I have a 1990 240SX wit the KA24E engine. As I've mentioned in a previous post (zerothread?id=132756), my oil pressure has been low after rebuilding the engine. Since all my bearing clearances were well within the stock spec (according to the FSM) and switching to 20W50 had very little effect, as well as shimming the oil pump pressure valve, I was wondering if the low oil pressure could be caused by the pressure relief valve in the block where the filter is.

Here is how the pressure acts: At cold startup it'll go up to 30 and then quickly drop to 10 or less psi at idle. My head clatters pretty badly, although it seems like it's only one rocker arm that's doing it. As I rev the engine, the pressure will go to around 40psi at 3k rpm, and stay there no matter how high I rev it after that (I haven't gone over 4500 to not damage the engine). Since I've replaced the oil pump yesterday and the pressure acts the same, I know it's not the pump or its valve. The only other thing I can think of except for something majorly being wrong with my rebuild, is that little spring driven ball (FSM calls is Oil Pressure Relief Valve)in the oil filter location. But I also know it doesn't take much force to push it in, so how could it possibly be responsible for my major oil problems?

Please give any advice you can, I'm really bummed out about my lack of success with this rebuild. I hate hearing my rocker arms clatter like on some beat up old truck and I don't drive the car now because I don't want more damage to occur.

Also, I was wondering if the addition of the turbo oil feed line could be responsible for such an unusual oil pressure drop? I do have a restrictor on the feed line, installed at the turbo end, so that the turbo seal doesn't get too much presure, but who knows? Then again, lots of people have turboed their KAs and don't seem to be having any problems with oil pressure.

sil80
Modified by sil80drifter at 3:30 PM 9/6/2005

bump.i'm glad someone is trying to help me out.

sil80

There is a gold restrictor at the top of the block between the block and head. Is that still there and the same size it was before you built the engine? That restrictor is to help boost oil pressure. If it is missing you oil pressure will drop to half which is where you are.

I haven't taken this restrictor out when I was rebuilding, so it should be the same as before the rebuild. I hear that little restrictor could have a gasket around it, in which case when not replaced it could lead to pressure problems?

What I did over the past two days is drop the oil pan and replace the oil pickup gasket between the pickup and the block. When I was assembling the engine, I didn't have a rubber o-ring, so I made one out of silicone sealant and waited for it to harden before I put the pickup back on. When I took it off just now, the sealant was kind of everywhere and no longer in the o-ring form (possible leak?). I replaced it (after a thorough cleaning) with a real rubber o-ring (NAPA). Hopefuly this was the fix, I'll start up the car tomorrow (after the silicone on the oil pan cures) and see if this fixes the problem.

If it doesn't, and the only thing I haven't checked is that little restrictor, I'll be really mad because I would hate to pull the head again after having it off last week and not have done the restrictor check. I hope it's not the restrictor. But I'll replace it it if it is.

sil80

Ok, the o-ring had no effect on the oil pressure. It's still down at like 30psi at 3k rmp, and revving the engine has very little "visible" effect unlike before. Since the restrictor is the only other thing left I haven't checked/replaced, I assume it's what is causing this low pressure problem.

NISTECH, that retrictor you were talking about... Can it be repaire/purchased when I take mine out (whenever I do that)? If so, where/how?

Just to make sure we are on the same page you are talking about the thingy that is circled red in the pic, not blue, right? Cuz the blue thingy is just... nothing really, but it looks goldish. Also, I tried to take that red circled thingy out on another block I have lying around and didn't get anywhere.

sil80
Modified by sil80drifter at 8:49 PM 9/7/2005

The thing circled in red is what I am refferring to. You sure it was there when you assembled the engine? If so thats not your problem. The oring you mentioned was a very likely culprit. Are you leaking any oil at this point?

As I've said, I replaced the o-ring without any noticeable results. Since it looks as if the red circled thingy is part of the block itself (I could not even make it budge on my spare one), could it have been damage when I was cleaning up the rests of old headgasket from my rebuilt block, and kind of "shaved" that red circled restrictor?Yes it was there when I assembled the block, and it was there again when I took the head off to fix a bent valve last week.

I am not losing/leaking any oil (some is coming ou of the valve cover gasket, but that's minor and I'm getting a new valve cover gasket).

So now that I've replaced the o-ring, I've pretty much exhausted all of my options, correct?

I've replaced the oil pump, back and forth from the 280Z one to the stock one (no effect), I've shimmed one of the pumps (5psi increase), I've switched to 20W50 oil (10psi increase), and I've done the o-ring (no difference). My idle pressure is around 10, but it doesn't move when I press the gas, until I am at about 3k rpm, at which point it goes up to 40psi.

My rocker arms clatter and my oil gets dirty really quick because there is a lot of friction on the pisotn rings which are nto being lubricated properly.

I don't know what else to do.

UPDATE: I revved to red line, and at 6500rpm the pressure is 70psi. Is this WAY too low?

Also, that little restrictor you were talkign about. I looked at my head and the place which corresponds to the location of the restrictor is not (as I used to think) an oil feed gallery, but just a head bolt, with a cutout in the shape of the same one in the headgasket. So... Do you think maybe oil is getting past my headbolt and that's why I have low oil pressure? m I mean what is the exact purpose of that restrictor? The oil doesn't go anywhere after it comes out of (IF it comes out of) there... Does it?

sil80
Modified by sil80drifter at 5:43 PM 9/8/2005

update 2:

oil pressure now at 50psi at 3k rpm, and around 80 at 6500.

This is good enough for me, I'm running 3 quarts of 20W50 and one quart of that lucas oil enhancer stuff (kinda thick and goey but works well I hear).

I have had enough with this, and since anything else I could do to try to fix this problem would be a rebuild, I may as well have fun with the car before I do it.

Compression is at 190 190 200 200 (my compression gauge sucked I think it's really 200 across the board), which means the car broke in well (inspite of my crappy oil issues), so I'm just gonna start boosting ehr at 6psi (and max out the 270s with the SAFC), and then tomorrow put in the 460s and take them for all they are worth. Around 250rwhp I hope.

We'll see how good I am with SAFC tuning I guess.

Thanks for all the help and advice, I'll update the KA-T section when I get some results.

sil80

sidenote:

don't use that lucas additive crap; just a good quality oil...

http://www.bobistheoilguy.com/...s.htm

hopefully, those chunks of sealant didn't restrict an oil passage...

HOLY CRAP! This is aweful. What I'm wondering right now though, is how come he didn't use THE SAME oil on both sides, so we could see the results with SAME oil, one with additives and one without.

Still this kind of scared me to death and hence I'll be draining my oil to check on it in the next few days. Thanks ricebike,

sil80

sil,

yup, ever since Fred, the oilguru of NICO, is getting busy w/ his real job, i found that guy to be just as serious when it comes to lubrication/filtration/etc...