Inliners International Forums General Discussion Engines 292 pcv valve and breather location?

I have a 292 I am building (Mexican late model block and early model non-smog head already rebuilt and assembled) and have a Mercruiser valve cover to put on it. I want to run a PCV valve with breather system but on this valve cover the twist-in breather/filler hole and the push-in 1" PCV hole are only about 4-5" apart. Too close to get a good flow through the crankcase. Any suggestions on where else I could locate a breather? I could bore the valve cover for a PCV hole at the back end of the cover but that still leaves me with both on the same cover and maybe 16" apart. The link below shows the valve cover when I first got it. It has now been stripped and cleaned and will be painted. I have considered things like tapping the fuel pump block-off for a breather hose but as there is a Tom Lowe billet bracket there for the relocated motor mount that would be tough. Any suggestions would be appreciated.
https://picasaweb.google.com/sodell3/My292?authkey=Gv1sRgCMKLg53hsLrfXQ#5675754961228430626

The billet mount is plenty thick enough to machine for the breather hole.
You could put one on the rear side cover.

I installed a lot of PCV valves in the 60's when they became mandentory on Cali vehicles and we were required to "seal" the engine to the outside atmosphere. As I look at all my current vehicles it is still that way. I don't understand your idea to "flow" air thru the engine. Since the PCV valve sucks air into the intake below your carb this will cause a lean condition if I'm reading you right.

The PVC valve is manufactured to work in a negative atmophere. One of our old checks was to place a device on the oil filler and make sure there was a negative draft in the engine.

Negative is good. I run my racing engine at 9 on a 0-30 vacuum scale and use a pump to do it.....Good Luck

Yes, I was thinking of both of those. To do the billet drilling I would also have to drill through the steel mount. But it is thick enough to tap and mount a fitting on. I'll take a second look at it. Thanks.

Everything I've ever studied about the PCV system says you need to flow fresh air through the crankcase to remove blowby hydrocarbon contaminants and moisture. Air flows in through the breather and out the PCV. That's why on every V8 I've had the breather was on one valve cover and the PCV was on the opposite valve cover. Without a breather and only a PCV you will create great vacuum but you will be dumping all the blowby contaminants and moisture into your oil.
A racing engine does not need a PCV. A breather definitely but not the PCV. In your case using a pump to create crankcase vacuum helps sealing for sure. Great for racing.
A PCV can just as easily suck air into the air filter above the carb, not the manifold below it. The vacuum may be less but there would still be enough to flow the system.

Opps my bad. . . alligator/hummingbird.. I forgot about the second hose we put from the valve cover to the aircleaner and all the little air filters I replaced inside the air cleaners of those 70's Chev's. I remember removing all the draft tubes and sealing them and testing the PCV valves so they could not send a fuel mixture into the vapors of the engine..

I still suggest the use of a PCV valve to keep the "aroma" away from the passenger compartment and they do help keep the engine clean..The vacuum pump was a secret 20 years ago but not anymore.................JD

Yeah, I've run motors before with just breathers on them and all you end up with is a dirty smelly engine area. I'm definitely going to use the PCV. Just have to find the best place to put the breather. Too bad L6's didn't have two discrete valve covers.

I USE BREATHER CAPS IN MY OIL FILL HOLE EXCLUSIVLY WITH 0 PROBLEMS. ONLY THING IMO GOING DOWN A INTAKE MANIFOLD IS GAS AND AIR..... AND IF YOUR ENGINE BAY STINKS ITS BECAUSE YOU HAVE ALOT OF BLOW BY AND WILL NEED A O/H SOON.

Sodell, you are right about the V8 being able to pull the fresh air into one valve cover and the dirty air and moisture out the other side. That is the ideal situation, but not very practical for an inline engine. There are a few 4 cylinder engines with the PCV plumbed directly to the crankcase, but they are designed with baffles to keep the oil out and the air flowing.

The Chevy designed system of having fresh, filtered air from the air cleaner, enter the valve cover at the front and rear exit through the PCV valve to the intake manifold works quite well.

At the end of the day, a system that included a crankcase entry point would not keep the engine cleaner, provide cleaner emissions or longer engine life. You would just have a more cluttered looking engine.

I have never cared for the breater caps. They have a cheesy, cheap wire mesh inside that are impossible to clean. Fresh air from the air cleaner means when you clean or replace the air cleaner element, you are covering the PCV filtration as well.

Thanks for the advice. So, you think that if the breather was at one end of the valve cover and the PCV was at the other end that it would pull enough air that the crankcase would get some circulation too? Here's some pictures of my Mercruiser valve cover. Just click though them.
https://picasaweb.google.com/sodell3/292Mine?authkey=Gv1sRgCPXkrf2Zmp3lbw#5687557299774007362
It already has an oil fill and PCV hole. I could add a breather hole towards the back but don't know if it would be far enough away. Or I was thinking of buying a PES valve cover and having the holes cut at each end.
http://12bolt.com/250292_products/valve_cover
Steve

The 300 Ford has a baffle midway along it to divert much of the incoming fresh air through the crankcase and out the PCV port at the rear of the valve cover. Try that.

That is an excellent idea. You wouldn't have a picture of one, would you? If so send to sodell@rutgers.edu
If I built a baffle between the two it wouldn't much mater how close they were. Great idea.

Like this:

Just what I need, gives me a lot of ideas of how to do mine. My PCV hole is baffled and the baffle box surrounding it is held in place with 4 screws. Here's a picture of it from when I first bought the cover. It now has two boxes there (one for the oil fill cap) and is blasted clean. The one on the left is the PCV.
https://picasaweb.google.com/sodell3/292Mine?authkey=Gv1sRgCPXkrf2Zmp3lbw#5675755636352643282
It is dead in the center of the cover. I think I can braze a sheet of metal to it that will go side to side and top to bottom and achieve the same effect. It may have small gaps around the edges and some at the bottom but not much if I trim to fit. Or possibly weld in an aluminum wall in the same area.
Much appreciated.
Steve