crankcase venting

[hound dog]

A quick look in my gallery shows my engine setup. If you look closely at the passenger side valve cover and the vent cap, you'll see the small nozzle coming out the side near the top. Normally this gets a hose attached and routed back to the carb. base plate, but a friend told me to route it to the headers instead. My question is "is there enough vacuum in the headers at idle or around town speeds to vacuum out the crankcase"? Or is there actually positive pressure in the headers at this point and will it blow exhaust gasses back into the crankcase? Opinions please.
h dog

[SFfiredog]

Hello,
Exhaust scavenging of the crankcase or "pan-evac" has been around for a long time in drag racing circles. Unfortunatley, it is only effective above 5000 rpm and requires a 5/8" to 3/4" hose routed from each valve cover to the header collector. An anti-backfire valve (one way valve) must also be installed in the hose from the header to prevent exhaust gases from being blown back into the crankcase. it is not effective or practical on the street.
HTH
Mike

[hound dog]

f dog,
That's kind of what I was thinking too. My friend is a big drag racer.
h dog

[Mr.Fixit]

Exhaust scavenging only works at high RPM . My favorite way to vent the crankcase is with a 1.5" metal tube, connecting the valve covers, with two standups on it with clamp on breathers on those. The tube is connected to the valve covers via 2" long pieces of rubber hose for connecting the tubes welded to the covers.That sounds confusing, each valvecover has a 2" long metal tube welded to it, these attach to the "bridge" with short sections of rubber hose, the bridge has two stand ups with the breaters on them. It will allow tons of air to escape, and oil can't make it to the breaters and get all over everything. Also, no oil getting sucked into the intake because your shiny aluminum valvecover have crappy baffles.to stop the oil from going into your pcv hose. For the drag cars, I like mechanical vacuum pump sucking on the crankcase.