1990 Grand Wag Restoration Oil Pressure Question

[rsturek]

I have question on my 1990 Grand Wag restoration, I have a re-manufactured AMC 390 that I just got running over the past 2 months. The Oil Pressure gauge did not work, so I pulled the Instrument Panel and found a bad solder joint on the Oil Pressure connection. Fixed It! But know the pressure reads 40 psi at idle (seems normal) but jumps to 75 psi when accelerating. Is this normal for the 390? FYI, just did an Oil change, put in 5.5 quartz in, so its not to much oil.

Any feed back would be appreciated.

[freehold]

I have no idea what's right or wrong or up or down, but the rebuilt AMC motor in my 87 Grand Wag has the same gauge issue. My guess is there's something screwy somewhere, because if it's running that much pressure, it should've started leaking oil like a sieve, right?

[letank]

I have question on my 1990 Grand Wag restoration, I have a re-manufactured AMC 390 that I just got running over the past 2 months. The Oil Pressure gauge did not work, so I pulled the Instrument Panel and found a bad solder joint on the Oil Pressure connection. Fixed It! But know the pressure reads 40 psi at idle (seems normal) but jumps to 75 psi when accelerating. Is this normal for the 390? FYI, just did an Oil change, put in 5.5 quartz in, so its not to much oil.

Any feed back would be appreciated.

time to get the manual from Tom' s site and go thru the resistance check up , 1) the oil sender, 2) the gauge

https://oljeep.com/89FSM/89Jeep_FullServiceManual.pdf

Electric service and in the instrument panel section

1989 has the same specs as 1990 for the oil pressure data test

5.5 Qts is OK, the specs is 5Qts, someone did a test and you can put 6Qts... in a 360.... What is a 390? a chevy engine? may be this is why the oil pressure is off... the sender has a different resistance than the 360 OEM

[tgreese]

40 at idle is fine for a new engine, esp. when cold. 75 is a bit high - this is with cold oil? Who put the engine together? What viscosity oil are you running? A 390 is an unusual engine outright, not just for a Wagoneer. I'd expect to only see one in a Pre-71 Javelin or AMX or Rebel. Might be to your fiscal advantage to sell the 390 to an AMC enthusiast and run a warmed-up 360 instead.

Peak oil pressure will be determined by the stiffness of the bypass piston in the oil pump cover. If there is a hot rod part in there, it might have more pressure than you need for a street engine. I'd also compare the readings from the electric gauge on the dash to a good full-sweep mechanical gauge. The dash gauges are known to be advisory at best.

I've never heard of too much oil pressure causing leaks. Exploding oil filters, yes.

[rsturek]

Sorry guys, the motor is a AMC 360, not 390. Fingers weren't working.

[rsturek]

Thank for the input guys!
I have the 90 Service Manual and being an old IT service guy I checked all connections/wiring with my meter.
FYI - When I changed the oil, I put 5 qtz in first and checked the level, looked good. Started/stopped the motor and as I expected oil showed a little low as the oil filter fills up after initial start. I added the .5 qtz after and brought the level up to good again. With all my other projects, Ford 302 in a 73 Mustang and a 351 in a 72 Ford Bronco, Oil pressure sits around 40 and fluctuates very slightly. I just thought the 360 had some quirk that causes the big fluctuation? FYI everything on the Motor is new or re-manufactured including Oil Pressure sensor, I repaired the Instrument panel Oil Pressure connection and tested/repaired all the engine compartments wiring harness. As this rig is a complete nut & bolt resto. This rigs harness was in very good shape anyway, just a little brittle in a couple of spots from heat. I replaced or spliced those issue out.

I did recently swap out the 2bbl carb, manifold with a Howell TBI unit and headers, I don't see how that may affect oil pressure?

[rsturek]

BTW - The oil I put in is 5w -30. Not sure what was used during the initial startup of the reman motor. I had a mechanic put the motor in. It has less than 500 miles on it.

[will e]

I would imagine your gauge is a bit off. Only way to know for sure is with a good quality after market gauge.

[tgreese]

...I did recently swap out the 2bbl carb, manifold with a Howell TBI unit and headers, I don't see how that may affect oil pressure?

Not at all, unless it dumps raw gas into the cylinders. Then oil pressure goes down as the oil thins.