i'm runnig 10w30. my guess is the oil is too thin for track use and the repated high rpm with oil temps 220-240F are turning the oil into a water-like viscosity. i'm thinking the valve cover gases going to my catch can are just carrying liquid oil into my catch can. i'm relatively certain it's not "blowby" due to the sheer amount of oil. normal driving with occassional wots liiterally puts 1-2 drops of oil in my catch can after weeks of driving, and maybe a few tablespoons of water condensation. this time at the track it was completely different.

next track day i'll probably run 15w50 or so and report back.

Thoughts?

Can't imagine another reason why it would be happening unless you have way too much oil in there!

this time it's different. just getting a lot of oil in the catch can but i'm pretty certain its not an indication of exessive blowby or worn rings

I noticed when I cut open the stock valve cover vent line that comes from the RB25 vertical fitting that there is a little metal puck with a 1/8" hole in the center of it. Do you know if the RB26 had something like that?

ive never had (or looked at) the factory breather lines so i don't know if there is a restrictor in them.

http://www.mines-wave.com/engl...E.htm

I do like to hear more about your oil weight theory/experiement.

I am not a fan of the rear drain mod. Nissan never thought it was an issue hense.. not doing anything to the past 12 years that the gtr was out.

I do instead gasket match the oil return between the block and the head. If you are using a modified gtr oil pan, there's traps in the oil pan with tiny drain holes to drain the oil out, I enlarge them to let more oil drain. I am still working out a oil return baffling on the oil pan, still in planning stages.

Modified by Rare_f8 at 2:27 PM 7/20/2008

If you have excessive blow by hook a hose to one side of the catch can going to the intake hose and another to the head and the suction should draw a lot of the crank pressure out reducing blow by.

1990 240sx (RIP)
1989 240sx (sold)
1996 240sx 408ci V8 (sold)
1972 Datsun 240z LS1-T project (in progress)

not a fan of the rear drain mod myself either... but that's just my opinion.

Quote, originally posted by HxC_Nismo »

+1 where did you buy em from?

rhdjapan

Quote, originally posted by Blown240sx »

Are you blowing by that much before over filling or after? Over filling is going to cause some blow by issues also. If you have excessive blow by hook a hose to one side of the catch can going to the intake hose and another to the head and the suction should draw a lot of the crank pressure out reducing blow by.

it doesn't seem to be affected too much by the overfill. i have my oil usually filled to the first hump on the dipstick. maybe .5 qt over the high mark. on street driving (with occassional WOT runs but not back to back like the track), my catch can BARELY fills. literally 3-5 drops of oil after weeks with about 30 drops of moisture on top. i can see how overfill might affect drainback into the pan because theres more oil normally in the sump maybe partially blocking the gravity returns

i think hooking a hose to create more suction out of the valve cover will make it worse. oil is getting caught between the blowby gas and the valve cover exits. if there is a vacuum it will just suck the oil and blowby gas out faster. if you take a look at the Mine's diagrams, the light blue is the blowby gas sitting behind the yellow oil. Once oil reaches the valve cover exits, it seems the blowby gas is just going to push it out. the idea behind the baffle plates is to keep the oil from getting to the valve cover openings. In theory it seems like a good idea, so i'm giving it a shot

Nice to know Gawd, too bad they dont make one for the 25 cover's.