Leak Down Test And Forged Pistons And Hard Rings

[The Bogan]

Ive had my motor rebuilt and Im having some oil issues, Ive got forged pistons and "hard" rings, my leak down was at 15%, Ive been told that that is OK by a couple of different shops, Im not making enough blow by to cause alot of positive pressure in the sump but with all oil mods done from the oil surge thread, Oil Control In Rb's For Circuit Drag Or Drift, here> http://www.skylinesaustralia.com/forums/topic/110680-oil-control-in-rbs-for-circuit-drag-or-drift/

Would 15 % be enough to not allow the oil to flow to the sump, Ive got 2 x 1mm restrictors (RB25 hydraulic head on a RB30 block), opened up oil gallery returns, head drains to sump, head vents to catch can with a return to a winged baffled high volume sump.

Im using a TOMEI pump which has had 1 spring removed.

This has been a nightmare for a while as whenever I go to the track it pumps a couple of litres of oil out the catch can breather.

The mechanic is at the stage of doing a seperate feed to the head to try and control it.

Surely its not rocket science, but its causing our brains to seize.

It never happened once with my old stock 200,00 K RB25 motor which was a heavy breather.

This is all warranty work from the shop BTW, which to there credit are doing everything in their power to fix it, engine has been out twice so far and the heads been off three times.

Anyone else using a TOMIE pump and having/had issues ?????

HELP ME.................................

[MrStabby]

The latest issue of HPI has an article that states that the rocker cover baffles are vital, and that a lot of engine builders remove them.... The article is about RB26s but I imagine 25s have similar. So - are the baffles still there?

[rob82]

I'm assuming the leak down was due to ring seal issues? Most engines in good condition should be below 5%. What is your oil relief pressure? And yes STD engines don't have oil control issues - it's because the blow by is minimal, and the STD pump doesn't pump too much oil to the head.

[The Bogan]

Baffles are still in place, I cannot remember oil pressure off hand but Im thinking it was around 90ish psi from memory, it was around 110 psi before the spring come out, at 7200rpm.

Its got better from when it first happened, but from my reckoning it wold take 1 x 1mm restrictor to get the job done and Im not sure that it would feed enough oil to the head when the car is at idle.

Its frustrating because my set up is meant to breath a bit heavier until its up to working temp, it just doesnt get the chance to get hot enough to close down the tolerances, maybe.

I do 2 warm up laps and its fine, then on the 3rd I get right up it and out comes the oil.

LOL, strange my problem may be to much cooling, maybe.

aaaarrrrrgggggggggg.

[r33_racer]

I still reckon that leak down is no good. Usually anything over 10% is heading close to rebuild territory. Does the leak down show any of it coming from valves?

[noone]

mate used an external oil regulator (like a fuel reg) cant find the link i had for it though

though google found this

http://www.xtremerotaries.co/products/oil-system-and-dry-sump-kits/oil-system-components/e531-external-adjustable-oil-regulator

might help lower oil presure issues

cant comment on ya leak down test though sorry

Edited August 29, 2011 by noone