sevenracer

I run a 12A in the SCCA IT7 class.



My motor is running strong, but it has one problem. It is blowing oil out of the vent tube (stock location on the oil filler neck) into a required catch can. I had to switch to a 2 qt can to hold the roughly 1.5 qts spit out during a 25 minute race. It only occurs on track, so I think it happens during sustained high rpm or high g forces.



I believe that the issue is blow by past my side seals, so I will need to do a rebuild in the (relatively) near future. Due to my schedule, I am trying to get in a few more races before I tear the engine down. I'm concerned about running low on oil during the race.





What I'd like to do is put a drain line on the catch can to a fitting on the oil pan.



My questions are:

1. Is the oil pan reservoir pressurized? Do I need to worry about the oil not draining into the oil pan due to this? I think the answer is no, just want to make sure.

2. Any other potential problems with doing this?



Thanks,

Neil

j9fd3s

nope it should work to do that, maybe something simpler though, like having the catch can higher than the nipple?

Lynn E. Hanover

Lynn E. Hanover

True, the oil pan is pressurized, by the blowby gasses the breather is supposed to vent to the catch can.



The stock vent is undersized, even for a fresh engine, but stock the intake manifolds gets the breathing gas in a vacuum, so nobody notices until until we race the car and all of the emissions stuf goes into the trash and a catch can is hung in the car. Now the little pipe on the filler neck becomes very small and any wear on the corner or side seals gives you more flow out of the breather, and the velocity of the escaping gas is high enough to carry away oil that before had fallen back into the engine.



So, if the rules allow, remove the filler neck and take a scrap of 1/2" electrical conduit Remove the stock breather tube and die grind a hole that allows the 1/2 tube to be installed at a steep angle so one end is just below the removable filler cover. If you filler neck is metal, braze or epoxy the tube in place. If plastic epoxy it in place. Use a length of heater hose for your breather line.



If it is still overboarding too much oil, remove the "O" ring from the plastic cover and put it back on. Slip a few ends off of soft cotton socks over the end of the filler. Tye wrap the socks in place. Do one hard lap and check the socks. If oil is not running everywhere, run it that way. I assume you are running a baffle between the pan and the engine, which helps this problem quite a bit. I will draw you one if you need it. The other fix that may help is that you never run a multigrade oil in a rotary.



The oil cooling of the rotors foams the **** out of the oil, and the plastic in multi grades make that problem dreadful. Use a straight weight dino racing oil if you still run the OMP. and a 40 Wt. synthetic racing oil if premixing fuel. Premix a 2 cycle oil at 3/4 to 1 ounce per gallon.



Lynn E. Hanover

Lynn E. Hanover

I forgot to mention that, if you want to drain the catch can into the sump, as all airplanes do, you must keep the end of the drain pipe as deep below the oil level as possible. So that the sump pressure cannot lift the oil column high enough to dump more oil, This system works well also. Of course the bottom of the catch can must be as high in the car as you canr get it.



Lynn E. Hanover

Chris Taylor

You can run a quality synthetic even if you're injecting oil. The reason against synthetic use was some synthetic oils didn't burn clean in the 80's, now they're (mostly) all quality enough there's no issue.



I run 50w Mobil1 in everything; 30w will work, but I get too much oil smoke out the exhaust with the lighter oil.

sevenracer

Wow, lots of good info.



Good point about raising the catch can, I had dismissed this earlier b/c the best place to put it was on the pass side, and I was concerned about starting a fire if oil got onto the header. My vent tube was at the bottom of the can and oil was bubbling out into the engine bay. Shorter tube and bigger can solved that.



What's the best way to remove the filler neck? Seems like I tried to remove one once when cleaning a center iron, and I didn't get it to budge. I'm not sure if it's legal for the class, but I doubt I would get protested or DQ'ed for opening up the vent.



I am running a baffle plate and 10W40 Castrol, and I still use the OMP I can make the switch to straight wt. It's funny, I ran 3 other engines with no baffle and never saw this issue.



An off topic question - I also run premix, 1oz per gallon. Is there a downside to this - ie reduced power, fouled plugs etc? I do it just as insurance, in case the OMP doesn't do it's job.



Thanks!

Neil

Chris Taylor

Whack it with a rubber mallet. It's just pressed in. Hit it from the side (try not to hit the plastic cap) a couple times each way and it'll work its way loose. When you're ready to put it back in, couple whacks on the mouth of it and its back in place. I usually put a little high-temp RTV at the very edge... just enough that it'll help seal, not so much it comes spilling out the top.

j9fd3s

how about just putting the bigger tube INTO the oil cap? be easy, and its higher up...

Lynn E. Hanover

That would work just fine. A big bulkhead 90 in AN spec.



Lynn E. Hanover