[6pack] tr6 high idle continued - update

[Mark Hooper]

Having eliminated the simple, one must speculate it could be more exotic.


It almost sounds like there are two problems; with one of them possibly being 
something to do with valve adjustment. That can certainly affect intake 
vacuum/air flow.


Are you certain that all three carbs are the same version? I had to exchange 
a unit or two to get three identical parts for my triple setup. There were 
fairly significant differences over the years and I was told it was rather 
important to properly match things. 


Also the carb vacuum port, you pointed out, is no longer fed to the retard 
port on the distributor. Without that, my car idle is almost 500 rpm higher. 
That is with a CC XR700 ignition, not just the standard points.


Mark

1972 TR6 (with triple Strombergs)



-----Original Message-----
 From: Dave <dave at ranteer.com>
 To: 6pack at autox.team.net
 Date: Wed, 06 Feb 2013 11:16:08 -0500
 Subject: Re: [6pack] tr6 high idle continued - update


yesterday we did an interesting experiment.

 we swapped carbs 1 (front) and 3 (rear, next to scuttle).  obviously we
 couldn't connect the linkages, but everything else hooks up.

 after getting the car warmed up (had to manually push on two of the carbs
 accelerators to keep it going until then), I found that all three balanced
 very nicely and the car idled along happily at about 1100 to 1200 rpm (this
 car is rather modified so this is a good idle)

 there was no more issue about one carb piston being higher or registering
 differently on my flow meter.  all were nicely in sync at this point.

 putting the carbs back where they belonged the problem returned.  this
 problem was in evidence even with the accelerator linkage disconnected and
 the clips on the throttle linkages loose.  the rear carb pulls way more air
 than the other two, and the best I can do is about 2000 rpm idle





 -----Original Message-----
 From: Ed McGuirk
 Sent: Tuesday, February 05, 2013 9:41 PM
 To: 6pack at autox.team.net
 Subject: Re: [6pack] tr6 high idle continued

 The lifted piston in the rear carb strongly suggests that all the extra
 air is passing under that piston. You probably do not have a leak ( a
 leak would not raise a carb piston), you probably have an out of sync
 throttle plate or linkage. I think your next step should be to look
 closely at the rearmost throttle plate. How it sits at idle and how it
 moves with the other throttle plates and gas pedal. You probably will
 not be able to lift the piston and see the throttle plate with the
 engine running. You may need a flashlight and a mirror to see down the
 carb throat.

 ed

 On 2/4/2013 2:00 PM, 6pack-request at autox.team.net wrote:
 > Date: Sun, 3 Feb 2013 14:08:07 -0600
 > From: "Dave" <dave at ranteer.com>
 > To: "Triumph 6 Pack" <6pack at autox.team.net>
 > Subject: [6pack] tr6 high idle continued
 > Message-ID: <CA9F99F9AB1541E9A07E1E2D00EBBE34 at Datsun>
 > Content-Type: text/plain; charset="us-ascii"
 >
 > update on tr6 idling high.   triple carb, mild cam, etc
 >
 > Here's what we did this morning:
 >
 > 1.  found what looked like a vacuum port in the bottom of the middle carb
 > and
 > blocked it off.  it is likely once upon a time connected to the dizzy,
 > which
 > no longer has a vacuum connection.
 > 2.  blocked off all three vacuum ports on the top right of all three
 > carbs.
 > these were connected to the valve cover, brake booster, and vapor recovery
 > canister.
 > 3.  the car started, and idled very nicely at around 1200.  but then as it
 > warmed up, the idle increased back up to around 2500
 > 4.  checked the position of the pistons in the 3 carbs.  the front and
 > center
 > carb were more or less sitting at bottom, but the rear carb (by the
 > scuttle)
 > the piston was noticeably raised.  blocking off that carb completely
 > killed
 > the engine.  slowly blocking it off lowered the rpms, the more we blocked
 > it.