Inliners International Forums General Discussion Engines Getting the stink out

My 67 250 originally had a PCV and a tube to the air cleaner. Upgrade with holley 4BBL, still have PCV, but no tube to air cleaner, but filtered vent to engine compartment.

Car smells pretty bad, especially bad if i open the hood.

Would most of the stink go away if i ran a tube from valve cover to air cleaner?

Perhaps. The stock setup lets those blow-by gases vent to the snorkel air cleaner, when there is no vacuum to the PCV valve. Which I guess keeps it contained as opposed to just the valve cover filter vent which lets it out into the engine bay.

When I got my Camaro, it smelled up the garage of gasoline. I eventually noticed that the hose, going from the EVAP canister to the metal vent tube to the fuel tank, was disconnected and venting the tank openly. Plugged it in and it cured the smell. Did you leave the EVAP canister connected too?

Theres no EVAP on the 67. Retrofit worth it?

I used to have a lot of positive pressure in the tank. New muffler seems to help, my theory was i had a little leak, but im not certain.

My old 32 had a vent tube sticking down with angled cut on backside to get venturi vacuum. Surprising that it works at 25 mph. Smell was worse.

Hmmmmm......I thought that the EVAP went on when they removed the vented cap on fuel tanks. Doing some Googling, it looks like 50 state EVAP was in 1971. Without an EVAP canister, how did a non-vented gas tank work then? Is there a pressure valve on it?

I don't know how you retrofit an EVAP on an older carb? The factory EVAP hooks to the Monojet fuel bowl and fuel tank to passively capture fuel vapor. It runs timed (or ported) vacuum to the temp valve on the water neck which it shares with the EGR. Once the engine is warmed up, it allows the vapor in the EVAP canister to be drawn in through the manifold port that is shared with the hose to the PCV valve. I presume the older carbs (like the non-emissions aftermarket carbs) have fuel bowls with open vents, so you can't hook the EVAP hose to the carb?

I've got Holley 4BBL on it, timed vacuum port is free.

Is the vented cap one way vented or straight vent? I had it in my head it was one way. If its a straight vent, mine is misbehaving.

I thought that by '67 they had stopped using vented caps, and used used ones that seal tight like my '78. But on my '78 I have an EVAP canister with a line to the tank, so expanding gasses have somewhere to go. I'm reading up on the '67 to '70 Camaros, and it seams that the cap is a one way vent allowing air to come in, but not for vapors to escape. And there was a return line attached to the fuel filter I think to control carb vapors? Prior to the sealed tanks, they were just open venting which contributed fuel vapors to smog.

Yeah, your Holley has two upward vents sticking up from the bowls. There's no easy way to hook them up to an EVAP canister. But I suppose you could use a V8 one that is missing the carb valve on it, and just hook it up to the timed port. You would need the thermal valve for the water neck that is for the EGR/EVAP, and another port on the neck to screw it into. That would provide the vacuum to the canister valve. Then you need a line back to the fuel tank. But I don't know if there is a vent pipe to hook up to on the pre-EVAP tanks?

Looking at the engine today, my PCV/oil filler cap is pretty loose. There's a bit of oil leak, probably burning and contributing to the smell.

Gbauer used blacl tape to tighten his cap up. I might have to try that too.

Mark

It was black tape and black RTV but I always suspected it was really the valve seals that were the real issue. Wasn't your head recently re-worked?