I do not market carbon fiber pushrods for the air cooled VW engine because they have "0" expansion rate and the VW engine will have up to 0.030" growth at normal head temperature. At maximum it could have up to 0.080". When we originated the carbon pushrods and experimented with them in 1981 and 1982 on our race and street engines, there was simply no way to maintain proper adjustment from cool to hot. Not even when we set the valves at zero lash cold. In fact, after only a little running with zero lash, we had problems with some of the valves getting tight, leaking and had to re-adjust them prematurely. In our race engines we often had 0.050" to 0.080" valve lash at the end of the quarter mile. They provided no benefit for the engine other than they were quieter than metal ones when run with excessive clearances. Flex was considerably more than that of our chrome moly steel. |