Big block Chevy heads

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 [[File:Bbc 702 cc.jpg|thumb|Closed chamber,c/n 702 shown]]
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+==Exhaust valve guides==
+{{Note1}}The following is an excerpt from an AERA technical bulletin:
+'''Exhaust Valve Guide Caution On 1965-98 GM Big Block Engines'''
+These engines' valve guides were not intended as a replacement item from GM.
+The guides were located into the head castings after the head was cast and
+the exhaust guide is "water cooled".
+The water-cooled guide also has two different size press fit diameters. Adding additional confusion to the matter, they also switched the location of the larger diameter sometime in 1985.
+To determine which outside diameter guide you have and which direction to
+remove an exhaust valve guide, the following procedure is suggested:
+Drive the guide no more than 0.250" (6.35 mm) toward the valve spring side of
+the head and stop. Then, measure the newly exposed area of the guide
+OD next to the spring pad.
+If the measurement is 0.620" it is the first style guide. To remove this
+style guide, continue driving it toward the valve spring side of the head.
+If the measurement is 0.616" , it is the second style guide. To remove
+this style guide, you must drive it the opposite direction toward the combustion
+chamber side of the head.
 ==BBC L29 Vortec heads==

Latest revision as of 05:40, 28 June 2013