Nicks2319 said:

So is anyone offering this service for $$$ yet? I'm about to receive my 90 style housing, and I need it ported but do not have the tools or know how.

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I don't think anyone would want to do this work for someone they didn't know at any price knowing the risks/liability.

If you currently have a high oil pressure problem (e.g. goes over 100psi) here's a quick FAQ on how I did mine:**

1.) Remove that large shiney (if new) brass bolt which holds the relief spring and piston into place.
2.) With a small flat file (cost you a buck or so at any hardware store) carefully profile the top/sides of the OEM teardrop shape (e.g. "U" part furthest from the bolt you removed) so that it looks like "|_|"). There is no exact formula for how much to cut away as oil pressures vary, just be careful not to cut too much from the top that you expose the top of the piston when it's at rest.
3.) Finish off with some 220+grit sandpaper to smooth/debut the edges of the outlet port.
4.) Thoroughly clean the work area with solvant to get rid of any/all AL particles.
5.) Put some fresh oil on the piston and reinstall.

It should take you no more than 10mins start to finish.

**Liability Notice: Note this is what I did and it worked for me. Do at your own risk

If I am right, I assume that this relief valve works like a waastegate. So in theory the larger the hole on the piston the more efficiently it releases the pressure. If your not sure what I'm talking about I provided a picture of the hole I am assuming would work best to port.

I've ported my relief hole pretty good and I've pushed out 2 oil pump seals so far within 2000km. I've also blown the seals on my turbo shortly after I built my g4cs. My next turbo was smoking badly from the getgo until I fed it from the head and went from a -4 to a -3 line. The pressure on the stock gauge doesn't show anything abnormal....I'm about to try the N/T piston and spring and see where that gets me and also installing a real gauge.

After porting that hole the oil pressure reduced from +6 bar (+87 psi) to 5 bar (73 psi).

babyviper said:

If I am right, I assume that this relief valve works like a waastegate. So in theory the larger the hole on the piston the more efficiently it releases the pressure. If your not sure what I'm talking about I provided a picture of the hole I am assuming would work best to port

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The piston hole is not what needs to be ported, its the aluminum filter housing bypass hole itself. A better port job would be to port more of a straight edge (as shown by the red line)



Note, pushing oil past the turbo oil rings is not always due to high oil pressure. Remember that what goes into the turbo's oil jacket must come out, so if the return line is undersized or otherwise restrictive (excess crankcase pressure, kinks, crap in the line) even normal oil pressure could push oil past the oil rings

Well I installed a gauge and I'm showing 100psi by 3000rpm then it suddenly drops to 80psi but resumes pegging the gauge by 4000rpms. I take it the relief opens but can't flow enough.

I changed oil pumps from a newer Topline to an originial '90 and there's no difference.

I changed the spring/piston to a non turbo, no difference (btw, they are exactly the same dimensions, I measured with a digital caliper)

I am really baffled here as i ported the relief bigtime! I have a g4cs block, no ballance shafts, no oil squirters of course.

Here's a pic of my relief hole, could I have ported too much which could interfere with the proper operation of the piston?

Yours is ported about the same amount as mines. maybe a little more, but doesnt appear you ported above the piston which is good... I dont think you can port it too much as long as none of the top of the piston is exposed, you dont want to exceed that. Basically you just want it to release more oil pressure as its opening with having a larger hole, but you dont want it to be releasing pressure due to porting it above the piston before it even has enough spring pressure to start opening. That wouldnt be good for low rpms and idle id say. They say every 1k rpms should bring close to 10psi of oil pressure, so theoretically if you see anywhere from 10-20 psi at idle by 8k you should have 90-100 psi. So id like to assume you should never exceed 100psi of oil pressure unless revving beyong 8k. But that would probably be on an improperly venting unported relief valve were it wasnt relieving any additional pressure after its full opening point which i recall being like 85psi correct me if im wrong.

(Side note for those whove never ported= Porting the relief valve is very easy to do with a hand dremel ive done it twice, most ppl just dont like the work involved in taking it off... Having a real oil pressure gauge should come first before guessing that your oil pressure is too high though... )

I dont have oil pressure issues so im running 15w50 full synethetic Mobil 1 ( From walmart.)
Id like to run 20w50 on this old motor though especially since I dont have an oil cooler and would like to autox
and I believe the closer the two numbers in the oil wt the less additives..

Btw, GSX Dan what kind of oil are you running?
Also I know a lot with the clearances of your bearings and how tight your motor is could dictate your oil pressure, but i dont see why you pressure is that high with a relief valve ported such as yours. Are you positive the piston is sliding back and forth correctly and not getting stuck on any sharp edges?

Black_Bullet, I am running 10w30.

I removed the filter housing yet again and I was about to port out another one when I realized that I couldn't do it any differently...except smaller. So i decided to cut the spring. This actually worked! I cut about 2 coils and it brought my oil pressure to about 20psi at 1500rpm warm, and it climbs nicely about 10psi for every 1000rpm. I would only recommend this in conjuction with the porting and if the porting alone didn't help. The best part is the housing doesn't need to come off to get access to the spring, so cut it in small amounts.

I have a spare 2G oil filter housing laying around the garage. I'm going to research how to test the spring pressure and I'll try to get some numbers. I'm not pushing myself to get it done, however I'll piddle with it a bit.

