The cracks are thermal fatigue cracks that develop due to the excessive heat
that builds up from an engine that is designed to run at the extremes of
leanness.

SEE:

http://www.hpcoatings.com/exhaust.html

http://swaintech.com/header.html  (I got all my parts: heads, head sealing
surface, pistons, bearings, valves, coated here.  Exhaust coating cost @200.
)

I coated the stock 2.1L exhaust plus internal parts so that more of the heat
from combustion to be channeled out the tail pipe.  The entire engine
compartment will now be about 40 degrees cooler (reduction in radiant heat),
so now all the rest of the compartment components will last longer.

Coating the exhaust, either stock, SS header, stainless steel, should be
considered to reduce the risk of thermal/stress cracks.

Robert

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