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Re: Big Bore Kits

To: Richard Taylor <n196x@mindspring.com>, fot@autox.team.net
Subject: Re: Big Bore Kits
From: R John Lye <rjl6n@uva.pcmail.virginia.edu>
Date: Tue, 15 Jul 97 13:29:16 EDT
Hi all,
    Some random thoughts before getting back to work after
our trip to the Dallas sweatfest...

On Jul 15,  8:54am, Richard Taylor wrote:
> first thought is that the road to power is paved with cubic inches.

Tha certainly helps.

> 1.  Is there an optimum size?

That really depends on the answer to:  Optimum for what?  For
sheer horsepower, I'd guess that bigger is almost always better.
In fact, I've heard rumors that Phase One, out of Virginia Beach,
are working on a 3.0 liter kit for the TR-3/4 motor, but they
can't keep them together long enough to finish a race.  For
reliability, smaller is probably better, since there's more
metal to provide strength.  Of course, if the rules require
certain bore/stroke measurements, those will be optimal <grin>

> 2.  What are the biggest pitfalls?

You can find piston and liner kits which are so large that you
have to machine the block and lose soem strength, which can
lead to some very large expenses!

> 3.  Is the concept of lots more cc's the right one?

In general, subject to the caveats above.

> 4.  Is much (any) special machining necessary?

Depends.  If you stick with the 86 or 87 mm liners, there's no
special machining required.  Much larger than that and you'll probably
have to do some machining.

> 5.  What is the best source and cost?

I've been getting liners from Ken Gillanders at British Frame and
Engine and am quite happy with them.
 
> My ultimate goal is to build a strong, tourqy motor; not a super high
> compression fire breather. If 150 hp is somewhere around optimum for a TR-4
> motor, I will shoot for 125. For you real racers this may be some sort of
> perverted heresy, but for me, I will rely heavily on torque and reliabilty
> until (& if) my driving skills warrant a more aggressive approach.

I think that's probably a very good strategy.  The best bang for the
buck in performance improvements is *always* to improve the nut the
that holds the wheel.  After that, I'd suggest getting the suspension
to really work well - then work on that killer motor.
====================================================================

On Jul 15, 10:25am, Chip Bond wrote:

Buncha good stuff snipped...

> 5. And then there is the camshaft....John Lye,  what is the BFE grind you 
> have in your car? That may be a good one for this application.

As I recall its either a 300M106 or 308M106; I'd have to check the
invoice to be sure.  Its what Ken calls a "short track" cam; its 
working quite well for me.

> 125 HP is a resonable goal and will result in a very reliable engine with 
> minimal expense and maintenance.

I'd concur.  I ran a motor about like that in my autocross car for
about five years with excellent results and very little work.

best wishes,

John Lye

rjl6n@virginia.EDU
http://avery.med.virginia.edu/~rjl6n/homepage.htm

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