[Fot] TR7 Video and Carb Tuning

[Bill Babcock]

True, but maybe not useful. The main jet functions from about half throttle to
full throttle. If you modulate the throttle you'll see more need for fiddling
with all the other jets (idle jets, pump jets, etc.) so in a street car you'll
need to do more fiddling to get rid of stumbles and such at every throttle
setting. Race cars tend to be WFO so the only thing we really worry about is
the main and air corrector.

The air corrector tries to adjust the main circuit for differences in
differential pressure, which is proportional to RPM if everything else stays
the same--but it never does. You can actually tune upper and lower rpm ranges
properly with either air corrector or main. The air corrector serves to change
the mixture from what it normally would be when the throttle is suddenly
changed (ie. 1/2 to full).

As a thumb rule, Mike is right, but it's pretty hard to figure out that you're
lean at upper RPM unless you're tuning on a dyno with lots of instrumentation.
On track it generally takes some fiddling, but I've found getting the full
throttle mixture right by doing a plug chop and then paying attention to
throttle response from 1/2 to full puts me on the right track. If it sounds
flat (rich) when you change the throttle then go to a larger air corrector. If
it stumbles (lean) go to a smaller air corrector. Then do the full throttle
plug check again to correct the main jet.

On Apr 22, 2011, at 7:43 AM, Mike Munson wrote:

> To lean throughout the RPM range,go to a smaller main jet. To lean at upper
rpm
> range go to a larger air corrector jet.
>
> Mike
>
>
>
>
> ________________________________
> From: Craig Leinicke <craigl at leinickegroup.com>
> To: macdonaldp <macdonaldp at rogers.com>; Fot <fot at autox.team.net>
> Sent: Fri, April 22, 2011 8:17:48 AM
> Subject: Re: [Fot] TR7 Video and Carb Tuning
>
> Hello Paul,
> The looks and sounds awesome.
> Watching the video got me thinking about my TR7 weber carbs.
> Here is the current carb set up that I am running...
> Choke tubes -------- 30
> Aux. venturis ------- 4.5
> Main jets ------------  125
> Emulsion tubes ---  F9
> Air corr jets --------- 155
> Idle jets --------------- 55F8
> Pump jets ------------ 45
> Pump exh valve ---- 45
>
> My question to the group is... My car tends to run rich (full throttle land
> speed racing) and rich is better than lean.
> To lean the mixture which pieces should I change and which direction should
> I go... And how far?
> Thanks in advance for feedback... I'm racing mid-may at Maxton.
>
> Craig
> Flashback Racing
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Bill Babcock
billb at bnj.com
503.936.7660
www.bnj.com