Ok, I took apart my old oil pump, and its only got a few parts inside of it. Instead of getting a whole new pump, i can rebuild it with new rotors and new pressure relief vave and spring for about 45 bucks. I cleaned it all up, and checked all the clearances from the overhaul manual, and everything is perfeclty in spec, just a few small score marks on the rotors and pressure relief valve. So i'll just get the new parts, and reuse my pump housing. I have heard we can do somethng to the pump to get more pressure/flow much like the Melling units, as i believe the Melling is just that, a worked over stock pump. So does anyone have any insight to this -> Rebuilding the stock pump,and getting more out of it. Thanks for any info.

I wish I had hard fact for you here, as far as what exactly to do.

But, The spring that regulates pressure "should" be able to be changed or shimer with a washer, to increase pressure. A stiffer spring or washer should allow for a raise in pressure. I wish I know exactly what ratings spring or what size washer would do the trick for it. I would love to get 5 to 10psi more out of my oil pump.

The muscle car guys have been swapping out springs to raise pressure for a long time. There has to be a good swap for us to get that extra pressure. Would be a fantastic addition if you are turbo, have big cams, added an oil cooler, etc. Anything that promotes slightly lower pressure.

I don't see a problem with the internals of the pump on handling a handling the 5 or 10psi increase. Now lets figure out how to achieve it.



15.9 @ 86.7mph
97 Eclipse RS

Injen CAI, 55mm TB, P&P Intake, Crower Stage 2 Cams, Hooker Header, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

Trial and error i guess.. measure a washer thickness, shim it, see how much it increases the pressure. Then we can start to guess a little, and say x washer thickness provides y more oil pressure over stock.

Just keep in mind, too much oil pressure is bad too, and 50psi is quite a lot.

I found a Mopar Performance oil pressure sprnig kit for the old 2.2/2.5L motors. Now the oil pump on that is not anythign like ours, it's balanceing shaft/distibutor gear driven... but who knows about the springs.

If you can get me some dimentions on our stock spring I might be able to compare them. I think I have a stock oil pump off an old 2.5L chrysler sitting in my garage, if I do I can pull it and look at the spring.

If not... I like Dino's idea.



15.9 @ 86.7mph
97 Eclipse RS

Injen CAI, 55mm TB, P&P Intake, Crower Stage 2 Cams, Hooker Header, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

The washers your are talking about??? Is it the one that is on the pressure relief vlave plug? The stock spring, according to the service manual, is supposed to be 2.39 in free length. It should test between 80 and 84N when compressed to 1.60 in. I would assume that making the spring have a stiffer tension, will help build up more pressure, so the relief vavle doenst let oil be bleed off as much/quickly?? I guess this brings me to my next question. Do we really need to upgrade the oil pump? I have always thought it was more than sufficient. Here are some pics.





The spring is about 7/16" wide.

The rule of thumb on v8's is 10 lbs for every 1000 rpm. well thats what we used on our raceboat motors. 502ci stroked to 572ci. I dont know if it is the same for us but seems like it wuld make sense.

i am getting about 62 psi at idle and a little over 100 psi at WOT. is that what its supposed to be? how much pressure are you hoping to get by rebuilding the pump?

Hehe, i dont really know. My basis for rebuilding the pump is simple: save money. There just is no reason to buy a whole new pump, if it only contains 2 inside moving rotors, and plunger, and spring, all which can be bought new for 45-50 bucks,instead of paying the dealer 120 bucks for a whole new pump, or 90 bucks for a Melling pump. If anyone with a Melling oil pump feels adventurous, take out the spring and relief valve from your oil pump so we can compare the differences. Hell, if its just a different spring or whatever, then we can have a Melling duplicate pump for cheap...As far as oil pressures, i never had an oil pressure gauge in the car, so not too sure what stock pressures are supposed to be (or were for that matter). I'd REALLY like to see the difference between the stock and Melling pumps..

