Car appreciation... the aesthetics, the engineering, etc

Cam designer has got involved with the 911 engine project, and has put the stock cams in his CMM.

Behold how weedy they are:

Inlet:-

Cam Lift = 10.500mm / 0.413”
Cam Duration at 0.102mm / 0.004” = 272°
Cam Duration at 0.508mm / 0.020” = 238°
Cam Duration at 1.000mm / 0.039” = 224°
Cam Duration at 1.270mm / 0.050” = 218°
Cam BCD = 35.000mm

Exhaust:-

Cam Lift = 9.982mm / 0.393”
Cam Duration at 0.102mm / 0.004” = 260°
Cam Duration at 0.508mm / 0.020” = 226°
Cam Duration at 1.000mm / 0.039” = 212°
Cam Duration at 1.270mm / 0.050” = 206°

Cam BCD = 35.000mm

There is a degree of consternation as to how those cams made 300 bhp, but that may mean that we'll get good results from a less extreme cam than we had thought.

This brings back into play the idea of re-grinding stock cams rather than using billet, and the cam designer also thinks that the stock, flat lifters can survive 8,200 rpm with the new tappet chests.

This would mean that we don't have to move to the rather lovely, DLC, domed GT3 lifters:

Which are, as mentioned, lovely - but with the billet cams already mentioned are probably 6k per engine that I'm quite glad we may be able to avoid.

Cam chap has come up with three different grinds of increasing lift and duration, topping out at a 12.5 lift intake and 11.5 exhaust. We'll grind a set of each and then dyno them back-to-back in each engine (one 3.7 and one 3.9) to get an understanding of the tradeoff between tractability and power - for e.g. the highest lift cam may lack the power to pull a greased stick from a pigs bottom until 4,000 rpm, at which point it starts a Saturn V impersonation. We shall see.

All of this means we need to get on with making the E60 M5 ITB's work nicely with the M96 heads and the GT3-RS centre section, whilst also getting an exhaust place to make some equal length manifolds to the correct specification. Exciting times.