Low Oil Pressure

[John Milner]

I'm still having issues with my 440.  I installed another camshaft and ran it about 20 minutes.  The engine still has a miss in it.  I don't know if that is ignition related or something else.  The car got up to about 230 degrees so I killed it to let it sit for a while to cool off.  In the mean time I decided to pull some spark plugs to see what they look like.  After replacing the plugs, the temp gauge was back down to about 160 so I re-started the engine.  The oil looks nice and clear.  The engine had about 60 pounds of pressure while breaking in the cam up to the time that I killed it to let it cool down.  When I re-started the engine to see if I had fixed the miss, oil pressure was way down to around 8-10 pounds.  It wasn't knocking or anything but I immediately killed it after it didn't build up pressure.  Could an oil pump lose prime in about a 30 minute time span?  I might replace the oil pump but I'm afraid that I'm going to have to tear the engine back down.  Does anyone with more Mopar experience than I have any suggestions as to what to check?

Everything in the engine was new.  Forged crank turned .020 on the mains and rods, everything was within spec when I built it.  The pistons are .040 Speed Pro forged 6 pack pistons with Speed Pro moly faced rings. If I remember correctly, clearance was around .004.  Cam lube was used breaking in the cam (both times) and a new Sealed Power stock replacement oil pump was used.  I used a factory '68 HP 402 oil pan and pickup.

[justcruisin]

Hook up a known mechanical gauge to the oil then remove the distributor and intermediate shaft, insert a priming rod and spin the rod anticlockwise with a drill, see what pressure you have before you remove anything. Low oil pressure could be anything from a bad pump to a restriction in a gallery or pickup, pickup sucking air etc.

[metallicareload99]

Hook up a known mechanical gauge to the oil then remove the distributor and intermediate shaft, insert a priming rod and spin the rod anticlockwise with a drill, see what pressure you have before you remove anything. Low oil pressure could be anything from a bad pump to a restriction in a gallery or pickup, pickup sucking air etc.

Also check the oil filter, it seems that sometimes they clog up with assembly lube. What did the plugs look like, any single plug really dirty?

...Could an oil pump lose prime in about a 30 minute time span?  I might replace the oil pump but I'm afraid that I'm going to have to tear the engine back down...

I think that is unlikely to happen unless->

...pickup sucking air etc...

Before changing the oil pump it might be worth checking into the oil pressure bypass valve

[John Milner]

I remove the oil pump and took the nut off that retains the bypass plunger and spring. The spring immediately fell out. However, the bypass plunger was stubborn to come out. I whacked it lightly against the palm of my hand and it stayed in place. I got a pair of snap ring pliers and put a little pressure on it and it came out. The picture is how I found it. Not sure if that's the issue but I'll be trying another pump.

[c00nhunterjoe]

There have been alot of pump issues new. Dissassemble, polish and reassemble before even installing. I would have verified with another gauge before ripping it apart though.

[John_Kunkel]

However, the bypass plunger was stubborn to come out. I whacked it lightly against the palm of my hand and it stayed in place.

You should have determined if the bypass was stuck closed or open. Stuck in the closed position would result in high pressure, not low. Stuck open could account for low pressure.

I doubt if it's the gauge since it read OK before the shutdown.

[John Milner]

It was stuck completely seated in the pump kind of as you see it now. Would that cause low pressure?

[John Milner]

The current plan is to install another pump and prime the engine.  If it still shows low pressure, I will try another gauge.  If that gauge also reads low, the engine is coming back out. 

I sure wouldn't think that an engine that had about 60 pounds of oil pressure when it was shut down would spin a bearing immediately upon its next start up. I can't imagine what else would have caused the oil pressure to go down in about 30 minutes of waiting.  I've built plenty of engines and this one by far has given me the most grief.

[justcruisin]

A spun bearing is not going to show low oil pressure.

[John Milner]

Well I had a look under the valve cover and discovered that a lifter popped out of the bore. The lifter is wiped out. The pushrod was bent and the valve appears to be stuck. I'm going to put another cam and lifter set in it, I'll rebuild a set of 452 heads myself to replace these on the engine and try it again. One way or another this 440 will make this Charger live again.

[John Milner]

I finally got the 440 running good.  The problem was the cylinder heads.  The valve guides were too tight and some were sticking.  I purchased these heads with the explanation that they were "ready to go."  I learned a lesson to never install a set of heads that are "ready to go."  I think the heads that I took off of the engine would have worked fine with the guides resized but I decided to go with some 452's.  This time around, I decided to do my own valve job. After I cleaned them up and ground the valves/seats, installed new seals and set up the springs, they went on the 440.  This time around I decided to go with an old Mopar Performance 6 pack purple shaft cam that I had been saving.  I used Joe Gibbs assembly lube on the cam and I also used their 10w40 break in oil.  The engine fired immediately and was ran for about 30 minutes at around 2,000 rpm.  The temp did start creeping up at the end of the break in.  Since then I have dialed the timing in and dialed the carb in and it seems to run great.  The only other change I made was with the oil pump.  I found that my bypass valve had stuck on my "new" oil pump along with all of the other problems that I encountered.  So, I took the one off of my 20,000 mile RV engine that I'm saving.  I opened it and cleaned it all up and installed in on the car.  The car pumps about 80 pounds on warm-up at 2,000 rpm and idles at about 40 pounds.  Now that the car is running good, I can move on to the brakes and a few other small things that need to be done before it can be driven. Thanks to all that replied.  

[TexasStroker]

Glad you got it sorted out...getting closer to being on the road!

[will]

What is the toy in front of the Charger?

[John Milner]

The toy in front of the Charger is a 1930 Ford Coupe. It is on 32 rails, has 32 front fenders and running boards with modified model A rear fenders. 32 grill and headlights. Engine is a 1956 354 Hemi. I'm getting close on it too. I kind of pulled off of it when I bought this Charger and started restoring it.

[Ghoste]

That's a nice ride too.