68 up 6 cyl air cleaner?

[martindc1]

On a 68 and up 6 cylinder air cleaner, where does the hose from the valve cover plug into? What does the fitting look like? Any pictures? I'm talking about the air cleaners that are mounted above the valve cover and they have the connector that goes over to the carburetor.

[rabbitjaws67]

had a 67 - 250 ci had a hard tube then a rubber hose from pcv to bottom of carb hope that helps

[martindc1]

Yes, the 68s and up had the same PCV setup but with an additional hose that went from the side of the valve cover to the air cleaner box. The purpose was that the PCV system would suck the fumes through the PCV valve and into the intake and this second hose would allow filtered air from the air cleaner to enter into the crank case.

[fishingjred73]

Here's a pic of mine not the best but all I have at the moment

[martindc1]

Ok so the hose from your valve cover goes into the tube on the top of the carburetor, that's what I wanted to know. Is it a metal bung welded to the side of it? My 67 and earlier air cleaner is the same setup, except there is no nipple on the side of the tube on top of the carburetor. Wonder if they were all like the one in the picture?

[martindc1]

BTW, thanks for the pic!

[fishingjred73]

I know it's original, but it's been so long since I actually looked at it I don't really remember how GM made it. I'm at work till tomorrow morning so If no one post up a better pic before then I'll get you a close up when I get home.

[pritch]

Is it required or best to have this? I dont have the hole in the valve cover. Would that be a newer or older VC?

[fishingjred73]

Mine is original '68 vc.

[RichardJ]

The purpose of that tube is to provide only fresh air that has been filter through the carb air cleaner. If you just use one of those mesh screen caps in the oil filler hole, they only stop the big chunks from going into the engine. The other reason for that tube is that if the PCV vacuum is not strong enough to pull all the crankcase fumes into the intake manifold, the excess fumes will go out to the top of the carb where they will also go into the engine and be burned up. During WOT the manifold vacuum is low and the PCV system may not be able to pull all the crankcase fumes. This is called a closed PCV system because no fumes can escape and are all burned.
It is hard to see in my picture, but there is a device in the middle of that rubber hose called a flash suppressor to keep any carb backfire flames from reaching the engine.
You can also see that I made a new metal tube above the much larger Carter AVS throat. Changes also included cutting open the area between the two wing nuts and modifying that passage for more air flow.
It was more work than I should have spent on it, BUT I like the semi original look.


I should mention the truck is a '67 3/4 GMC. The air cleaner, tube and valve cover were original to the Rochester B with man choke on this 292. I don't know if any of that makes a difference, but this '67 had that tube as part of the PCV system.

[NGN]

Sorry to jump in on the thead but, I was wondering if my 67 two - fifty would need that extra air passage going to the front on the side of the valve cover. Mine only has the PVC hook-up, up top in the back. I went power brakes with the booster so I now got a off set air filter assembly off a 72. I was thinking of just capping off the tube that comes off the air filter assembly base or do I need that extra breather ?

[N2GMTrux]

RichardJ- I would just like go say that is slick. When I first looked at the picture of your engine setup it looked original. Then I noticed the larger tube over the carb, then I noticed the offset of the carb. That's a great job at try'n to hide the cool modification looks good.

Thanks for the pic
N2GMTrux
S. Chavez

[martindc1]

My 67 250 does not have that extra tube as a part of the PCV system. It is pretty worn and has a lot of blow by. With the original oil cap, under a load, it will blow some oil out around the the main seals. With one of those vented caps, it fills the cab up with crank case fumes going up a hill. I just bought one of those breathers with the nipple on the side to affix a hose. Currently I have a hose routed down into one of the wheel wells like an old school road tube to vent the fumes under a load. However, I would like to either find an original piece to the air cleaner or modify my existing tube to take the hose. That's what I was getting at.

So NGN, I would say yes, that extra tube is important. An easy fix would be to get a push in breather with the PCV nipple on the side. I believe mine is made by Mr. Gasket. There are also twist-on versions available that would go right into your oil fill hole, though they are harder to find. However, Jegs has them. I just got the push in type, mine came with a grommet that fit right into the oil fill hole.

[martindc1]

BTW Richard, that is a nice setup. Looks really good. I for one can't stand chrome air cleaners, and your setup is right up my alley.

[54blackhornet]

Richard, your 292 pvc system seems to be a lot different then the one on a stock 250 ? I have a 68 GMC 1500 that came with a 250, i replaced that with a 292 I built up, it runs fine with the stock 250 monojet carb & valve cover in place. I did rout the pvc hose to the intake manifold. My question to you, is that a stock GM carb & air filter for a 292 and if so what year ? I would like to switch over to that setup...........Great Job

[RichardJ]

The PCV system is the same as was originally on my '67 292 and is the same as the one in the picture "fishingjred 73" has posted.
Filtered air enters the steel extension above the carb and travels down the rubber hose to the front, side of the valve cover. The air passes through the crankcase and the valve cover and mixes with the crankcase fumes. The air and fumes exit the rear of the valve cover through the PCV valve. A hose from the PCV valve connects to a vacuum port on a stock intake manifold, in the middle, center behind the carb . The Clifford intake does not have that port. The Carter and Edelbrock clones have a PCV port that just dumps into the base of the carb below the throttle blades. SAME THING.

The Clifford does provide a location on the top, rear that can be drilled and tapped for a vacuum port. I did that, but used it for the brake booster.

Is that a stock GM carb? It would be a stretch but I could say yes, but not on a 6 cyl. I would have to look it up, but in '66 or '67 Chevy used a Carter AVS on a 327 V8. This particular carb actually came from a '70 340 Mopar.

[awc7772000]

i have a 1970 292 and there is 2 hoses on mine there is one going to the air cleaner which provides a "breather" and theres a filter in mine and then there is a pcv hose that comes out and "plugs" for lack of a better word into a fitting on my intake manifold hope it helps you

[fishingjred73]

Here's a couple more close ups.

[NGN]

Thank you martindc1 and others for info and pic's Nick.

[martindc1]

Wow thanks for the pics!

[54blackhornet]

Thanks for all the 292 carb info