My hangar mate races rotaries and his buddies and engine builders 
started asking how to get this "magic" stuff.  Aircraft Spruce is the 
place.
Send all royalty checks to my Paypal account, or I'll sue!
Buly

 

 

If your flanges are truly flat, you can use a 1/4" thick bead of 100% GE silicone about 3/4" outboard of the port. Bolt on the header and forget it. The silicone extrudes down to near

zero thickness in service. It has never leaked. It is not exposed to pressure even with a high flow muffler in place. The high velocity at the port means low pressure. If the seal fails, air will leak into the exhaust system and make a popping sound on closed throttle.

 

Works great. Lasts until you remove the headers again. Cheap.

 

Lynn E. Hanover