I am currently cleaning up a 73. I have to do the exhaust - it's about to turn to dust and looking down the road I am thinking about a street (midrange) cam, so working backward I figured I should start with a header and a 2.5 exhaust in order to acount for the future intentions.

Anyway I just ordered a coated header 3-2 and 2.5 turbo exhaust at MSA. Now I am scratching my head (top my shoulders - NPI), after reading this thread and Carl's comments.

Hope I did the right thing - shipping was over $100. Sucks to have to order everything cross country.

*A local circut racer cut the tubes close to the studs and crimped the tubes closed. The car was not used extensively after that so I can't say how well it worked out.

"Cutting the stock exhaust pipe open at the "Y" and going to a larger diameter exhaust system, with a free flowing muffler will pick up between 12 and 15 HP. "

Mr Beck,

What exactly did you mean by this? Are you referring to the divder in the neck of the exaust manifold itself or something further down the tube?

I've never seen a stock setup so forgive my ignorance,

Best,

H Houghton

Here's a pic of the exhaust air tube plugs I got from McMaster-Carr. They are 1/4" BSPT hex head and I think they look pretty nice.

With that big hex head, I'll be able to remove them if required...

Just for reference, anyone planning on tapping the holes out to install the original air galley should use the ¼”-19 BSPP tap. The BSPT will not go deep enough to allow you to start the threaded fittings of the air galley. Unfortunately, I ordered the BSPT tap and the fittings will not start into the holes. Got out my calipers and found that about half way up the tap, the thread max OD is 0.537”. The air galley fittings are 0.542” OD and will not thread into the smaller diamter. The upper portion of the tap is 0.545”, so that part will work. I will take a die grinder to the tap this afternoon and cut-off the lower, smaller diameter portion of the tap. This should make it possible to tap the hole to the right diameter, instead of popping another $20 for the BSPP tap. The tap can be purchased from McMaster-Carr as discussed earlier here.

Cut the bottom 1/3 of the BSPT Tap and it worked perfect. Was able to run tap all the way into the hole. Attached the air galley into the manifold using some anti-seize copmpound for lube. Will install assembly in Silver Z today or tomorrow.

Just for reference, anyone planning on tapping the holes out to install the original air galley should use the ¼”-19 BSPP tap. The BSPT will not go deep enough to allow you to start the threaded fittings of the air galley. Unfortunately, I ordered the BSPT tap and the fittings will not start into the holes. Got out my calipers and found that about half way up the tap, the thread max OD is 0.537”. The air galley fittings are 0.542” OD and will not thread into the smaller diamter. The upper portion of the tap is 0.545”, so that part will work. I will take a die grinder to the tap this afternoon and cut-off the lower, smaller diameter portion of the tap. This should make it possible to tap the hole to the right diameter, instead of popping another $20 for the BSPP tap. The tap can be purchased from McMaster-Carr as discussed earlier here.

Was there a reason you had to tap the holes at all? Wouldn't the new air galley bolt right in?

I just sent out my exhaust mainfold to be ceramic coated and I was figuring I may need to tap the holes once I got it back so your experience with the tap will be very helpful.

I just cut the air tubes out and welded the holes shut. After grinding down the welds and repainting with exhaust paint the thing looks like a new stock part

When I did mine, I found bolts, not plugs. I locktight'd them in, cut them with a cutting disk on a dremmel and ground them down with a grinder. After which I painted with POR-20. Pretty happy with it...

Gallery Link

My brother-in-law (84 Corvette, 56 Ford Pickup) works for Zep, and he gave me this product called Groovy and it works great. I took my 10/70's brake lines apart with it with no kinking! Just sprayed a little on it the night before, went back the next day shot a little more and whola, like a hot knife through butter.

When I did mine, I found bolts, not plugs. I locktight'd them in, cut them with a cutting disk on a dremmel and ground them down with a grinder. After which I painted with POR-20. Pretty happy with it...

Gallery Link

Is that the "original" colour of the manifold? I've been planning to paint it with something, just dont know with what. Its rusty-poo'ish looking now.

Is that the "original" colour of the manifold? I've been planning to paint it with something, just dont know with what. Its rusty-poo'ish looking now.

The POR-20 looks almost identical to the color of the steal when it comes out of the sand blaster, so I guess its a bare steal look. You have to cure the paint so I popped it in the oven when the wife was out running errands, then ran a self clean cycle... "Hey honey, I cleaned the oven!" :laugh: