[Shotimes] (OT) Marauder

[David P]

Not three cams profiles per cylinder. Three profiles per cylinder spacing. The
cylinders banks are offset from each other, so, looking at the total length
dedicated to one cylinder, you have to profile 1.5 cylinders (1 cylinder plus
1/2 the cylinder from the opposite bank).

I was wrong, though, as I was only thinking about the cylinders at the end of
the block. This would only work on a V3! (or less) You actually will have four
different profiles per cylinder spacing on a single-cam OHV setup (intake and
exhaust of the cylinder that falls in the measured length, and the intake of
one cylinder and exhaust of another cylinder on the opposite bank). You can
v-rocker the intake and exhaust to provide only four cams instead of eight.
Not a problem with large cylinder bore, but as motors get smaller, the cam
lobe width has to decrease and the available length on the cam decreases. A
decrease in the width of the cam lobe requires a reduction in the spring rate
of the valve, which requires a lightening of the valve, or durability of the
cam lobe becomes an issue. There a definite alternatives like titanium and
beryllium alloys, but cost can rise considerably. I am thinking they need to
find a way to coat carbon fibre with stainless  ; )

The drawbacks of a little extra valvetrain mass is higher power consumption
and reduced rpm limit (unless money is no hindrance).


David P

95MTX



~
----- Original Message -----
From: <BJamesjr@aol.com>
To: <shotimes@autox.team.net>
Sent: Monday, November 04, 2002 17:34
Subject: Re: [Shotimes] (OT) Marauder


> > A 4V OHV motor has to operate three separate cam
> > profiles per cylinder spacing vs SOHC operating only two.
> > The cam gets a bit more crowded.
>
> 3 cam profiles per cylinder?  On the surface you would think 2 valves- 2 cam
lobes, 4 valves- 4 cam lobes.  However since OHV engines use rocker arms I
would think a Y-shaped rocker arm could easily operate 2 valves with one
pushrod.  An enterprising person could have built a 4-valve head for a V8
chevy long ago (may have even been done for all I know).  The only drawback
would be a little more valvetrain mass, but this would be counteracted by 2
springs per cylinder instead of 1.
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