Smoking exhaust

steve ,when you do a valve job there should no HOT GASSES COMING TO THE TOP END (valve cover area) if there is it's blow by from the top end, piston and rings ? WTF
is that how you rebuild engines?

Are we talking about hot gases coming from the exhaust headers into the cylinder head above the valves and then through the valve guides to the area under the valve cover? I ask because the 4 into 1 exhaust was mentioned, and I suppose there could be some pressure coming from the exhaust system into the head (above the valve) for any cylinder not on the exhaust stroke. Ed

'With the 4/1 exhaust the pressure is more or less constant'what does that mean?are you on meds?i know you are retired but being a senoir member here we have a responsibility to educate the young rookies .we have to separate fact' s from fiction.being a master toolmaker for 37 years i had a lot of young guys that served there apprenticeship with me in the tool room.i give the most accurate info that i haved learned from the "old masters"lets pass down real world info that they can pass down.

I don't know what you're reading into this but I stand by my statements. Yes hot gasses CAN get by valve guides and worn/broken seals overheating the head. Rings can do this too but the barrels are in the bottom end where the collector/vent is. Most of it escapes through the vent. I've been wrenching on various machines for 40+ years. It's my experience with vintage bikes, especially if they've been sitting, the first thing to replace is the valve seals. If you're in there, the rings. Like I said, depending on the condition of the valves, guides, cam chain components and cylinders, a complete overhaul may or may not be indicated.
Ed, yes, with separate pipes the back pressure pulses, a 4/1 equalizes all the cylinder back pressure so there is no negative pulses. While this creates more ponies, some of this can get back through the valve guides while the valve is closing.
810, no I'm not on meds. I WAS trying to point out what to look for while in there. You're right, no gasses should be in the head and that's NOT how I build engines. If you'll read my post again you'll see that is not a problem in a healthy engine. :whistle:

BTW, most vents ARE located in the valve cover, I wonder why?

Swest what do you mean by vents? Can you include a picture? I'm not sure what you are referring to. Not doubting just don't know much about anything. I always thought it was a closed system apart from the oil vent, intake controlled by valves, exhaust controlled by valves, and external exhaust using back pressure.

That's what I was talking about. The oil vent on top of the crank case. It has a collector drum which is a good idea. Why others replace them with cut down versions baffled me. They don't look bad, at least to me, it is after the filter, so that's not a problem and getting the hot gasses out of the engine is good for the rubber parts. Most have the vent in the valve cover for auto, truck or motorcycle for decades. If there's that much "blow by" it's time for a rebuild anyway. My old 2/1 pods had a port for the vent to comply with the less stringent emissions of that time. Guys would and do put a filter on there because it's cool or they like the idea of getting away with something. It's called positive crank case ventilation and it's there for a reason. As I said, "in a healthy engine, it's not a problem".
Steve

I thought about plugging the holes that go to the smog gear. I thought that might cool stuff down. Right now I have them linked together.

The smog stuff is a different story. I never liked the idea of injecting air into the exhaust ports. Prone to fail. If removed, then carboration can be an issue. I don't know enough about how to do it and like in a car in the Socialist State of California, you can be pulled over for a smog check and loose what you're driving or pay hefty fines for doing it. They started the PCV system in 66 and my 69 Ford F 250 has two, one to the intake with a PCV and the other to the air cleaner. Hasn't been a problem in 25 years I've owned it.
Steve