Dan wrote:
> Yes, you are talking flow characteristics and it's relationship to VE
> and making enough power to spin the motor at high rates. But you can't
> even contemplate that flow rate at that engine speed if the crank,
> rods, and pistons can't support the rotation. You can put all the
> optimal lift and duration you want in order to make more power, but if
> the bottom end breaks at that speed it's meaningless.
>
> Certainly, it's possible to make high revving OHV systems, the NHRA has
> oodles of them . In the end, however, assuming enough power to turn
> the systems, the OHC version of a motor will out rev the the otherwise
> identical OHV version. It's simply because there is more mass and
> contact points in the valve train that absorb energy. This is one of
> the reason that small motors using OHC systems make alot of power
> relative to their size. Yes, there's head design and cam design and all
> that but in the end the OHC motor is pushing less around against fewer
> surfaces.
>
> .
> Dan
> 2003 Cobra convertible
> With some stuff and things
>
Hmmmmm...Ok, your talking about contact points in the valve train that
absorb energy. In the OHC motor, the crank has to turn 2 cams, vs. 1 cam
in the OHV motor. Also, you need to take into consideration that the
cam itself, in a OHC motor, has to open the valves, where the OHV
motor, the rocker arms open the valves, which act as a lever, and
require less effort. If the rod and main bearings are at proper
clearances, and in proper tune, an OHV motor will rev just as high as an
OHC motor. If you don't believe me, ask CobraJet, or any engine builder.
Back in the late 70's I built a .030 over 289 with forged pistons, stock
crank & rods, and a .535 lift .288 duration cam, and it redlined at 7500
rpms. It was still running when I sold the car it was in, and as far as
I know, is still running today.

Gary