Originally Posted by Airborne350G

Wasn't sure about the crankcase breather so I had to search on it. I found this on the net and it is pretty interesting:

"First off the breather only lets the engine breath one direction, this was fine from Flat Head days to EVO days but the Twin Cam motor is an internal breathing motor. This means the TC breaths from the crank case to the cam chest and then up to the rocker boxes when the piston is on the down stroke, (very little air escapes the engine through the two small holes in the head breather bolts) as the piston goes up the bore the air is pulled out of the top end into the cam chest and through the pinion bearing into the crank case again. During the up stroke of the piston and air traveling into the crank case there is a pull on the oil in the top end that assist in the return of that said oil into the cam chest for removal. If you install the S&S breather it only allows the air to pass through the bearing from the crank case to the cam chest one way....now as the piston goes up the bore the breather stops the air from cycling back through assisting in oil drain from the top and causing a vacuum in the crank case which you DON'T need with this Twin Cam breathing design. Now the oil has to return by gravity alone which slows the return process so oil can be actually filling the rocker boxes. All the oil is directed into the cam chest now in the TC not the Crank case. EVO's and earlier Harley's the oil from the top end was directed into the crank case and their breathers where designed to make that vacuum in the crank case to assist in oil return from the top end. (there are other reasons for crank case vacuum too but thats another topic)
Bottom line in my opinion the S&S breather is just another way to get you to shoot the lock off your wallet....it's not needed and it's a waist of time and money. It doesn't help in scavenging oil out of the cam chest back to the oil tank and that is the ONLY way to prevent oil carry over....get the oil back to the tank."

Originally Posted by SURFOR Chop

* * * below is a copy of my post in Dyna section ... thought I'd post over here for possible additional input * * *

I ordered my cam gasket kit ... also ordered a S&S crankcase breather valve that goes outboard (I believe) of the oil pump on the end of the crankshaft ... supposed to significantly reduce the crankcase pressure that forces oil into the head breathers ...

Got the following feedback from forum member Airborne350G:




Guess I should've spent the money on the special cam install tools instead ...

* * *

For a while, I was having a little issue with oil blow by ... getting oil coming out the A/C and drips on the top of the cam chest ... not too much, but noticeably more than some other bikes ....

Must have been hornswagled by the fancy graph on the S&S website comparing crankcase pressure with and without ... I'll admit I'm a bit skeptical as to how much oil is actually going to accumulate in the rocker boxes according to the warning above ....

Guess I'll find out ...

Anyone have one of these already installed who can opine about whether it helps or hinders performance ...?

Thanks for the input ....

R/
'Chop

Originally Posted by Hillsidecycle.com

It nether helps, nor hinders.
If you have oil in your air cleaner on occasion, drill the oil drain in your rocker arm support plates, with a .125" drill, and try running the oil bag about 1/2 qt low.
That should dry things up, and is basically free, expect for a little time.
Scott

Originally Posted by jcb1975@yahoo.com

No picture, but the hole is in the rocker arm plate, underneath the umbrella valves, that little sponge with the rubber diaphram. It is inside of a little case held to the rocker plate with two bolts. I recently did cams, tensioners and bearings and while I was in there I went ahead with the H/D breather upgrade and drilled the holes to .125 . Made no difference at all. Still get the smell when decel in gear, still get oil out of the A/C. Have only been adding 3 quarts of oil at changes, making the oil barely on the safe zone of dipstick when warm. I think a H/D has to leak a little oil from somewhere or they just aren't happy.