were ate up.

[craigandlynda]

check to make sure the rocker arm shafts are installed correctly, by the book..they only go one way...and it is a common mistake that affects oil movement

[Charger71]

My son and I have done some checking in the engine.   We drained the oil and found nothing in the oil catch pan.  After taking off the oil pan, we didn't find any metal pieces.  Here is a picture of the pick up tube. (I re-used it in the rebuild after cleaning it) We did have some sludge from the assembly lube.    I thought I had gotten it all out after the first oil change...  We cut the oil filter and didn't find anything, but a oily filter element. 

I also didn't find any gasket maker or anything like that in the oil or pans..

I am certain the rocker arms are oriented properly.  I double checked that.  I have run a drill to pump the oil and got a good soaking on the rocker arms.

Do you think the sludge would cause a problem?   I am using a stock oil pan. Does the pressure change sound like the pump is cavitating?

I am going to ensure the exhaust manifolds are tight for the ticking noise.  I am going to double check the torque on the crank mains.

Once again, thanks for the help.

Charger 71      SORRY ABOUT THE SIZE OF THE PHOTOS...

[The70RT]

I would pull a main bearing since the pan off. Did you plastiguage the bearings upon installation? You could still have clearance problems even with no signs of metal.....so far. Bad guage?

[Charger71]

I plasti-gaged each bearing when I put it together.     My oil gage is a new system including the copper tubing.

I haven't checked the pump to see if the bypass valve is stuck.   Do I have to put a screw or something into the cap on the pump to pull it out?

I appreciate the input with my engine. My son is getting to learn about cars, engines, and problems.   

Would I have any oil pressure if a lifter was out of it's bore?

thanks,
Charger71

[The70RT]

Im thinking the bypass valve should pop out after the clip is removed.    If a lifter came out then yeah no oil pressure. You would have also noticed a miss with that going on though.

[Charger71]

I have to look at the bypass valve on the pump.   The metal cap is about 1/4 inch inside the cotter pin.   I can take the pin out, but I have to figure out how to get the cap out.   
Do I have to disassemble the pump to remove the valve?   It seems I should be able to check the valve without taking the pump apart.

I'll keep y'all posted on our results. 

Charger71

[Chryco Psycho]

are the rocker shafts on with the oil hole down , if they are pointed up that will not help

[Charger71]

Oil Holes are down on the rocker shafts.

Has anyone ever replaced the oil bypass valve on a SB oil pump?

How can i tell if it is stuck open by looking at it? Or does it need to come apart?

Charger71

[62 Max]

When the block was done is there any chance the plug was left out of the front end of the oil galley.? That will give you the condition you have.

[Charger71]

I haven't looked under there, yet.   I am going to put the bottom together and look there.

I know I checked the back plugs.  I can remove the timing cover to check there...  Interesting.

Charger71

[Charger71]

Sorry to keep digging up this dead cat, but I may have found my problem.

I checked several things from easiest to most difficult (costly):
Pushrods - fine,
Oil filter - dirty, but no metal,
Oil Pan - Assembly lube sludge, but no metal,
Oil Pump - Oil Pressure Spring about .0875" to short. (About 5/64")

Do you all believe that short spring would affect my pressure?

I already ordered a new cap and spring to replace the one I took out of the oil pump.   I'll let you know if my pressure goes up with longer spring.  I am also going to use Rotella as suggested by some of you.

Anyway, here is a picture of the short spring...

charger71