I'm in the process of pulling the head on my '72 240Z and on removing the exhaust manifold found long pipes extending into the head (photo attached).  I assume these were for a long-disconnected air pump (it was gone when I bought the car).  My question is should I remove them and do one of the hacks found in the topic:

 

http://www.classiczcars.com/topic/51171-keep-original-air-port-exhaust-manifold-or-who-cares/

 

or leave them be?

 

I can't imagine that they are any help to performance, but do they do any harm?  I installed a Motorsports premium exhaust system a few years ago, but otherwise run a straight, albeit, smog device removed engine.  If, if the cam needs to be replaced, which is possible because the oil tube clogged on me a couple of years ago, I probably go with a Stage I or Stage II cam of some sort.

 

SIDEBAR:  [i was lucky that the cam oil failure, good lord was that an absolutely horrible sound, came literally as I was pulling in to park at the end of my journey.  The unlucky part was that my journey ended 60 miles from home.  We diagnosed the next day and, perhaps with Mr. K watching over me while still on this plane, headed home after slathering STP on the cam.  Made a stop when I heard the slightest of noises, slathered more STP, and made it home. Those Nazi-era German scientists knew their stuff for sure.]

 

My options are to be:

 

1) Do nothing.

 

2) I don't know how to weld nor do I know anyone with a welder, so I'm leaning against going the welding route.  

 

3) Remove, then tap and install brass plugs.  Why brass instead of steel?  Better sealing because the brass will deform slightly against the cast iron?

 

4) Cut the tubes off inside the manifold, but keep the distribution (external) tube.  The thought here is that by removing most of the tube it would clean up the exhaust flow and no, or very little harm results from the connection to the distribution tube.  The tube would effectively become pressurized with the first exhaust pulse and that in turn would partially block new exhaust pulses from entering the tube.  At the least, the energy needed to push back down the tube the previous pulse would be less because the tube itself will be much shorter.  Does this make sense or would my labors end up accomplishing exactly the same outcome as 1), doing nothing?

 

Chris

 

P.S. I think I attached the photo, if not, look for a follow-up post with the photo.

 

 

 

 IMO, take them off. They do restrict the exhaust flow a bit. I think a lot of people cut and welded them because one or more wouldn't budge. The easy fix was to cut and weld them. If you can get them loose, I've seen them plugged with pipe plugs & bolts. Brass, steel or iron, any will work.   

The longer tubes can make removing the manifold while still connected to the down pipe a nightmare. The second time I went through this, I cut the tubes leaving about 1" protrusion from the manifold face.

I did this in lieu of removing the fittings which were frozen in place. Trying to remove the first one resulted in my cracking the tube just outside the fitting. With age and corrosion, I would not attempt to remove the fittings unless you are committed to go all the way and plug weld the holes.

Mine were rusty and had some holes, so they were gassing me with exhaust fumes. Had them cut off inside and welded shut, too rusty to (easily) get them out and plug them. Look better plugged, though.

Get rid of them, they mess with the swirl and flow.

I cut mine off with a sawzall, drilled the passages, tapped the holes and used a bolt. then welded the tops and bottoms.

You could just use a bolt and gasket, cheap and easy.

Edited October 20, 20159 yr by SurferD

Thanks for the replies.

 

The pipes will be coming out, or at the least, be cut back considerably.  I tried, with not much expectation of success, to remove the pipe fittings to make it a clean job.  Much to my surprise, the first nut turned without any drama.  Having been down similar roads before, rather than removing it, I went to the second nut -- a nut now well on the way to be rounded off nut.  Third nut, same as the second.  On to Plan B: I used a Dremel-like tool with a cut-off wheel to slice the pipes as close as possible to the manifold proper.  I may end up leaving it as is; with the distribution pipe still attached, there is no chance of leaking; but I'll haul it around town and see if I can get a shop to weld the holes shut for me for $20.  If so, I'll cut the pipes on the outside for a cleaner look.

 

Thanks again for the advice.

 

Chris