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How much oil pressure should I have?

9K views 12 replies 7 participants last post by  chrysler300le 
#1 ·
So I added the aux guage to the 77 because I didnt believe the factory guage was reading right, which I guess its not since it takes 5-10 mins for it to read anything at all.  Anyways, got the oil pressure guage in and the sending unit T'd off of the port on the back of the block.  Its reads 20 PSI!!!!!  all the time, no matter if at idle or 3-4000 RPM its just reads 20 PSI and doesnt move.  THe trucks smokes some but I presumed valve seals.  Its a 77 W200 ex m880 with a 318 and 79,000 original miles.....  surely it cant be worn out that quickly.  All my other trucks (94+) with the magnums run 40-50 PSI at idle...  should I be concerned about only having 20 PSI?????
 
#3 ·
10 psi per 1000 rpms is the "accepted standard".  I run 20 at idle and 50 - 60 down the highway depending on the day.
 
#4 ·
Before rebuilding my 360, it would idle with 20 psi, and 60 when driving as well. You might have a bad gauge if it won't read any higher. Is it a mechanical or electric gauge? ???
 
#5 ·
So, basically I need to drop the pan and take a look see.  On a 77 w200 with single exhaust, can I get the pan off without having to take the exhaust loose.  I've never tried to take the pan off in the truck on anything but a 94+ ram.  I was hoping I could do it without having to drop the exhaust....
 
#6 ·
Corey said:
Before rebuilding my 360, it would idle with 20 psi, and 60 when driving as well. You might have a bad gauge if it won't read any higher. Is it a mechanical or electric gauge? ???
I have factory electrical guage + a brand new electrical VDO guage and sender, both read the same, its just the factory guage is sometimes intermittent, but it reads 20 just like the VDO, so I presume that both cant be that wrong, alos neither move a mm when I rev it up they just sit on 20, thats the part that bothers me. I would like to have at least 40 when on the throttle.
 
#7 ·
One last thing..... I have a brand new milodon pump on the shelf I bought to go in my 94 318, does anybody know if the pumps are the same or if it will work in my 77 318 since its not a magnum??  any help would be appreciated... thanks
 
#8 ·
I'd get rid of the electrical model and get yourself a mechanical model. I ran a electrical model in my ram, it was accurate but i swapped it out for a complete set of mech. gauges.

20-60psi is normal for most engines.. my ram's 4cylinder idles at 75ish and spikes at 90-120 at highway speeds. thats the normal for my engine.  But aside from my stuff you'll find that most of the members swear by mechanical gauges for their vehicles, too much can bug out on an electrical gauge (though you may get a faulty mech. gauge from time to time.)

Also i'd check that oil pump, your screen could be clogged shut. it might even be failing.  Something doesn't sound right to me though, that gauge should at least move somewhat when you hit the throttle
 
#9 ·
Electrical guages and mechanical guages only differer from 1 or 2 psi so i dont understand why mechanical would be better.. Do you really care if your engine has 45 psi or 48 psi?
Its basicly the persons preference.

Though i would be concened to only have 20 psi while going 65 on the highway. Time to replace the oil pump, better yet, time fore a rebuild.

I have no idea if there is a difference between the magnum and non magnum pumps.. You could buy a pump for your 77 and compare the two and if they are the same, take it back.
 
#11 ·
I was able to drop the pan on my dad's 74 d300 towtruck without pulling the exhaust.. it's got a Y pipe near the bellhousing to go from duals to single (is that what you're talking)

The only thing you may have to curse at is the crossmember... sometimes they can be fun when you're dropping that oil pan and laying on your back.
 
#12 ·
PatrickH said:
Electrical guages and mechanical guages only differer from 1 or 2 psi so i dont understand why mechanical would be better.. Do you really care if your engine has 45 psi or 48 psi?
Its basicly the persons preference.

Though i would be concened to only have 20 psi while going 65 on the highway. Time to replace the oil pump, better yet, time fore a rebuild.

I have no idea if there is a difference between the magnum and non magnum pumps.. You could buy a pump for your 77 and compare the two and if they are the same, take it back.
If you put a decent aftermarket electrical oil pressure gauge in, it should be accurate enough. The mechanical gauge's advantage is that it's very responsive. If you rev the engine, the oil pressure goes up immediately. The electrical gauge is slower to respond. At least that's been my experience.

I'm pretty sure the pumps are the same. Mancini says they are.
 
#13 ·
Oil pump is interchangable for all LA and magnum engines.  replace your pickup screen.  Depending on how worn out your motor mounts are depends if the crossmember  will be in the way of oil pan removal.  If you have to you can just lift up on engine with cherry picker.
 
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