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420A High oil pressure blowing filters

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jesse12345

Proven Member
455
329
Jul 30, 2014
Down the block, Minnesota
Okay so I just got my engine put in about a week ago and finally wired everything up car started it runs great but my problem is oil pressure cold at idle was 60 to 70 and when I'd Rev it up it go well past 100 and my first oil filter I had was a small 348 the gasket blew out of so I put a 085 on there which is what they take and that sucker blew up like a balloon its now round. I'm at a loss I completely disassembled the motor before I put it in everything was in great shape I got new rings and a new oil pump and that was it it also has a turbo on it now. Nothing smokes or anything so I don't know if it's the pump or what any help would be great thank you. I also posted a pic if anything looks wrong let me know its been a hot minute since this thing has been running.

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I can't see the oil pressure getting high enough to bulge out a filter. There is a pressure relief valve built into the oil pump. It should start opening around 3000 rpms and fully warmed, shouldn't get over 90 psi.
All i can think of is either the relief valve is stuck closed or you have a major blockage in an oil passage.
But i would think you would have already fuct something up if you had a blockage somewhere.

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So do you think I should get a better oil filter or get a new pump? I really don't want to pull the pump but if I have to I will. I haven't ran the car long enough to really warm the oil up, but it settles down to 50 psi running for 5 minutes. It's only when I Rev it up.
 

BLACK'98DSM

do you know why your oil pressure gets that high? are you running really tight clearances, high flow oil pump, or did you shim/change the relief spring or anything like that?
 
I tore the engine down and put new piston rings in the bearings looked extremely well like someone had rebuilt it once already. I got it from a junk yard and they couldn't verify if it was good or not thats why I tore into. Long story short everything was put back exactly how it came out except for the rings because they broke when I took them off hence why new rings were put on. The oil pump was an ebay oil pump so that could possibly explain why its not functioning properly I have no idea but I do have a wix filter on but I will go for the k&n. Do you think I'll have to swap the pump or maybe a better quality filter? All I know is the engine runs great it sounds very healthy.
 
I don't usually advocate throwing parts at a problem without tracking down the culprit first, but if it were my car, I'd get a known good oil pump. The Melling M190 is the model that used to be most popular among 420A owners. It goes for $91 on RockAuto as of 4/2021.
 
He said "well past 100 psi", which makes me wonder if his gauge only reads up to 100 psi.
 
I wouldn't say 101 psi, for instance, is a dangerous pressure, but we don't know how high yours is because your gauge can't read more than 100psi. I would guess that it's much higher if the oil filter is bulging. The oil pump is such a critical component, I just wouldn't trust an eBay part for the job.
 
Exactly why it's going to come off. I have no idea when I bought it, it's been so long the only thing I know is it more than likely came off ebay which was a big mistake on my part. I always thought an oil pump was an oil pump I have learned from my mistakes. Do you think I can remove the oil pump without removing the engine? The 420a is such a pita to put back in.
 
the 420a is one of the easiest engines to pull and put back in.
disconnect everything, drain the coolant, pull the radiator, move the PS pump out of the way, remove the clutch cover and the 2 support brackets, unbolt the flywheel from the flex plate, attach your hoist, remove the bell housing to engine bolts, remove the engine mount, then get a prybar and separate the engine and transmission. Just use the prybar to keep the engine and transmission far enough apart so the flexplate clears the bell housing while the engine is hoisted out.
It drops back in just as easy. you just have to make sure to again use a prybar to get the flexplate to clear

if your technique for breaking the crank pulley bolt loose is bumping the starter, don't forget to do that first.
 
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I use to have a few 4gs. The hardest part removing the 420a to me is the dang transmission diff getting hung up everytime when I try to get it back in. This is my first 420a since high-school, 8 years ago which is why I'm back in one. I haven't put the pulley or anything on yet. I was just curious if pulling the pump was at all an option without pulling the motor for the 4th time. Thanks for all the help guys really appreciate it.
 
you can change it with the motor installed but for me anyways, it easier to do it with the motor pulled


in relation to my previous post,
im pretty sure i supported the transmission and pulled off the crossmember before unbolting the flywheel 'n shit, then reinstalled it. my memory sucks and i've pulled and installed so many different engines sometimes i mix shit up. But for sure you can pull the engine with the tranny in place.



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