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383 low oil pressure

Good time to have checked rod and main bearing clearance was when you had the oil pan off. Would not have taken a hour to have plastic guaged the bearing and checked the crank.
 
I'm running a rebuilt oil pump, stock replacement Melling parts, on my 440. When hot, oil pressure is around 13psi. It will hit 55psi when romping on it. No issues, no clattering. Deep sump pan with 10w-30. Never had the oil light even flicker, even when racing it.
 
The seller said it's rebuilt .....
At this point I would run a compression test on it just to see what you have.
I know we're talking oil pressure but let's check and see if you have compression.
If it shows up low, you know what needs to happen.
 
Compression or not the oil pressure sucks. Only thing that allows that is crappy clearances. Its still going to have to be addressed compression or not.
 
Odd thing too, is there is no lifter noise or tick or any valvetrain noise and seems to run fine. Think ill jut pull the motor out when it cools down here in North Texas and rebuild it.
 
ZDECKICH said:
The car does seem to drive pretty good and smooth.
Click to expand...
There is no reason to pull out the motor and open up that can of worms. The motor looks good in there now. My guess is the motor will last longer than you. You already know how to change an oil pump. Put on a M-63HV oil pump, fill it with Valvoline 50W VR1 and let's see where you are at. I would bet a Hostess Ding Dong everything is fine.
 
For the price of bearing take care of it if need be. Forget the crook it will be fine. This is not normal for a 383 that was supposedly just been rebuilt. If not between 15 and 40 psi its got a problem. Been building these for 40 years. So forget the BS before it gets expensive.
 
Low oil pressure at idle means oil is internally leaking faster than with factory clearance. Where? More than likely lifter bores. Possibly some extra bearing clearance as well. Can you do anything about the lifter bore short of bushing them. Or reaming for a larger lifter? No. Obviously the cam and lifters are happy as the engine runs well. Do we need to worry about extra bearing clearance? Only if the oil gets so thin the pump cant keep up to provide a film between the crank and bearings. The answer? If you want higher idle oil pressure for a given oil viscosity? Then you need to flow more oil. Simple solution. Install a high volume pump that has been suggested. Take it from guys that race these things. We know what works. Maybe you should look at the guys giving info. You might find out they are pretty knowledgable. Rick Seeman
Doug
 
Hey guys, installed a high volume Mellinh high volume pump today part#MEL-M63HV. Made almost 0 difference. About 12psi when warm and driving and still shows 0 at idle.
 
Well, so you’re going to have to dig in a bit deeper.

“What I would do”……. Before pulling the engine, is pull the pan and carefully inspect the pickup tube for blockage or cracks(leaks).
If that all looks good, I’d probably pull the engine.

If one of the galley plugs up front were missing, I don’t think it would have any pressure.
If it’s not a galley plug, or a pick up tube problem, it’s generally a bearing clearance issue.
However, I do know of a 440 that some trash go thru the pump that ended getting up lodged around the #2 exhaust lifter bore, which totally wasted that one lifter bore(wore it out about .060”).
Since that’s very near the beginning of the oil circuit in the block, the main symptom it presented was really low oil pressure.
 
Wow, this is much less pressure than when you started this thread. I assume the mechanical gauge you put in is saying the same? Something isn't making sense here. When one of these engines has low hot oil pressure at idle it should come up real fast with rpm's. Especially with a HV pump. Something illogical is happening here. I don't consider this wear. This is something different and abnormal. I've torn down wore out engines with all the bearings worn down to the copper and they had more oil pressure than this, so I think it's something different. What, I'm not sure. I keep thinking back to a few months ago when I started a 55 year old Road Runner that had a stuck pressure relief. It made around 120 psi at 2-2,500 rpms.Your car is now making less oil pressure than before. When replacing an oil pump on these, the gasket is a PITA. You are twisting the pump to line it up with the drive and the gasket is giving you a hard time. If the gasket somehow gets wadded up or not perfect it can suck air instead of oil. If you leave the o-ring off of the part of the pump that sticks into the block it can suck air instead of oil. Either one of these things would have symptoms like this. Because it has less oil pressure now I have to ask. Did it go together ok?
 
After you answer post #53 I have my next idea. Assuming there is oil in the pan, a new HV pump pumps a massive amount of oil. I'm thinking pull the distributor and prime the oil pump with a priming shaft and an electric drill. If that thing doesn't make 70 psi instantly without the engine running either it's sucking air or something kinky is going on. Any amount of bearing clearance or wear can be easily be overwhelmed by a new HV pump and cold oil. Be sure to mark the position of the distributor and oil drive for reassembly. We're gonna find out what's wrong with this sucka.
 
rickseeman said:
Wow, this is much less pressure than when you started this thread. I assume the mechanical gauge you put in is saying the same? Something isn't making sense here. When one of these engines has low hot oil pressure at idle it should come up real fast with rpm's. Especially with a HV pump. Something illogical is happening here. I don't consider this wear. This is something different and abnormal. I've torn down wore out engines with all the bearings worn down to the copper and they had more oil pressure than this, so I think it's something different. What, I'm not sure. I keep thinking back to a few months ago when I started a 55 year old Road Runner that had a stuck pressure relief. It made around 120 psi at 2-2,500 rpms.Your car is now making less oil pressure than before. When replacing an oil pump on these, the gasket is a PITA. You are twisting the pump to line it up with the drive and the gasket is giving you a hard time. If the gasket somehow gets wadded up or not perfect it can suck air instead of oil. If you leave the o-ring off of the part of the pump that sticks into the block it can suck air instead of oil. Either one of these things would have symptoms like this. Because it has less oil pressure now I have to ask. Did it go together ok?
Click to expand...
It went together fine. The gasket came off very easy as it was only on there for a week as this is the 2nd pump in 2 weeks. The original gasket that was on the car the first time I changed it was easy to get off with a blade. All came off pretty easy. Yes both O rings are on the pump, even soaked it in oil as well as primed the pump both times. It went on fine. The pressure is actually slightly higher with the HV pump from according to the mechanical gauge I hooked up. Hot idle its around 5 (on mechanical gauge) shows 0 on the dash gauge. driving shows 16 on mechanical gauge and 12-13ish on the dash gauge.

Also, on a side note. The HV pump is obviously bigger, the bolts went in fine except one (the longest one) I had to take the crush washer off to get it to thread in. Id, assume I need a logger bolt?
 
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Could someone have installed a cam bearing wrong. Also for those not knowing BB and RB engines oil from bottom to top. So yea the cam and lifter are the last thing to see oil.
 
I use 1 3/8” x 4-½” bolt and 3 ⅜” x 2-¾” bolts on the M-63HV. Those might seem more than 1/4" longer but I like to use all the threads. So it might get crunchy at the end since a bolt may not have been screwed in there in the last 55 years. Remember a bolt is measured from under the head to the tip.
 
Electric gauge? Wrong ohm sending unit? What's a mechanical gauge read?
 
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