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low oil pressure

Pulled the intake and exhaust manifold. Looked into the head. The valve was covered in gunk and goo. It was the exhaust valve not the intake valve. Quick shot of wd 40 rust penetrate. The valve loosened its death grip. And a few turns with the ratchet on the crank, and it freed right on up. Put the intake back on, and checked prime one more time. Seems to be rotating normally. Going to be stabbing the motor tomorrow hopefully, and checking it out.
 
Got the motor swapped out. Tested it yesterday evening. The Ol CJ7 is alive again. Runs fairly decent. Still have a few odds and ends to sort out. But all in all it'll be a good hunting rig for my dad this year. Oh and after the motor got up to temp the oil pressure stayed around 10-15psi. Is that normal? My yj has a carbed AMC 258 i6 / 4.2l with the same intake and carb as the cj but it runs around 40-50 at temp.
 
kidd79 said:
Got the motor swapped out. Tested it yesterday evening. The Ol CJ7 is alive again. Runs fairly decent. Still have a few odds and ends to sort out. But all in all it'll be a good hunting rig for my dad this year. Oh and after the motor got up to temp the oil pressure stayed around 10-15psi. Is that normal? My yj has a carbed AMC 258 i6 / 4.2l with the same intake and carb as the cj but it runs around 40-50 at temp.
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10-15 at idle when warmed up is liveable..A little higher would be nice but we all know that with bearing wear oil pressure goes down..We use to add a quart of automatic Transmission fluid to the oil a couple of hundred miles before changing it to help free up sticking lifters..To help clean out the combustion chamber we would trickle a quart of water through the carb while running..To boost the oil pressure due to wear you can add a quart of Lucas oil stabilizer at oil change..most of these are old mechanics tricks but they do work
 
I don't know what to tell you except I've replaced everything except the oil pump and my pressure is always hovering around 20-25 and goes as low as around 10. I've added some of the lucas oil additive but it didn't seem to make a difference. As near as I can tell there aren't any issues because of or contributing to this but listen to the smart people on this site that actually know what they are doing if they say otherwise.
 
Thanks guys. I'll try these tricks out and see where they go. I appreciate all the advice :-)
 
kidd79 said:
Guys. What are all the causes of low to no oil pressure in a AMC 258 i6 / 4.2l , besides the obvious no oil, bad oil pump and sending unit that you have run across? I had a rocker arm slide over and the lifter and push rod came out of the head for instance. I'm trying to gather as much info as I can, cuz I have a AMC 258 i6 / 4.2l right now in a 81cj5 that's not making hardly any pressure with a full oil pan. It's got a brand new mechanical gauge, and you can see the oil barely moving up the clear tube while it's running..I just bought the jeep and have no histor on this motor. Looking for a good place to start troubleshooting since I'm out in the gulf of Mexico and won't be home for another 2 weeks.
Thanks.
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Your oil pump could have lost its prime. I have seen this a few times. There are some good treads on priming the oil pump on this site. I had one that I moter I was working on and thought it I must have had more problems than I did after fully priming the oil pump manually all the oil pressure came back. good luck
 
What pressure were you running after prime?
 
Flex BT said:
What pressure were you running after prime?
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During prime I was making 62psi when the oil was cold. It was in the 50's outside that day. After installing the motor initial crank oil psi was right at 60, and while running it to set the timing and check over everything the engine warmed up to around 170ish and I watched the oil pressure drop down while the motor was warning up. It ran fine at temp at 180°@10-15 oil psi
 
kidd79 said:
During prime I was making 62psi when the oil was cold. It was in the 50's outside that day. After installing the motor initial crank oil psi was right at 60, and while running it to set the timing and check over everything the engine warmed up to around 170ish and I watched the oil pressure drop down while the motor was warning up. It ran fine at temp at 180°@10-15 oil psi
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My old Mopar Performance engine book (written by the chrysler engineers) quoted that you would want a minimum of 10psi oil pressure for every 1000rpm so 10-15 at idle warm is livable, the AMC V8 has an aluminum housing around steel gears for an oil pump. aluminum expands more than steel increasing the clearances around the oil pump gears, one of the reasons your oil pressure drops with the rise in engine temperature to me I think you are good to go enjoy your jeep :chug:
 
gert said:
My old Mopar Performance engine book (written by the chrysler engineers) quoted that you would want a minimum of 10psi oil pressure for every 1000rpm so 10-15 at idle warm is livable, the AMC V8 has an aluminum housing around steel gears for an oil pump. aluminum expands more than steel increasing the clearances around the oil pump gears, one of the reasons your oil pressure drops with the rise in engine temperature to me I think you are good to go enjoy your jeep :chug:
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Thanks gert!:chug:
 
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