I wouldn't start boring them out, thinning shafts etc is fine to do, but you
may have problems with the venturi effect if they are modified too much.
John Kipping
----- Original Message -----
From: "Aaron Johnson" <fpspitfire37@msn.com>
To: "fot" <fot@autox.team.net>
Sent: Saturday, January 31, 2004 5:14 PM
Subject: 1.5" Su's
> Well, I finally got my 1.5" SU set for the spitfire and I'm in the
> process of outfitting them to work on my 1296 race motor. The first
> thing I noticed is that the 1.5" SU's really aren't 1.5" they are 1.386
> on the out board side and 1.5" at the throttle plate. My thoughts are
> the first plan of attack should be to bore them out to 1.5" on the
> outboard side along with the thinning of the shafts etc... Any opinions
> on this, it was also suggested to maybe taper the bore on the way out to
> increase velocity through the carbs...
>
> What are the thoughts on blocking the balancing tube on the inlet
> manifold between the carbs, and any starting points for needles/jets
> would be helpful for a car with 13.5:1, cam is .560 total lift and 310
> duration...
>
> Also, I have a nice set of 1.25" su's for the 4 port spitfire head that
> will be for sale soon. I need to put new delrin bushings in them and
> they'll be useable as is. The manifold is ported and polished
>
> All the best
>
> Aaron Johnson
> #38 F Production Spitfire Mk4 Oregon Region SCCA
> http://www.geocities.com/spitracer9
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