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Oil Pressure Decrease with Increasing RPM?
https://slantsix.org/forum/viewtopic.php?t=62654		 Page 1 of 4
Author:  Greg Ondayko [ Sun Jul 29, 2018 5:01 pm ]
Post subject:  Oil Pressure Decrease with Increasing RPM?
Hi guys,

This one is somewhat new to me.
It does not seem good.

Hot at Idle ~50 PSI rev to 300RPM 30PSI

Have verified with 2 Mechanical gauges... Changed oil,
Oberg filter - I do need to pull it apart again and take a look in there - I have had it pretty dirty before and it never gave me oil pressure problems.


Adjusted pressure relief valve on Oil Pump - seems to have no effect on the problem..


Gets worse as engine heats up.

Thanks,

Greg
Author:  drgonzo [ Sun Jul 29, 2018 5:14 pm ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
Could the pickup screen be too close to the bottom of the pan?
Author:  Greg Ondayko [ Sun Jul 29, 2018 5:34 pm ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
Quote:
Could the pickup screen be too close to the bottom of the pan?
That could make sense - I had a stress crack in the bottom of the pan edge that I fixed Just yesterday.

That crack could be due to the pick up pressing on the pan?

I welded up the crack (custom Fabbed Pan) but What pickup distance to bottom of pan should I run?


I always (on this engine setup) had the pickup on the bottom of the pan - now maybe that will not work with this block / pickup / pan combo?

Greg
Author:  drgonzo [ Sun Jul 29, 2018 6:50 pm ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
That's a good question. I want to think .25" but it's just a guess.
Author:  Dart270 [ Tue Jul 31, 2018 3:00 am ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
I had this (more minor) when I was using a standpipe and it went away when I replaced the standpipe with an open nipple on the pump. It could be the pickup but it would have to be "sealing" close all the way around. If it changed when you welded the pan, you pretty much have your answer. What about welding a small bolt to the bottom of the pan near the pickup and pulling the pan floor down a bit with a slide hammer?

Lou
Author:  Greg Ondayko [ Tue Jul 31, 2018 4:12 am ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
I opened the filter and it looked normal.

If I recall correctly the pickup was low onto this pan.

I prefer to pull it apart and check and verify the distance. That will be this week's project.

Its easier to cut and reweld the pickup tube a bit shorter as well.

Greg
Author:  Rick Covalt [ Tue Jul 31, 2018 6:26 pm ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
Your running an external oil pump?
Author:  Dart270 [ Wed Aug 01, 2018 4:15 am ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
If stock pickup, then you can put it flat on the floor. You would really have to have it closed off to see flow changes like that.

Lou
Author:  Greg Ondayko [ Wed Aug 01, 2018 8:17 am ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
Yes this is with a stock pickup and external oil pump.


Greg.
Author:  Greg Ondayko [ Sun Aug 05, 2018 8:25 am ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
Got the engine pulled and pan off. Pickup was definitely on the bottom of the pan.

I am going to cut it 1/4" shorter and then reinstall.

Also found some stress cracks in my pan welds on the bottom. Will weld those as well. Hopefully i can get it back together in a timely fashion.

Greg
Author:  Rick Covalt [ Sun Aug 05, 2018 5:29 pm ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
If you plan to have it off the bottom of the pan you may want to consider installing a support brace of some sort. Mine just broke off the threads in the block today, and went to zero oil pressure! I thought about a brace from my windage tray to the pick up just to give it a little extra support when I put the motor together.. Now I wish I had!
Author:  Greg Ondayko [ Mon Aug 06, 2018 4:56 am ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
Hmm interesting.
I could see how the pipe threads cut into the tube would make it a weak point and that would happen.


If that is happening it might be worthwhile to just re- engineer the pick up and put it in the pan similar to a dry sump system - this would be easier for me as I have an external belt driven pump; it's just a matter of taking the pump input / supply line from the plate on the side of the engine to a -10AN fitting on the side of the pan -

I think for now I am just going to try and cut 1/4" out of the pickup tube and get it back togther. This has been a horrible year for the Ruster car.

Rick did that happen at the Mason Dixon event?

Hope there was not much damage to the engine.

Greg
Author:  Charrlie_S [ Mon Aug 06, 2018 5:20 am ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
That is why Chrysler says the pickup should be an interferance fit to the pan. It prevents the pickup up from vibrating.
Author:  DadTruck [ Mon Aug 06, 2018 6:35 am ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
Quote:
the pickup should be an interferance fit to the pan
agree, the FSM for the 83 D150 and the FSM for the 68 Barracuda both describe an interference fit of the
oil pick up to the bottom of the oil pan.

if you want to raise the screen end of the pick up off the floor of the pan, to maintain the interference fit
and the stability that provides, weld shims to the bottom side of the oil pick up to get your desired clearance.
Set the oil pick up depth so the shims make firm contact to the oil pan floor. I am thinking that would be easier than
developing a bracket, although the proper bracket would also work.
Author:  Rob Simmons [ Mon Aug 06, 2018 6:40 am ]
Post subject:  Re: Oil Pressure Decrease with Increasing RPM?
The Challenger engine has the pickup up coming from the side of the pan for the external pump. It also has "shims" welded in four places to keep it about 1/4" off the bottom of the pan.
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