Speedex Heads

[Steve kay]

This makes interesting reading, but for this simple soul leaves some unresolved questions. I put a hc head on my Ruby but it made such an increaed racket that I soon put the lc head back on. I was worried that the noise was from the bottom end, but one contributor suggests pistons rather than bearings. The head is marked 1A911 and AF2, whatever that says about its origins. I am aware of how much gas flow contributes to performance as the first tuning on my 2CV were Pete Sparrow gas flowed heads making an immediate and noticeable improvement. So the question is does a Dave Dyer head improve gas flow or raise compression?  Speed is not important for shopping or nav rallies, reliabilty is paramount. Unthreatening performance improvement is always desireable however.