Randall:
The vacuum line I pulled off was the line attached to the "vacuum unit" on
the distributor. Frankly, I don't know if that is the advance or the
retard. My car is a 100% stock 76 TR6 and I don't know if its an advance or
a retard. My VB catalog for a 74 TR6 calls the line to the distributor a
retard line. The catalog has no name for the same line on a 76. Sorry no
manuals here at work.
According to my manuals, from a normal idle (which I had at that time),
pulling this off and plugging the line will cause your RPM to advance
(increase) up to about 1300, which mine did. According to my understanding
of all this, my car reacted normally.
I don't know if I have a TVS, since I don't know what a TVS is and can find
no mention of it in my only reference material here at work - the VB
catalog.
I am seriously beginning to suspect my temperature compensator(s). My
problems didn't appear until about an hour into the drive once everything
was good and warm.
Jack
-----Original Message-----
From: Randall [mailto:randallyoung@earthlink.net]
Sent: Thursday, August 12, 1999 12:23 PM
To: Radley, Jack
Subject: Re: Altitude and Carbs
Jack :
I'm not an expert on TR6, but some things are common to all car engines
: If you pulled a vacuum line off the distributor and the idle
decreased, you are very close to one of your problems. The vacuum
advance should not have vacuum at idle (and so disconnecting it
shouldn't make any difference to idle speed), and disconnecting the
vacuum retard (if you have one) should make the speed increase, not
decrease.
So : if it was the vacuum advance, you need to find out why it has
vacuum. It could be that your throttle plates are open too far,
uncovering the port in the carb; or that it is actually the retard line
connected to the advance. If your car has a TVS in the advance line,
the TVS may be failed or overheated. (Usually, the purpose of a TVS in
the advance line is to advance the spark at idle if the engine starts to
overheat.)
If it was the vacuum retard, then most likely the diaphragm has failed,
so plugging the line stopped a vacuum leak.
Randall
"Radley, Jack" wrote:
>
> Bud:
>
> This is a follow up to non-altitude comments you made regarding carbs.
>
> In my continuing carb adventure as soon as I felt I had my problems solved
> by adjusting the mixture, I too encountered very high idle speeds. When
> cruising at 2000 RPM, if I got off the gas and pushed the clutch in the
car
> stayed at 2000 RPM. It was like something was stuck open. So far I have
> done the following to my car:
>
> Rebuild by mechanic changing needles (B1AF), diaphragms, etc.
> Turned the idle trim screw all the way in.
> Attempted to use colortune - can't get a blue flame.
> Adjusted mixture to the point of getting very close to passing the
> lift the air valve test
> New plugs, rotor, and cap
> ATF in the dashpots
> Checked the vacuum by pulling hose off distributor and plugging -
> RPM went to about 1300
> At this point, my carbs are adjusted to about 1 to 1/2 a turn from
> full rich
>
> I am continually swapping one problem for another. I either get a rough
> engine pulling away from a start, or rough running between 1500 and 2500
> RPM, or fairly good running but a 2000 RPM idle. My problems seem to come
> up an hour or so into a drive once things have really warmed up under the
> hood. I have done nothing with the temperature compensator to this point.
>
> Any advice.
>
> -----Original Message-----
> From: Bud_Rolofson@nps.gov [mailto:Bud_Rolofson@nps.gov]
> Sent: Wednesday, August 11, 1999 5:32 PM
> To: triumphs@autox.team.net
> Subject: Altitude and Carbs
>
> In my attempts to retune the 6 since I returned home I discovered that I
had
> a
> vacuum leak on my front carb where the vacuum line connects for the vacuum
> retard. The plug failed so I think THAT was the cause of my
> increased(1800-2000 RPM) idle speed problem, which began my road to ruin.
> Since
> I didn't catch on that I had a vacuum leak I proceeded to "fix" the wrong
> thing
> creating another problem. If idle speed is off you of course back off the
> idle
> speed screws, right? Wrong, all that does is make the butterflies stick
> since
> it's the idle speed screw that keeps them from closing too tightly in the
> mixing
> chamber. So now I'd detuned it to the point where I HADN'T solved the
fast
> idle
> and HAD created another problem (sticking butterfly).
>
> I'm beginning to think the ZS carbs ARE marvelous in how forgiving they
are
> to
> people like me that just can't keep their mitts off them, since I royally
> messed
> them up and still made it 4500+ miles. I'm now a believer in the idea
that
> the
> constant depression principle compensates for the change in the air
density
> no
> matter what altitude you're at. I think that if your fuel/air mixture is
> correct at lower altitudes then it will still be correct at higher
altitudes
> and
> vice versa. I think Jim Altman's experience is a good example of this as
I
> believe he recently installed the B2Y (which is richer than a B1AF)
needle
> in
> his 69 TR6 because it was previously running way too lean with the
standard
> B1AF. Now if HE didn't have a problem with a properly tuned RICH needle
> than
> maybe nobody else will have a problem with a properly tuned standard
needle.
>
> However, like every other internal combustion engine you're going to lose
> some
> power at higher altitudes simply because you're not getting as much air
AND
> gas
> to combust.
>
> Leaner needles at higher altitudes ARE recommended by none other than the
> guys
> at Apple Hydraulics but I believe that is in order to retain the range of
> adjustment, not to CHANGE the fuel/air mixture (but I could be wrong
about
> this
> too). The standard needle is a B1AF which is what I use in my carbs. The
> next
> leaner (larger by 0.010) is a B1G needle and even leaner a B1CQ needle.
> When I
> replaced the jets a few months back I set them at a leaner depth (higher
in
> the
> carb body..as recommended by Apple) which is the counterpart to running a
> leaner
> needle since the opening on the jet is higher up the needle on the fatter
> part
> of the needle. The jet opening is also higher above the level of fuel in
> the
> float chamber so it takes a little more air to pull the fuel up and into
the
> mixing chamber which also makes it a little leaner.
>
> So my bottom line is the problem I encountered on the way to VTR with high
> idle
> speed was not fuel/air related and if I'd discovered the vacuum leak I
might
> have avoided doing something stupid (OK so that's debatable) like messing
> with
> the timing and carbs and I would have avoided starting this thread. My
> biggest
> mistake was having a preconceived idea that I was going to have to adjust
> for
> altitude (see I knew I should have started this thread 6 months ago), now
> I'm
> convinced that was wrong.
>
> I'm not just saying this so I get off the hook with Fred Thomas and Dave
> Massey
> either. Not that I thought for a second I could come up with a "turn per
> thousand feet" solution for every TR coming to Breckenridge in 2001.
Hell,
> it
> took me thousands of miles to figure out (with the help of many fellow
> listers)
> my own problem (or at least one of them). Now I know better.
>
> Bud
> 71TR6 CC57365
> 71TR6 CC65446
> 66TR4A CTC57806
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