62 psi at idle, cold right? When warm what do you get? Should be around 20-25psi for stock pump.

That one won't work 420A spring has a free legnth of 2.39" the old 2.5L has a free length of 1.95"

Looks like we are left to shimming... you want to experiment?



15.9 @ 86.7mph
97 Eclipse RS

Injen CAI, 55mm TB, P&P Intake, Crower Stage 2 Cams, Hooker Header, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

Hehe, i'll experiment if reaching the relief spring is somewhat easy to get at. With the block apart, and no timing belt stuff,ect, its hard to tell how easy or hard it will be to acces the spring. I know it will be very close to the crank pulley and the timing belt componets. If i have to take any of that off to reach the spring, then that may really suck to experiment with. But if its easy to get at it, maybe some one can take their Melling oil pump spring out to see what the diff is? And when you talk about shimming, you mean putting more washers on the plug that retains the spring/valve?

I get about 50psi cold, and 15-20psi hot, both at idle. Seems low, but it's likely due to my plumbing setup - i get the pressure signal off the feed line to my turbo.

Yeah 15 does seem low, I'd worry if it drops below that.

The Melling is a stock replacement as far as I know, so there should be no difference. I thought the Melling put out stock pressure.

Yes a washer on the back side of the spring to compress it slightly. Wait... did you say you had an oil pressure gauge or no? If not I have a spare one(half sweep, nothign special, but it would work for experimentation.



15.9 @ 86.7mph
97 Eclipse RS

Injen CAI, 55mm TB, P&P Intake, Crower Stage 2 Cams, Hooker Header, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

No, no oil pressure gauge(i'm running out of places to put gauges haha), but yeah if ya want i'll take you up on the offer. I'm not the most educated when it comes to proper oil pressures. I guess to make some sense, what would be the "ideal" oil pressures to run, hot, with low and high rpm's, running a turbo setup? Also, running too much oil pressure is bad? So what is the happy medium? I always thought the Melling was an upgraded oil pump? It would be great to find out how to give our stock pumps more performance for cheap if all it involves is adding a washer or two :)

I would like to see 30 to 35psi at idle, and 70 to 75psi WOT



15.9 @ 86.7mph
97 Eclipse RS

Injen CAI, 55mm TB, P&P Intake, Crower Stage 2 Cams, Hooker Header, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

I don't see increasing oil pressures over stock to our advantage. Why do you think it's inadequate to begin with? It is a good idea tho' to be able to just replace a few cheap pieces in our stock units instead of buying a new pump. any part numbers off the top of your head?

>I don't see increasing oil pressures over stock to our
>advantage. Why do you think it's inadequate to begin with?
>It is a good idea tho' to be able to just replace a few cheap
>pieces in our stock units instead of buying a new pump. any
>part numbers off the top of your head?

Part #'s for the replacement internal parts for the pump?? Not yet, i'm still waiting for the parts to come in at the dealership. When i get em, i'll have all the part#'s on my invoice. I'll be sure to post them in a few days.

Add an oil cooler/remote filter kit, add a turbo and lots of plumbing, add cam and get more abuse to lifters and rockers, crank up the heat the engine turns oil raising oil temps... on a stock motor, no not a big deal, but getting modded I think it could bennefit



15.9 @ 86.7mph
97 Eclipse RS

Injen CAI, 55mm TB, P&P Intake, Crower Stage 2 Cams, Hooker Header, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

Ok here are the part #'s for rebuilding the oil pump:

Rotor package # 4761538 List price 18.20
Rotor cover # 4556669 List price 30.60
Relief plunger# 2843208 List price 5.00
Relief spring # 1737744 List price 1.85

Total cost at wholesale prices was 41.74

my oil pressure has never gotten lower than 55psi unless i the cars off.

And you are using a stock pump? Very unusual...



15.9 @ 86.7mph
97 Eclipse RS

Injen CAI, 55mm TB, P&P Intake, Crower Stage 2 Cams, Hooker Header, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC