performance cam

[molennick]

what is the highest degree duration camshaft available for a 240z? my friend says they go past 360, but i doubt this. lots of opinions wanted. thanks.

[Phred]

First, be aware that there are two methods of measuring duration.The first is total duration, where the starting, or opening point on the degree wheel is the exact point the lobe departs from the base circle. Concluding when the lobe reenters the base circle. These points are very hard to note on a degree wheel. But these are much bigger numbers than the standard checking points (usually .050, but not always), so the manufactures always advertise these numbers. The real world duration numbers will be the duration at the "checking height", (.050, or whatever the manufacture designates). So when comparing duration numbers, make sure they were checked at the same height to make a valid comparison.

For example:

Electramotive used to sell the trickest cam for the L28 GT2 engines. This cam was designed for Titanium valves, and made power to 9000 RPM, and produce around 300 HP. I can verify this because I built and dyno'ed these engines. Typically, the specs, checked @ .050 were as follows:

Int. open @ 25 btdc Exh. open 55 bbdc

Int. close @ 55 abdc Exh. close 25 atdc

Int. Dur. 260 degrees Exh. Dur. 260 degrees

Lobe centers 105 degrees

Lifts were kept down to about .590 for valve spring life, or for a one race shot like at the runoffs we could squeeze out another .025 lift by changing lifters and lash pads.

FWIW

Phred