GSX_Dan said:

Black_Bullet, I am running 10w30.

I removed the filter housing yet again and I was about to port out another one when I realized that I couldn't do it any differently...except smaller. So i decided to cut the spring. This actually worked! I cut about 2 coils and it brought my oil pressure to about 20psi at 1500rpm warm, and it climbs nicely about 10psi for every 1000rpm. I would only recommend this in conjuction with the porting and if the porting alone didn't help. The best part is the housing doesn't need to come off to get access to the spring, so cut it in small amounts.

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Thats good to hear it worked for you...
I wouldnt recommend cutting this spring without a oil press gauge though.
I imagen that cutting it too much would cause you to bleed off too much psi at idle.
GSX dan I still personally think that your piston/spring was getting stuck or hung up
because all cutting the spring did was cause it to start releasing pressure a little sooner but
at max spring pressure were its fully opened it shouldnt be any different than it was before.

What problems can come come from high oil pressure beside blowing seals and such. If you are running high oil pressure and rev your engine high can it have affects on the proformance of the engine.

herblove said:

What problems can come come from high oil pressure beside blowing seals and such. If you are running high oil pressure and rev your engine high can it have affects on the proformance of the engine.

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High oil pressure in the head can cause HLAs not to fully collapse leading to valve float.

Another potential problem could be over oiling a journal bearing turbo causing slower spool and eventually blowing turbo seals and high oil pressure will destroy a Ball Bearing Turbo CHRA which is very costly to replace because you can't rebuild them.

This is the correct way to port an oil pressure relief passage.
You want to enlarge the passage as much as possible towards the top of the piston so the piston doesn't have to travel very far down on the spring to relieve the pressure.
I opened up my oil filter bracket on my 97 GSX and my friends 92 GSX, and his pressure doesn't get above 80psi at WOT.
He ported his oil pressure relief passage once, and he was still getting oil pressure above 100psi at WOT.
He pulled his bracket off and I ported it for him just like the pic below, and now he is all good with nothing above 80psi.
Just make sure you don't port the passage too far up so the piston doesn't seal at lower pressures.
The factory set-up with balance shafts is set to open at 78psi, so i think we hit the nail on the head with this one.
He has gauges, and we were very pleased with the results.

DSM90AWD said:

High oil pressure in the head can cause HLAs not to fully collapse leading to valve float.

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Thanks that is the answer I was looking for. I am having a problem getting my car to rev pass 6300 rpms and it acting as if the spring are to weak and are causing vavle float.

hey guys... think about this for a min.. what does the NT oilpump-setup do with all that extra pressure? ...figure that out and apply the results to the turbo block. you wont have to port anymore.

i kept my ported housing for one reason alone... i like the factory oil cooler w/ its housing (opposed to the middle-man unit found on ebay). i haven't ported another housing since i found the difference.

The way I see it if you're building ~80psi of oil pressure by 3000-3500rpm and then the relief starts to open you still got a problem that's why I'm extremely happy with clipping the spring as well. Now I have 25psi at idle instead of over 40, and as the revs climb so does the oil pressure 10psi for about every 1000rpm. This is very unlike the stock setup where it pegs at 80psi half way through the RPM range then the relief opens and holds that pressure but I will be inspecting my main/rod bearings this winter as they are fresh and see how they survived so far...although i'm expecting them to be washed out from when I was running tremendous oil pressure pre-spring clipping for a good 1000miles...I blew through some perfectly fine journal turbo seals because of it and the motor revs much easier seems like...I never had a noticeable issue with valve float due to non collapsing lifters even on my FP 3x cams reving to 8K...also the non turbo internals even if different(I honestly didn't see/experience any difference and the piston/spring had identical dimentions) aren't setup to deal with the extra pressure from blocked ballance shafts. How sure are we the non-turbo motor simply doesn't run higher oil pressure? An accurate test would be to take a stock turbo and non turbo motor and record the oil pressure readings at specific RPMs and under WOT. I would do it but I don't know anyone with a non-turbo willing to let me use their car as a guinee pig

I've read all 4 pages of this thread so far and I think I get the idea. Could someone post a clear (as clear as there camera will get) pic of a bone stock piece and after the porting is done? I just want to make sure I know what I'm doing before I start.

Great info in this thread! Ive been looking for a cure for my 100 + psi oil pressure after my build.

wow you really have to look to see whats going on... I didn't realize that you really need to take away so little material. Thanks mav....

The black portion in the picture is how you want to port your oil relief hole.
You want the leading edge of the pistons larger diameter to just seal the flat portion you create in the oil relief hole shown as black in the pic.
You want to create a wide and flat opening nearest the source of pressure.
That way the piston doesn't have to compress the spring 1/2" or so to relieve the oil pressure.
It's all about flowing volume of oil, not oil pressure.
The larger you make the hole really doesn't help, it's at the top that you want to open up,
make it flat and flow a rectangular volume of oil instead of a half moon volume of oil.... get it.
I've done three oil filter brackets using this same method, and have had excellent results.
The best was with a 92 6-bolt previously pegged his oil pressure gauge to 100+ psi at 4k rpm, now at 7k he only sees 90psi...

So have we figured out yet if the NT air cooled housing has a different spring than the turbo air cooled housing?

hey just seeing if any of u guys have any more pics or good results with the way ## porting the the relief...

I have done it long time back ... after that the oil pressure is within limits.