Problems With Oil Pressure

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cosgig

cosgig

MoBro Inc.
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Howdy gang, cosgig here!! I'm having a little problem that I'm lookin for insight into and thought I'd bring it to the people's!!

I have a 74 Roadrunner with the original 318 and auto trans! The motor has been completely rebuilt, although the receipts are completely faded and I basically can't read what was done or put into the rebuild! This motor fires right up, idles smoothly, is strong and responsive, and according to the dash oil pressure guage has plenty of pressure! No noises or clatter from the motor....until the motor warms up! I was in the drivers seat last night and noticed that the oil guage took a nosedive right to zero and the lifters started to make some noise! This has now happened a couple times, quiet and lots of pressure until the car warms up, then clatter from the valve train!!

Is is possible that the pump has a seal gone that allows the pressure to drop to zero after warm up?? Could it be the shaft hex stripped on the drive end of the shaft?? I'm getting this car ready to sell and really don't want to bust into the motor!! Any input or I sight would be much appreciated! Thanks, Geof
 
I have found that the cam bearings hadn't been replaced in a couple of motors that we're doing just that or maybe the little galley plugs were left out behind the cam plate. Kim
 
When I worked at the Ford dealership, customers would remove the thermostat ( mostly high millage F150s ) so the 5.0 engine would maintain decent oil pressure long enough to do a trade in deal. All good until you need heat.
 
Very FIRST thing I'd do is "suspect" and check for oil dilution, such as fuel pump, or maybe "lots" of startup attempts, etc, and suspect what it's got in there for oil.

Might be as simple as they didn't replace the oil pump in the rebuild.
 
Hope it turns out to be something not too serious. That RR is cool & will be really nice fixed up!!! :)
 
Well all, I hooked up a remote oil pressure guage and checked the pressure both hot and cold!! The results were NOT promising! Almost zero at idle, and just about 25 at high idle! However, after Dels recommendation to check the condition of the oil, I decided to just change it, it smelled like old gas so I'm going to assume that at least an oil change will help! The good news is that the pressure did not drop to zero as the dash guage suggested when the motor warmed up!

I'm also going through a few other things such as the cooling system, and the kickdown wasn't hooked up so it's not shifting! It has the one piece kickdown for a 2 bbl so I'm changing it to the 3 piece 4bbl stuff!

I'll keep you all posted after the kickdown is hooked up, im going to warm it up again and check for drivetrain noise!! Thanks for all the input people, I really appreciate it!
 
If the pressure is suddenly dropping after a time, I would also suspect that there is a lot of crud in the bottom that is being slowly sucked up and eventually blocking the pickup. It can fall away after the engine stops for a while. I had exactly this with a /6 that had run for several years with a carb leaking into the intake and putting a lot of gas in the oil. The gas and oil mix tending to carbon and crud up very badly.

I'd be pulling the valve covers pronto to look for a lot of crud in the engine, and if was there, then pull the pan.
 
Ok people another update!! After the oil change the car now does not have the clatter that it had, so thanks to Del for that suggestion! The kickdown is also hooked up now, and the trans does shift, although it still needs adjustment! One step back tho, it quit starting with the key!!! When it cools down im going under to check the NSS, it looked highly suspect, and never started in neutral from the get go!

Ah, the fun of the early stages of a project car!!! Thanks for the replies all!!!
 
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