To vent or not to vent?

[Thundarr]

Whenever I run my AC full blast and recirclate the cab air, I seem to be pulling in some exhaust smell. I don't smell it when I am moving above 20-30 mph. It's only when I slow down or sit in traffic. The PO put in an 80's era GM Goodwrench 350. Here is a picture of the current setup. I have a PCV from the drivers side valve cover connected straight into the carb and then a filter on the passenger side valve cover. There is no charcoal canister.



I recently put in shorty headers so I know the exhaust is all connected up well but the smell still persists. I did just find that I am missing the boot over the brake lever that goes through the firewall which could be sucking in some of the engine bay/crank case vented fumes.

I have ordered and will install a new boot on the brake lever to better seal up the firewall, but I also ordered a charcoal canister and plan to properly add the "T"in the hose from the drivers side PCV to the carb and then over to the canister.

So now getting to my question, what do I do with the passenger side filter? I have noticed that a lot of setups don't have a filter on the passenger side. Should I:
A.) plug it?
B.) switch it to another pcv and "T" it into the the line to the canister also?
C.) just leave it be and hope the boot fixes it?

[davepl]

You might want to fix all that rubber fuel line - just something I post any time I see more than a foot or two of hose.

How are your fenders behind the front wheels for rust, esp on the passenger side? I'm wondering if it's pulling exhaust in through the cowl vent perhaps.

[68is4me]

The PCV valve should have nothing to do with exhaust smell in the cab. The way it is hooked up should be just fine.

The canister is used to catch and recycle the fuel vapors from the fuel tank.

Are you running complete exhaust all the way to the rear bumper with no leaks? If you are, you should not be getting much exhaust smell in the cab. If you exhaust is shorter and comes out somewhere under the truck that would be your problem.

These cabs are not sealed vary and have leaks all over.

[Thundarr]

Originally Posted by davepl

How are your fenders behind the front wheels for rust, esp on the passenger side? I'm wondering if it's pulling exhaust in through the cowl vent perhaps.

The fenders are in good shape.

Originally Posted by 68is4me,

Are you running complete exhaust all the way to the rear bumper with no leaks? If you are, you should not be getting much exhaust smell in the cab. If you exhaust is shorter and comes out somewhere under the truck that would be your problem.

These cabs are not sealed vary and have leaks all over.

Yes, the exhaust is run all the way to the back and even turned down at the tips under the bumper.

Sounds like I might just really need the boot behind the brake booster.

[Bigdav160]

Theoretically, the crankcase vapors ARE exhaust. But the vent is the intake side of the crankcase ventilation system. In your case the vent side could be routed to the air cleaner base. There is usually a knock out for this purpose. New, the open air cleaner probably had the attachment also.

[Tom Vogel]

Why don't you just stuff something behind the broken brake boot temporarily to see if that's really it?

[Thundarr]

Originally Posted by Tom Vogel

Why don't you just stuff something behind the broken brake boot temporarily to see if that's really it?

Duh, thanks Tom. Probably should have done that first. Oh well, the boot was in bad shape and on its way anyway.

Look what else I discovered. The after market air cleaner base doesnt even seat onto the carb. It hits on that rised portion the left side and kicks up the cleaner about a quarter of an inch no matter how I orient or how hard I press. That MUST have something to do with the smell.




New question, can you help me identify what Edelbrock carb I have so I can get a correct air cleaner?

[Thundarr]

Nevermind, looks like they are universal, but even better, they have an adaptor/spacer the will fit and costs $6.47.

[swamp rat]

That or find an air cleaner base that's more flat, i run the Edelbrock aluminum assy that fits the carb just fine.. Don't run 2 pcv valves.

[kilrcady]

ball valve on heater hose?

[Thundarr]

Originally Posted by kilrcady

ball valve on heater hose?

Yessir, one of the best and easiest upgrade for hot climate trucks with AC. The old vacuum operated shutoffs never really close even when new.

By the way, I figured out my smell issue. Adding the spacer on the air cleaner knocked out 90% of the smell. I guess I was drawing in straight fuel vapor because the cleaner wasn't sealed to the carb.

[volksworld]

that air cleaner base is the old moroso style...designed specifically to fit holleys and wont clear an edelbrock performer....the bump outs were to clear the float bowls on the holley....it was designed to drop a large filter element as low as possible for hood clearance which obviously isnt an issue on our trucks

[dflarsen77]

I use a 2" spacer on my edelbrock carb and my air cleaner is a pretty low drop like yours. Glad that worked out, although I'm kinda surprised that was it.

Anyways, you def need the breather filter on the passenger side. The pcv runs to the carb and basically sucks the gas out of the crank case, and the breather is where the air gets in to allow that. Originally, they had a big tube off the air cleaner that ran to where that breather is, and used a flame arrestor. So yours (and mine) I think is referred to as an open system because it pulls air from the atmosphere. But you can get a breather with a little port on the side, and then an air cleaner with a little port that can be added, and run a hose between them and then it's a closed system. I think running it that way might be better because it will push more air in, but I really have no idea.