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Re: rod length

To: riverside@Cedar-Rapids.net
Subject: Re: rod length
From: "Joe Boruch" <jaboruch@netzero.net>
Date: Wed, 15 Jun 2005 02:00:58 GMT
Below it is stated that deck height is set, but it is not.  A lot can be taken 
off of the deck, but the limiting factor is the sleeves.  Standard sleeves will 
tolerate making them storter to some extent, but not enough to make this worth 
the effort.  If 1/4 inch shorter sleeves were available (at a reasonable price) 
it would be worth the effort to have pistons made with a 1/4 inch shorter deck 
height and shorter push rods.  I looked into this a few years ago and took 1/4 
inch off a block, but with the sleeve issue I dropped further development.  
Joe(B)

-- "riverside" <riverside@cedar-rapids.net> wrote:
This topic used to cause me brain damage, but long ago,
i too made peace with it.

issue #1.  we are denied the advantage of building race motors from
a clean sheet of paper.  Our deck height is set.  New F1 engines have
rod/stroke ratios of well over 2:1.  Few street engines come that way.
V12 Jag is about 2.16.   259 Stude V8 is 2.11   Most are about 1.7 because
they were designed that way for a whole lot of reasons not related to HP
production.
the point is that we are severely limited.

#2   HRM is imho a poor source of race engine science.  I seem to remember
       a similar article about 5-6 years ago where they did get significant
       changes in HP with only rod and piston change.    above 5KRPM
       i doubt that there is much cam difference, but below 4K there would be
       alot of diff since the one advantage of a short rod is its ability to
get a
       stopped column of fluid moving better that the long rod.   Frankly, in
a
        race engine, I can't see this as a plus.


#3    The business with dwell time and rod angle advantage can be best
understood
        by those of us who are conceptually impaired  ( hell, it took me years
to
        understand how "caster made you faster")  by making paper dolls.
        use some stiff paper to make models of two setups.  Make one about
1.5:1
        and the other about 6:1.  an absurd example often best illustrates
the
        concept.  the change in dwell time will be noticeable.

#4     Is this "worth the time/money"?   Maybe we will find out, especially if
someone
         really goes whole hog with modern short compression distance pistons
so
         the longest rod possible gets squeezed in.
art d
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