67 small block K-19

[Dale S.]

I drove my 67 to coffee this AM. 67 sb with K-19 and C-60. I noticed when I wind it up a little (4500 RPM), when I back off I get a popping in the tail pipe(almost a cracking). Stock mufflers, has anyone noted this? I seem to remember a post on this but can not find it in the archives. Dale

[Douglas L.]

Re: 67 small block K-19

Dale,

I would probably start with a close look at the carb to make sure it's working right. If it's running too rich, that's going to cause a problem and can cause the popping.

On an A.I.R. car, the way the system is designed to work, you step on the gas, the A.I.R. pump is sending air to the backside of the exhaust manifolds through the check valves on each manifold. This helps burn unburned exhaust. When you let off the gas, the diverter valve which is next to the carb diverts air into the base of the carb leaning out the mixture. If the mixture goes into the motor too rich, you will get popping.

Here is how I have checked the diverter valve on my car. Remove it and hook a vacuum pump to the vacuum hook up. Try blowing into the valve hose inlet that comes from the A.I.R. pump. If air goes through the valve, then its not working correctly. If air does not go through the valve, then blow on it and squeeze the vac pump. The vac pump should allow a burst of air to go through the valve.

You also want to make sure the check valves that go into the manifolds work right. Air should flow down to the manifolds, but not the other way.

On dirty check valves and diverter valves, after cleaning them with lacquer thinner, the system on my car works great.

[Dale S.]

Re: 67 small block K-19

Thanks Doug. I know the check valves are good. They were checked after Jerry replated them (thanks again Jerry). I have a hand held manual Vacuum pump. I will check the diverter valve. You cleaned it with lacquer thinner? No rubber parts in it? Thank you for your help. PS the carb is fine and car runs great. Dale

[Douglas L.]

Re: 67 small block K-19

Dale,

I did use lacquer thinner and it worked. But, I did try it first on an old diverter valve off a 6 cylinder motor(#545) first. A safer choice would have been kerosene which is what I will use if I ever do it again. I know there is a plastic piece on the inlet side of the valve and there is also a baffle inside. I do not know what the baffle is made of.

Check out this website: http://www.camaros.org/emissions.shtml

It has some good information on the A.I.R. system.