At a loss

Dealwitit01

Full member
Points
31
Location
New Orleans,Louisiana- now in SoCal
Car
2000 Wrangler Sport
Need help, had a 4.0 inline 6 put a 4.7 stroker inline 6 my issue is when i have the rpm's up i have good oil pressure around 60 but when i take my foot of the excelerator it goes to about 10 or 0 it's a millings oil pump and never had any issues with them in the past i don't know if it's the cam or if the crankshaft slid forward or moved in anyway these long blocks I've heard has this problem so I'm told just wanted to get some advice before i yank it out again
 
That’s not an engine I’ve had any experience with personally although I did own a Jeep Cherokee Sport with the 4.0 litre in-line. It must be an interesting one, giving you the same cubic capacity as the early V8 Grand Cherokee engine but keeping the in-line formation.

If I understand your post correctly your oil pressure is OK while cruising but drops pressure immediately if you lift your foot. Doesn’t make sense, the only thing that would change might be the crankshaft thrust bearings or rather the position of the crankshaft relative to the thrust bearings. With accelerator pedal down the crankshaft is pushed forward by torque converter reaction but when you lift your foot the pressure is released.

Did you build the bottom end yourself? How sure are you that the crankshaft thrust bearings are installed correctly? Thrust bearings are generally located by a couple of tabs and if they’re not fitted correctly they can start to spin and then they don’t last long. If the thrust bearings fall out of position that would lead to a noticeable loss of oil pressure but not as dramatic as you say.
 
Obvious things to check.
Oil filter blocked or clogged
Oil pump could be worn out have a poor seal so loses pressure.
 
I agree with Waynee! I guess its some sort of blockage. Would love to hear what exactly you did to get it fixed?
Though its an old post but the issue seems relevant to me so i would like to know the fix for it.
 
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