Where do these smog tubes go?

[Lawrence S.]

I put a Bill Hodel smog setup on my 69 L71 and not sure where these tubes go. My original smog manifolds are on the car so did not remove them. I am guessing these tubes go in the exhaust manifolds? I have eight of them.

Thanks

Lawrence

[Mark E.]

Re: Where do these smog tubes go?

Are they AIR injection tubes that slip into the exhaust manifold ports?

[Lawrence S.]

Re: Where do these smog tubes go?

Yes that is what I think too Mark but was not sure. When I tried to slip them in the manifolds they would not slip in because I think the originals are still in the manifold. I could hear something moving in the port as I was trying to get the tubes in the manifold.

[Joe L.]

Re: Where do these smog tubes go?

Yes that is what I think too Mark but was not sure. When I tried to slip them in the manifolds they would not slip in because I think the originals are still in the manifold. I could hear something moving in the port as I was trying to get the tubes in the manifold.

Lawrence------


Yes, that's what they are. They are the tubes that slide into the AIR ports on the exhaust manifolds. However, to insert them you, of course, have to first remove the old tubes. That won't be very easy with the manifolds installed on the engine. These tubes usually have a significant build-up of very hard combustion products especially on the inner ends. Removing the tubes without first removing the combustion products is usually well nigh impossible. Of course, the manifolds need to be removed before the cleaning can occur. With the manifolds off the engine, the bulk of the combustion products can be chipped off. Then, the tubes can be driven out with a hammer, shearing off the remaining combustion products in the process.

[Lawrence S.]

Re: Where do these smog tubes go?

Thanks Joe.

[Mark E.]

Re: Where do these smog tubes go?

Or just neuter the pump, leave the old ports in place, then hook everything up so it looks stock.

[Lawrence S.]

Re: Where do these smog tubes go?

The car has 27K miles on it as far as I can tell. I left the tubes in the manifold and hooked everything up. If I have issues then I may take the tubes out or neuter the pump.
My original 69 L-46 pump I had Bill neuter.

[Michael B.]

Re: Where do these smog tubes go?

The intent of the AIR system is to inject additional air at the exhaust valve where unburned fuel is hot enough to continue to burn with the help of a little additional oxygen. Don't neuter the pump. Without air flow, exhaust heat will travel up the injection manifold and burn the check valves and hoses. Also the injector manifold nuts are flare fittings, not pipe plugs, and will not seat and seal without the tubes in there. If it's not leaking, the tubes are in there. If you are able to remove the injection manifolds without twisting the tubes, try inserting a drill bit that just fits inside the tube and wiggle it around in a circular motion to see if you can break them loose from any carbon build up. After you get them loose, You might be able to extract them with either an appropriately sized wood screw or a screw extractor.

[Mark E.]

Re: Where do these smog tubes go?

Good point about exhaust traveling up the injector manifold if the pump doesn't pump.

Lawrence may have a good plan of just leaving the old tubes in the exhaust manifold and avoid the issues with removing them.

[Joe L.]

Re: Where do these smog tubes go?

The car has 27K miles on it as far as I can tell. I left the tubes in the manifold and hooked everything up. If I have issues then I may take the tubes out or neuter the pump.
My original 69 L-46 pump I had Bill neuter.

Lawrence------

If the car actually has 27,000 miles the tubes will be fine. In any event, I absolutely do not recommend disabling the AIR system in any way.

[Duke W.]

Re: Where do these smog tubes go?

Those internal tubes are quite restrictive to exhaust flow and cause a noticeable loss of power in the upper end of the rev range. I noticed this after removing them from my Cosworth Vega's Pulse Air Injection System (PAIR). Others CV owners noticed the same thing, and there was no problem passing emission tests without those internal tubes.

Duke

[Lawrence S.]

Re: Where do these smog tubes go?

Prior to installing the tube trees on the manifolds the tubes in the manifolds were loose enough in the manifolds that I could here then moving within the manifold.
Joe, I agree 27K miles seems low. Due to the 4.11 rear, original paint, and normal wear parts still in place it just points to low mileage but I really don't know. I don't plan on removing the smog system. I once owned a 69 Z28 with original smog in place and it seemed to work well.
Mark, I can't remember who told me to do this, but I have used roofing nails inverted with the head creating a perfect seal on the tube coming out of the tube trees. This is to keep the hot exhaust from traveling up the to the valves and ruining them.
Duke, thanks for the info on the removal of the tubes.

[Jeff S.]

Re: Where do these smog tubes go?

Flat head socket/allen drive machine screws, stainless steel (12-24, I believe) is an alternate method to create a seal between manifold AIR ports and the rail nut.

[Ryan S.]

Re: Where do these smog tubes go?

Are these tubes required or can you connect to the manifold without them? Do the rails not create a good seal to the manifolds by themselves?

[Duke W.]

Re: Where do these smog tubes go?

If the internal tubes are not present the threads may bottom out in the exhaust manifold before a good seal is formed or they may tend to loosen. You can always cut down the internal tubes so nothing protrudes into the exhaust stream. The judges will never know, and likely neither will the emission tester.

BTW, always use a tubing wrench when loosening or tightening the B-nuts on the AIR manifold. A conventional open end wrench will likely round off the hex. A film of high temperature anti-seize is also a good idea.

Duke