Aluminum heads are especially vulnerable to warpage and cracking because aluminum has a much higher coefficient of thermal expansion than cast iron. Consequently, when a bimetal engine with an aluminum head gets too hot, the head tends to swell up in the middle, causing it to warp and blow the head gasket. If the engine has an overhead cam, the resulting misalignment in the cam bores created by the warpage can gall or seize the cam bearings, or even break the cam. Anytime you encounter a warped or cracked aluminum head, or an OHC head with a seized cam, chances are the damage was caused by overheating.In some engines where the center exhaust ports are siamesed together, hot spots can develop in the head between the exhaust ports causing the head to swell so much it crushes the head gasket resulting in a blown head gasket. Replacing the head gasket may temporarily solve the compression problem, but unless the underlying cause of the elevated exhaust temperature is diagnosed and corrected, the replacement gasket may eventually suffer the same fate. Some aftermarket gasket manufacturers have gone so far as to develop special reinforced replacement gaskets for engine applications that have a history of crushing gaskets.
Sincerely, Ryan Lewis [email protected] AIM: vwjetta90 Red '90 16v 2.0 GLI Silver '00 GLX VR6 '90 Black/Blue Suzuki GSX-F600
