Henry,
See Page 22, "Auxillary Carb Return Spring" in Bob Schaller's "More BS About
TRs." He talks about that and has a fix for it. However, he says that "The
front carb leads the rear by a minute amount. This is likely to be
insignificant on the road but is noticable in racing."
By coincidence, Jack Brooks and I were just swapping emails about this very
subject -- this morning.
Sumner Weisman
62 TR3B
Date: Thu, 08 Apr 1999 16:57:04 -0400
From: Henry Frye <thefryes@iconn.net>
Subject: TR3 Carb Synchronization
Hi gang,
I have been happily tuning my TR3B carbs using the "rubber hose to the ear
and listen to the pitch of the hiss" method, until now. I won a gift
certificate from Terry's Jaguar Parts as door prize at the Connecticut
Triumph Register car show last year. Since I didn't need any Jaguar parts I
bought an Air Flow Meter. Same principle as a Unisyn, but there is a meter
instead of the floating balls.
Since the air cleaners came off today to get cleaned and oiled this was an
excellent opportunity to try the air flow meter. The carbs were pretty
close from last year. I loosened the coupler assembly, that accordion
pleated joint that connects the two carbs. I then dialed the carbs into
perfect unison, and tightened the coupler assembly.
Then I opened the throttle a crack and got the RPM's up to about 2200 on
the tach. I adjusted the Air Flow Meter for more air, and measured each
carb again. As I suspected, the carbs are now out of sync. The meter read
10 on the rear carb, and 14 on the front carb.
The accelerator linkage on a TR3 acts on the front of the front carb's
throttle shaft. There are two of these coupler joints between the carbs.
There is undoubtedly some slop in the couplers, and as a result, the carb
butterflys are in sync at idle, but not once you crack the throttle open.
The front carb is pulling more air.
It appears I can't get perfect synchronization at both idle and at speed.
Then, what is the optimum setting? Split the difference so both idle and at
speed are somewhat sacrificed? Or sacrifice the idle and go for perfect
synchronization at speed??? It would seem that being in sync at idle and
being farther out of sync with the throttle open is not the best way to set
it up. If this was a race car, I know that answer. ;-)
I think the accelerator linkage attachment point moved from the front of
the front carb to between the two carbs on the TR4 or thereabouts. This
would certainly be a major improvement...
- - - - - - - - - - - - - - - - - - - - - - - - - -
Henry Frye - thefryes@iconn.net - Connecticut, USA
Stag MkI Getting Sorted Out
TR3B Driver
TR250 X 3 The BIG Project - Will Be Worth the Wait
Homepage http://members.iconn.net/thefryes/
------------------------------
Date: Thu, 08 Apr 1999 14:08 -0800
From: "Ross Vincenti" <RVincenti@lbfc.com>
Subject: Re: TR3 Carb Synchronization
Henry wrote:
[snip]Then I opened the throttle a crack and got the RPM's up to about
2200 on the tach. I adjusted the Air Flow Meter for more air, and measured
each carb again. As I suspected, the carbs are now out of sync. The meter
read 10 on the rear carb, and 14 on the front carb.
The accelerator linkage on a TR3 acts on the front of the front carb's
throttle shaft. There are two of these coupler joints between the carbs.
There is undoubtedly some slop in the couplers, and as a result, the carb
butterflys are in sync at idle, but not once you crack the throttle open.
The front carb is pulling more air.
It appears I can't get perfect synchronization at both idle and at speed.
Then, what is the optimum setting? Split the difference so both idle and at
speed are somewhat sacrificed? Or sacrifice the idle and go for perfect
synchronization at speed??? It would seem that being in sync at idle and
being farther out of sync with the throttle open is not the best way to set
it up. If this was a race car, I know that answer. ;-)
================
For street driving, I'd go with the sync'd idle or split the
difference. You'll spend more time at stop lights and tooling along
at low revs where you will need the sync. My $.02 worth.
Ross Vincenti
Triumph-less for now
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