p c v valve?

[bcclew]

used to have crusaders now i have 5.7 chev long blocks edelbrock intake and edelbrock carbs i am wondering why these engs never use pcv system? inoticed a lot of soot on choke plate. comming from valve cover vent hose too flame arester.so again i am wondering why not a pcv?thanks for any help

 

[Silvertip]

Re: p c v valve?

Are you old enough to remember when cars had what was called a "road draft tube"? In those days crankcases needed to be ventilated just like they are today. But back then blowby gases were simply vented through a tube that sent them down under the car. Pollution controls requirements required a closed system so manifold vacuum was used to suck the fumes from one side of the engine (on a V8 or V6) or one end of an inline engine. Fresh air entered the other side or other end. With our boat, you essentially have a PCV system but it works more like the road draft system than a PCV. Blowby gases are fed to the flame arrestor and then sucked into the intake. So the difference is that in a boat the fumes enter the manifold above the throttle plates. In a car they enter below. No big deal.

 

[dan t.]

Re: p c v valve?

Good question, actually most newer ones do have pcv. As a automotive mechanic with 40 years in the trade I also questioned the breather set up on boats, all it does is allow crankcase fumes to escape, the moisture and associated acids remain behind. On my current boat I actually had a valve cover rust out from the inside. That was it, I removed the carb, drilled and tapped the base and installed a pcv system, end of problem. FYI the pcv valve that seems to work best with a chev 350 is the A C # 774.