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Old 12-07-2021, 05:48 PM
mwood65's Avatar
mwood65 mwood65 is offline
258 I6
Join Date: Jul 17, 2017
Location: Payson Arizona
Posts: 477
Oil Pressure?

I was wondering what the general consensus is on what oil pressure is in the safe limits?

Got the gauges in my 74' Cherokee (258 engine) and at idle it is 20psi and going down the road at around 2500-3000 rpm it has 40 psi.

I thought that was ok but what do you guys think?

Need for concern?
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Old 12-07-2021, 06:37 PM
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Tripwire Tripwire is offline
hey,does anyone here know how to.......
Join Date: Jul 30, 2000
Location: WA State
Posts: 4,656
mine aint that good.....probably 10 PSI at idle if im lucky and 20-30 on the highway....have a tired engine, IIRC the least you should have is like 10 PSI for every 1K RPM ????
Abort? Retry? Ignore? >

86 GrandWag. Howell fuel Injected 360. MSD Ignition + Dizzy. 727/229 swap BJ's 2" Lift and 31's

88 Wrangler 4.2, Howell TBI and MSD - Borla Headers w/ Cat-back + winch and 31's AND a M416 trailer (-:
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Old 12-07-2021, 09:25 PM
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backroadin' backroadin' is offline
350 Buick
Join Date: Aug 11, 2004
Location: Vermont
Posts: 1,099
These jeep sixes were known for low oil pressure. Having 20 at warm idle is pretty good. They might not have had that when new!!
Many a 258 is still tickin' tho, even with lousy oil pressure.
4.0's weren't a whole lot better either.
"Roads? Where we're going we don't need roads." -- Dr Emmett Brown

"When this baby reaches 88 miles per hour, you're gonna to see some serious sht!"

73 Wagoneer - 4.6L Stroker (yeah baby!!) t176/d300, 3.73's, 33" muds, 4"spring lift, 2" body. Offy dualport w/ Quadrajet, pertronix, flowmaster.
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Old 12-07-2021, 10:37 PM
mwood65's Avatar
mwood65 mwood65 is offline
258 I6
Join Date: Jul 17, 2017
Location: Payson Arizona
Posts: 477
Thanks guys,

You said what I was already feeling but wanted to make sure.
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Old 12-08-2021, 05:35 AM
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Brynjminjones Brynjminjones is offline
258 I6
Join Date: Jun 11, 2017
Location: Derby, England
Posts: 473
Hey, that's the same (if not better than) I get from the newer 4.0 I6 in my '98 XJ Cherokee!
1991 Grand Wagoneer - Hunter Green. All stock. Rebuilt 360, .030" over with Melling MTA-1 cam.

1998 Cherokee (XJ) 4.0
1997 Grand Cherokee (ZJ) 4.0
1974 Ford F100 390
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Old 12-08-2021, 08:22 AM
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Old Ironsides Old Ironsides is offline
258 I6
Join Date: Jul 06, 2014
Location: Santa Barbara
Posts: 435
Super Low

On Ironsides, it is only 2-10PSI at idle, and 20-25 on highway, depending on how hot it is At some point, I'll do the pump mod. Its been this way for at least 10K miles.

Old Ironsides: '76 J-10, 401 (1406/2131/DUI/RV Cam), TH400, Part Time, 3" lift, 33s, 346K Miles
Ironsides: '75 J-10, 360 (1406/2131/MSD), TH400 QT, 6" lift, 33s, 110K Miles
'77 Cherokee Chief, 401/Th400, QT, 4" lift... Totalled
'79 Wagoneer, 360, TH400, QT
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Old 12-08-2021, 10:26 AM
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tgreese tgreese is offline
Join Date: May 29, 2003
Location: Medford MA USA
Posts: 11,637
I'd say 20 at hot idle and 40 on the highway is good, really good. The old rule-of-thumb is a minimum of 10 psi for every 1000 RPM. This puts you well within the safe operation envelope. You should not be winding out a 258 anyway - the stroke is very long which makes torque peak at low RPM, and puts a lot of force on the rod bearings at high speed.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
ECO Green: '15 FCA Jeep Cherokee KL Trailhawk
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