Hot Street PCV from crankcase?

I think this is what your looking for

The purpose of the vent is to VENT the crankcase to AVOID a vacuum in the crankcase. The reason that some folks hook the vent to the valve cover is that some racing associations very likely want any outlet on a bike that is capable of slopping oil on a track to provide a catch system. You might want to check the vintage racing associations for their rules. It seems kind of non-useful to do this on a street bike. The main thing that can happen is to fry a ring and have a ton of blow-by which would foul up a track and stop a race. This seldom happens on the street.

I think that the idea of venting the crankcase to the valve cover is actually to the smog covers. they create vaccum(like going to the header) since their purpose is to suck air into the exhaust. just venting to the cam cover doesnt get the air out of the engine. you could just stick a small K&N on the crankcase vent if you want to make it easy and look nice. going to the header definatly screams drag bike though(most drag bikes block off the smog stuff anyway), looks like 95% of the cars at the local track, they all vent the valve covers to the headers this way

there are atmospheric pressure differences both on top of and below the pistons as they travel up and down the cylinders.

sealing the crankcase by a hose to the valve cover will trap the positive crankcase pressure and force the oil to go where you do not want it to go-- like outside the engine through the weakest point- or points.

#1 venting the case and cam cover is necessary
#2 having a neutral pressure in the case is necessary

running it to a filter is good (street)

to a catch can is good to contain fluids and is often required by track officials

to the exaust takes metal work and the performance increase is NOT enough to warrant the effort

I say just make it look good

Thanks guys lots of good info. Thanks for the pictures. I knew I wasn't somkin' bananas :laugh:

The purpose of the vent is to VENT the crankcase to AVOID a vacuum in the crankcase.

I was just reading a thread on an engineering forum where I'm a member. Especially in an engine setup like a 4 cylinder where there is always a piston going up for another going down, what you want is crankcase vacuum. Well, not for emissions, but...
The lower you get the preassure in the crankcase, the less turbulence resistance on the rotating parts. According to one source, "Smokey" Yunick concluded that as little as 5 milliPascals of vacuum (less than 1 PSI, or less than 2") gave his stock car motors 15 extra HP, or about 2 percent. Not much for street use, but every little bit helps when racing. Some clubman racers in Merrie Olde Englande claim the same for their bike motors. Don't know about that, but I'd take Smokey's word for it.
Furthermore, a slight vacuum in the crankcase makes oil rings more efficient, leading to less carbon fouling of the combustion chamber.
Now, the cool thing is, with the Kaw motors with the emissions stuff on the heads, fitting a pcv valve between the crankcase breather above the transmission and the ports on the valve covers, you get good crankcase ventilation AND it looks like you have your emissions stuff hooked up!!!!:woohoo:

Post edited by: pstrbrc, at: 2007/01/31 11:46

Post edited by: pstrbrc, at: 2007/01/31 15:05

My Buddy uses a Ford Air Pump like for emissions , to get a vaccumn in the crakcase of his 900 hp Pontiac Drag car .. He agrees with the above post as far as HP gains

Thanks for everything. I learned a lot. I never knew about using vacuum pumps but it's given me some work to think about.

I'll keep y'all posted on where we go with this!

What about one-way check valves? Would a one-way letting air in, and then a one-way letting air out do anything? Just thowing this aganst the wall and seeing if it sticks.

Of course it would.

A PCV valve is a type of check valve. Usually they have no force to overcome in the positive direction and close immediately in the negative direction.

Other types of check valves require a certain flow in each direction to hold and others are always off in the negative direction. Many types and many combinations.

That's why I asked the question in the first place so that I don't have to go through all the guinea pig tests to find out what works. :silly:

Again thanks for all the 'free' knowledge I 'owe you guy's a beer':laugh:

If you drop in us Canadians have lots of cold ones eh!:laugh:

Here's the Gast pump: www.fastbygast.com/Catagories/Products/description/vacuum.asp
This is "race only stuff"
The to the collector method is prodably worth .01-.02 in the 1/4 maybe a mph or so. You'd never notice it on the street but when your trying to set records that last hundreth can be critical.