> I could entirely seal the rear SU's mouth (where the piston is seen) with
> my
> hand and still feel no suction. However, the engine did run smoothly. The
> rear throttle butterfly is opening in concert with the front SU's
> butterfly.
> Strangely enough, it would take about 10 seconds of holding my hand in
> front
> of it's mouth (at 3000rpm) before it started to skip out or falter. There
> was no rpm tach so engine speed is just a guess.
> I believe both carbs are suppose to act exactly alike, right? There is
> strong suction at the front carb.
>
The carbs need to be synchronized so that each is pulling the same vacuum.
You can do this using a synchronizing tool, or you can do it by ear, using a
piece of hose and listening to the "hiss" at the entry to the carb. You
then adjust the throttle butterflies independently until the vacuum, or the
hiss, is the same for both carbs. You do this independent adjustment by
loosening the clamps on the throttle shafts.
> The needle or jet is not centered on the rear carb. and I've been
> forgetting to do this (since Doug Matthews pointed it out). Essentially
> it
> keeps this carb's piston from completely closing so it hangs on the jet
> with
> about 3/16" before it hits the bottom of it's fall. Could this account
> for
> the lack of this carb's vacuum?
You need to center the jet before you attempt to synchronize the carbs.
With the piston hanging up where you say it is, your mixture will probably
be too rich at idle. I think I described how to do this in a previous
e-mail to you, and it sounds like Dave has discussed this with you too.
As regards "running in", I prefer that the engine be run in under varying
loads, rather than under no or low load, for the same reasons as stated by
Randall.
Michael Marr
1960 TR3A
2000 Jag XK8
Naperville, IL
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