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Re: 302 flywheel weight??

To: "Derek White" <derekw@coppernet.zm>,
Subject: Re: 302 flywheel weight??
From: "Brian Moss" <BLMoss@Prodigy.net>
Date: Mon, 17 Sep 2001 11:28:07 -0500
Derek, I'll take a stab at it, and others can add and/or correct if I 
go astray.  

Flywheel weight runs from about 36 lbs for the stock, cast, 164 tooth 
flywheel to about 12 pounds for the aluminum 157 tooth racing 
versions.  You would feel a marked difference in the way your Tiger 
responds to throttle inputs between those two.  

Keep in mind also that there is about a 1 inch difference in diameter 
between the two, and that this plays a role as well.  Angular inertia 
is calculated as the weight times the square of the radius (or 
diameter -- I don't have the formula with me).  Regardless of whether 
I have the formula right, it boils down to the notion that reducing 
the diameter of the flywheel, even if it were the same weight, would 
result in less rotational intertia.  

One other thing -- factory bellhousings are made for a particular 
flywheel diameter.  Use a 157 tooth flywheel with a 164 tooth 
bellhousing, and your starter won't engage the flywheel.  
Aftermarket "blowproof" bellhousings usually have provisions to 
position the starter for both diameters.

So, my recommendation?  I'm basing this on my experience with a '65 
Mustang with a similar motor and about 300 lbs more curb weight than 
your Tiger (as the Tiger resto is still in progress).  The extra 
weight was probably more than offset by the wide-ratio Toploader and 
3.07 rear gears.

The best compromise for me was a 157 tooth billet steel version like 
those available from McLeod, FMS, and others.  The 24 lbs that it 
weighs, combined with the smaller diameter, give it good response 
without screwing up the idle too much (as Steve observed).  I have 
one for the Tiger, but I won't be able to tell you how it works out 
until next spring.

I stay away from the aluminum versions.  A misadjusted clutch or 
extra-rowdy driver can heat one up and warp it, resulting in serious 
clutch chatter.  I'm not a big enough fan of pulling motors out of 
Tigers to go that route.  They can also be too "snappy" for some 
people.

My final cautionary tale is that rotating mass and inertia are good 
things when it comes to balance and therefore engine life.  The big 
flywheel contributes by damping vibrations more effectively than 
smaller, lighter versions.  Tradeoffs, tradeoffs, tradeoffs.

Brian

--- Original Message ---
From: "Derek White" <derekw@coppernet.zm>
To: <SLaifman@SoCal.RR.com>, "Tiger List" <tigers@autox.team.net>
Subject: 302 flywheel weight??

>Hi Steve,
>
><snip>

>I understand all the flywheel issues you brought up. Surely someone 
has
>addressed this issue before? I am sure that the std 302 flywheel is 
designed
>to work well in heavy US cars and there should be someone who has 
figured
>out the best weight for a tiger given its weight, 1st gear and diff 
ratio.
>SOMEONE OUT THERE PLEASE HELP!!  I tried looking on tigersunited but 
the
>server is still down.
>
>cheers, derek

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