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Author Topic: 304 low oil pressure  (Read 1026 times)
Welds Naked
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Jeep/Vehicle: 2000 TJ
Posts: 17



« on: 04/21/09 - 01:05PM »

Hi all,

I got a quick question for you all. I have a 77 304 v8 that was recently rebuilt. When the engine is cold the oil pressure is high 45-55psi but when the engine warms up its idle pressure is very low like 3-7psi. run the engine up to 1500-2000 RPM and pressure comes up to a normal 35-45psi. I do not have any noise in the Valves. Im new to AMC engines worked on chevy/ford. Thanks for your time.
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TanYJ
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Jeep/Vehicle: R.I.P. My Old Friend '88yj
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« Reply #1 on: 04/21/09 - 01:33PM »

IF the 304s are similar to the 360s, the oil pump is integrated into the timing cover.  When the inside begins to wallow out, you loose oil pressure.  The old waggy we used to own did that.  It ran fine, but made me nervous.  There's a cheap rebuild kit with thinner gaskets that MAY help, but if the inside is wallowed out, the only thng that can fix it is a new cover/pump, & hold your sack when you price that.  Good luck.
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mike4089
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« Reply #2 on: 04/21/09 - 05:09PM »

i ran mine like that for years...it was a 360 however, and it never made a noise or acted funny.  After 2 years i dropped the oil pan to fix a leak and all the cylinder walls looked good some with hone marks still....Id run it, if you do decide to price out a new timing chain cover (which are expensive) check out bulltear.com 
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Willysman23
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Jeep/Vehicle: 47' CJ2A/96' xj
Posts: 39


« Reply #3 on: 06/13/09 - 01:17AM »

New timing covers are like 225 I think.There is an oil pump repair kit that I used.It helped some but not enough.They can run on low oil pressure for a while though,my old 304,360 did that.I would get the timing cover and protect your engine from eventual damage.The repair manual says 13 psi minimum for the 304,360 I believe.
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Jeeper guy
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Jeep/Vehicle: 90' YJ
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« Reply #4 on: 06/13/09 - 02:03AM »

What oil are you running? Mine on my fourbanger was kinda low pressure for a while after recent rebuild, after i switched from the straight 30 weight to regular oil(10w-40) with some lucas it was normal and just fine now... How many miles are on the motor?

Dosent oil pressure have to do with how the oil passes around the bearings and not how much pressue the pump is pushing, just curious?

Alex
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Willysman23
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Jeep/Vehicle: 47' CJ2A/96' xj
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« Reply #5 on: 06/13/09 - 02:11PM »

Oil pressure develops when there is resistence to the flow of oil.Pump problems aside,low oil pressure can be caused by worn main,cam,and rod bearings,worn lifter bores, stuck pressure relief valves(block or pump mounted),clogged pickup screens,loose pickup tubes,or otherwise clogged passages.High oil temp, wrong viscosity,and low oil level can cause the problem as well.Pressure does not equal volume,however,there should always be at least 10 psi for every 1000 rpm.
« Last Edit: 06/13/09 - 02:13PM by Willysman23 » Logged
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