Wow, 3.89 sounds really tall for a little motor. Aren't you guys running
in the 8000 RPM region? I'm running a 3.9 on Peyote--was running 4.1 but I
was lifting before the end of the straight--more from nervousness than
real need. With a steel crank I suspect these TR3/4 motors can spin to
7500. I use 6500 as a limit. I miss the 4.1 driving out of corners, and
I'm in second more often than before, but it's good overall. Probably adds
three more shifts per lap at the two tracks I run most. That's probably at
least half a second I need to make up with better ratios.
-----Original Message-----
From: Aaron Johnson [mailto:fpspitfire37@msn.com]
Sent: Wednesday, September 03, 2003 1:23 PM
To: rocky@tri.net; zhbmacaw@worldnet.att.net; fot@autox.team.net
Subject: Re: changing spitfire gear sets
Tom,
All the information I have is that any crown wheel and pinion should fit
any
model of differential regardless of what it came from...even
GT6/Herald/Vitesse and Atlas Vans, so strange things are afoot at the
circle
K.
4.11 is standard fair for my car but next year may require a move back to
a
3.89 when more horsepower and rpm becomes available. I would agree that
the
4.55 is not really ideal for a 1300 or 1500 and I don't think too many
people are using 4.55's in SCCA right now with 1147's.
Aaron Johnson
#38 F-Prod Spit MKIV Oregon Region SCCA
http://www.geocities.com/spitracer9
>From: "Rocky Entriken" <rocky@tri.net>
>Reply-To: "Rocky Entriken" <rocky@tri.net>
>To: "Tom Britt" <zhbmacaw@worldnet.att.net>, <fot@autox.team.net>
>Subject: Re: changing spitfire gear sets
>Date: Wed, 3 Sep 2003 14:15:09 -0500
>
>I'm curious, Tom, what track are you racing at that the 4:55 is too
>low?
>
>I race MiDiv (Heartland Park, Hallett, Mid-America, Gateway, Memphis)
>and run a 4:55. The only place it seems to hurt is the Memphis
>straightaway (the full end-to-end dragstrip), but then I'm glad to have
>it for the run down the backside through the M's, etc.
>
>(I also autocross, so good for that too).
>
>Back when Mid-America Raceway (St. Louis, not Omaha) was in use, my
>brother raced my car and used the 4:55 there even though it, too, ran
>the straight the full length of the dragstrip and runout, because he
>gained more between 1 and 10 than he lost between 10 and 1. When we ran
>at Hutchinson, an airport circuit, that was the only track the 4:11
>paid dividends.
>
>Also, in what way does your intended replacement not match up? Do the
>bolt holes not match, or does it not fit in the case, or what?
>
>BTW -- '63 would be a Mk. I, not Mk. III. Mine's a '64 Mk. I. I'm not
>sure of the specs, but seems I recall the diff case got bigger in later
>models, or maybe that involved using a GT6 rear. Call Ted Schumacher at
>TS Imports and pick his brain. 800-543-6648. He's answered similar
>questions for me in the past.
>
>--Rocky Entriken
>
>----- Original Message -----
>From: "Tom Britt" <zhbmacaw@worldnet.att.net>
>To: <fot@autox.team.net>
>Sent: Wednesday, September 03, 2003 12:21 PM
>Subject: changing spitfire gear sets
>
>
> > Friends:
> >
> > I am attempting to change my 73 spitfire, rear end gear ratio
> > from
>the
> > stock 3:89 to a 4:11. I have a 4:11 ring and pinion from a 63 mark
> > III,
>was
> > told it would match up, but it doesn't. I am a low budget vintage
> > racer
>and
> > looking for advice to solve this problem.
> > Any help would be greatly appreciated.
> > I also have a 4:55 ring and pinion, to low a gear for our track,
>probably
>good
> > for autocrossers, if anyone interested.
> >
> > Tom Britt
> > Spitfire racer
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