OK Dave,
I think I understand what your saying. Had been following what old
Smokey Yunick once said "you can't have a rod to long". I might disagree
with him on this now. Our little 258 has a rod/stroke ratio of 2.4. The
piston seems to dwell at TDC so long that we have problems with valves
hitting (comming to close) to the piston with the cam we want to run. And we
don't have the valve gear to run 9,000 to 10,000 like the engine seems to
want.
I honestly believe there is another 100 HP in this motor. Hmmm, now how
much more can I bump the E/GCC record with an extra.....?
John Beckett, LSR #79
----- Original Message -----
From: "dahlgren" <dahlgren@uconect.net>
To: "Jane McMeekin" <jmcmeekin@worldnet.att.net>
Cc: <land-speed@autox.team.net>
Sent: Thursday, October 19, 2000 11:39 AM
Subject: Re: Bore/Stroke Ratio
> Personally i would not put in a stroke much shorter than the valve gear
> will rev..If the stroke allows for a 11,000 redline and the valve gear
> will only go to 8000 then you are giving up a ton of compression usually
> to keep the piston speed down to a point so low that you have very
> little inertia in the intake charge.. and a rod ratio that is so long
> you might never even see a torque peak.. ya gotta either have some
> leverage on the crank or enough rpm to make the small push on the piston
> happen very often...
> to me that rod you are running is mighty long...but I bet the side load
> on the walls is non-existant..
> Dahlgren
>
> Jane McMeekin wrote:
> >
> > Talking about a "favorite" Class "D" engine size makes me wonder if an
> > ideal bore/stroke ratio exists in terms of maximum power potential. Big
> > bore, big valve condition aside, should we expect a significant power
> > differential between a 4.25"x2.65" ratio and a 4"x3" size? Is the
> > primary reason for favoring the larger bore due to "better breathing" or
> > do piston speed, friction, and other variables enter into the equation?
> >
> > Incidentally the 3 Liter Buick has a 3.52x2.35 bore and stroke with 6"
> > rods. Our "fanny dyno" says its doing all right but maybe it could be
> > better.
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