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Head w/AIR holes, plugging question
https://slantsix.org/forum/viewtopic.php?t=10832		 Page 1 of 1
Author:  JohnnyDees [ Sat Nov 06, 2004 5:19 pm ]
Post subject:  Head w/AIR holes, plugging question
I know this has been asked before but I cant find it. I have a 1977 head with the air injection holes in the exhaust ports by the valve guide. I am planning on porting this head and would like to plug these holes. Has anyone done this? What method did you use? Also does anyone know what the Exhaust temperature is in this area?
Author:  Guest [ Sat Nov 06, 2004 9:26 pm ]
Post subject: 
i dont know about anyone else, i just drilled, tapped and plugged the large exit port. heh
Author:  Doctor Dodge [ Sun Nov 07, 2004 3:01 am ]
Post subject: 
The factory used a cup plug to seal-off the main port at the rear of the head. I have also seen a factory made "dummy cover", it looks like the Air Injection tube flange with no thru hole, it uses the same gasket and bolts-on.

If you really want to plug the hole in each port, tap the holes with a 1/4 - 20 UNC tap, go in about about 7 turns using a taper type tap, not a "bottoming" tap.
Now find some "soft" 1/4 bolts. (cheap "no grade" hardware store bolts will do) screw them in until they bottom-out, then keep turning until they break-off. :shock: Grind flush as needed.

As for temps in the port, the hot exhaust gas can reach 1400-1600 degrees. The metal in the ports walls stays much closer to cooling system temps, maybe seeing 400 to 500 degrees in the hottest spots along the port's surface.
DD
Author:  JohnnyDees [ Sun Nov 07, 2004 4:59 am ]
Post subject: 
Thanks Doc , I was thinking of tapping and using JB weld it is supposed to be good to 600 deg. I thought maybe the threads would hold it in place. But maybe Ill try the broken bolt method.
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