Low oil pressure problems

[69pistolgripRT]

I have some issues with oil pressure in my '69 440. The pressure has always been between 35-65 when the engine is warm. Lately (over the last 6 months or so) the oil pressure has started to slowly decline. I just recently took the car out and the pressure dropped to between 10-20 at 3000RPM. Obviously, I quit driving. I have had some strange thnings happening too. The gauge actually shows pressure dropping when I am going between 75-85. When I drop the speed and RPMs a bit to around 70mph the pressure shows an increase of about 5. Anything under 2000RPM the pressure drops to about 20 or slightly lower. The car is off the road until these problems are resolved of course, but I am a little mystified by the symptoms. The car has lost no power and didn't get hot. I am running a larger oil pan with windage tray.

Recommendations? Also, I have never had the oil pan off of any car in my life. I don't even know how to change an oil pump. Any tips? I am not an idiot so should have no problems; I just haven't done it before.

Order of operations:

Verify pressure with another gauge.
Change oil and filter.
replace oil pump- never done this before.

What do you think about what is going on?

[Just 6T9 CHGR]

Definately use another gauge as a test.  If you are running a stock gauge & are relying on that for your readings, you will be surprised & relieved to see the psi back to normal if you use a good mechanical gauge to check against.

Good luck

[694spdRT]

I agree with Chris.

I have mechanical gauges and don't even use the stock ones. I use velcro to mount them under the dash and tuck them up behind the dash with another piece of velcro for shows.

As you may know the oil pump is external on a big block so you don't need to remove the oil pan if that turns out to be the problem.

[TylerCharger69]

Not to scare you or alarm you.....but I had the same problem some years back due to a bad crankshaft from a parts warehouse.   The oil pump is extremely simple,  which is bolted to the driver side of the front of the block.  If an aftermarket gauge shows the same symptoms, and it turns out NOT to be the pump, the problem I had was that the machining on the crankshaft (10/10)  was poorly done, which caused my main bearings to lose their crush inside the bearing housings and caps, thus  causing my oil pressure to bottom out.   When the car was cold, it was okay, but once it warmed up, it would go all the way down to like 5 lbs.  I HOPE this isn't the problem you are having, but it's a possibility if troubleshooting shows accurate readings and the pump is not the issue.  A sludgy engine will cause this too, but that would mean it would be that way on a more consistent basis.   Let us know!!!

[JimShine]

It will also be wise to make sure you are not getting any gas in the oil. Just pull the stick and smell it and see if you can smell gas.

[TylerCharger69]

 

[hemigeno]

Not to hit the panic button, but the second owner of my Daytona had the same exact problem back in 1972/3 when the car had only 25k miles on it.  He told me that from Day 1 after he bought it, the car's oil pressure would drop to zero anytime it got up over 3,000 rpms.  The problem was not the oil pump, but that the bearing tolerances had increased to the point that it would not maintain oil pressure at higher rpms.  The engine was just about to spin one or more bearings.  That can be a sign of over-revving the engine for extended periods (as was definitely the case with my car's engine after talking with the first owner - he was quite proud of his high-speed exploits!). 

There are a number of other possible causes for your problem, so don't take that one experience as what must be wrong with your engine.  Better check it out though, but don't be surprised if your dash gauge isn't off, since that sort of low oil pressure problem does occur.

[TylerCharger69]

    That's exactly  what happened to mine....it took a little time, but that crank probably came from an engine that was overrevved  many times, and the machine shop that cut the crank did a bad job with it.  My bearing to journal tolerances were okay, but the backside of the bearings to the block and the caps had no crush in them at all.....A bearing was sure to go before too long.  They should fit tightly in place, and these were quite loose fitting.   They were fine when I assembled, but after a few HUNDRED miles...they failed.   Your symptoms of that are there, but hopefully it's not the case in this instance.

[69pistolgripRT]

Well, I'm not hitting the panic button, yet.

I hooked up a mechanical gauge and the oil pressure started at 75 but within 30 seconds had fallen to around 20. Stayed right around 20 no matter the rpm. I let it run in the drive changing the rpms for around five minutes with little change from the 20.

So, both gauges read low pressure. So much for the easy fix. I checked the dipstick and could detect no signs of gas.

Tomorrow, I will change the oil and filter. If no change I will then try a new oil pump. I guess if a new oil pump doesn't fix it I will hang myself.

Just kidding. But, this is a numbers matching engine in a true RT 4 speed so I can't take any chances with oiling issues. I swear if the engine needs rebuilding I will finally go with the 472 I have been contemplating. I have all my ducks in a row thanks to Chryco and others helping with parts selection. I guess this will be a good reason to store the 440 away. Maybe my wife will buy this excuse.

The 440 was rebuilt about 10 years and 5000 miles ago so there could be an issue with tolerances wearing, I guess. I would hope not but you never know. Anything I else I should look at or just wait and do what I have already listed?

[694spdRT]

Just curious, what weight of oil are you using?

[TylerCharger69]

LOL.....you need an excuse for the 472 to tell the Mrs.  Oh...in that case...your engine is TOAST!!!!....I'll vouch for you!!!   lol..just kidding...It doesn't sound good though so far.....If the pump makes no difference......well......I smell a 472 in the midst!!!

[Chryco Psycho]

check the bypass valve in the oil pump , if the spring is weak or broken or dirt has it jammed open you will have low pressure , the bypass is behind the plug pointing towards the engine mount on the rear of the oil pump BTW