Originally posted by DemonSVT:
.5mm is a 5.1% increase in lift (9.8mm max lift - all Duratec cams)
A 9.2% increase including rocker ratio.
That's huge on a multiple overhead cammed engine. In my opinion...
Including the tight clearance tolerances it may be the limit as well???
D'oh!
That's what I was missing. I forgot the cantilever of the rocker arm and it's unequal arms - hence the multiplyer. For some reason I was think og direct acting buckets, like on my old VW 1.8L motor, which on that type of cam/valve system, would mean that 0.5mm would be miniscule.
Terry it all makes sense now......
I agree this has to be tried as it is a fraction of the cost of making hole new cams, and if done right would be just as good. The key is making sure the shaft are heat treated correctly, and then "trued" up afterwards! Mind you I would think that the depth of heat treatment on a cam could support a 0.5mm clean up, provided that the shell thickness of the heat treated material isn't comparitively thin compared to the amount of material that is to be removed.
