[DeTomaso] Rocker installation
JDeRyke at aol.com
JDeRyke at aol.com
Mon May 17 13:49:58 EDT 2010
Rocker geometry changes with aftermarket parts is common,and its very
important to get it right before running the engine hard. Complete engine failure
sometimes results. Head thickness, gasket thickness, valve stem lengths,
rocker type and what cam you use all influence the geometry. FWIW, as Tomas
said, intake and exhaust valve stems are usually different lengths. Note that
this happens with all-stock parts if the heads have been at all machined,
even for a simple valve grind.
Get one adjustable pushrod to check the lengths you need. Adjustable
pushrods are not for running in an engine; ther usually aren't stiff enough and
are always too heavy. Use a felt pen on a valve stem tip, assemble that
cylinder and roll the engine thru two complete revolutions; the tip will scrub off
the marking ink and you'll clearly see the contact area. Then you can order
the correct length pushrods. or have some made up locally. Remember, they
must still be hardened on the upper ends. There are lots of cam tech sites
that explain whats going on here, and how to correct it by varying pushrod or
valve stem length. Good luck- J Deryke
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