103711.1606@compuserve.com wrote:
> First, my compliments on an exellent page!
Thanks!
> I have a '74 TR6 that is plagued with carb problems. The Strombergs, being
> early emmision models, just won't cut it.
Kraig,
You'll note that I'm forwarding on this response to the
"triumphs" mailing list (triumphs@autox.team.net) in case others
want to add their perspectives as well.
I don't mean to rain on your plans, but if your car is having
carb problems, it is not because of chronic problems with
the Strombergs. It is indeed possible for a stock TR6 setup
to give thousands of miles of trouble-free service. I have
a '74 TR6 which I use as a daily summertime driver. It has
stock ignition and carburetion, and has provided me with
3800 miles of trouble-free service this year. I haven't
checked any ignition or carburetion settings since last fall.
My car is currently running rich, but as rich running is not
damaging to the engine (yes, it uses more gas, and is tough
on the environment) I haven't been able to make even the few
hours needed to adjust it properly. (Note that any carburetion
setup will require at least a few hours of adjustment for the
novice to set properly.)
> While attending a show / swap meet last weekend, it was suggested that I
> replace the Strombergs with a set of SUs. I picked up a set and talked to
> some enthusiasts about the necessary modifiactions to make the switch.
Did you find another TR6 owner with SUs on his/her car? I would
highly suggest doing so before embarking upon the switch. It may
not be as easy to do as it appears. Which type of SUs did you get,
by the way?
> Along with swapping the rubber spacers to remove the tilt from the bowls,
> I was to reverse the shaft to which the "butterflies" are attached. If I do
>that, I
> don't see how I can get the return springs and linkage to work.
> Do you have any information or suggestions on this type of mod?
The specific carbs on your car may indeed be worn beyond
repair. If the carbs are worn beyond repair, what is needed
is to switch to a decent set of carbs (whether newer
Strombergs or SUs, or Webers, or whatever...)
However, it is also the case that one should only attempt
to fiddle with the carburetors once the other operating
characteristics of the engine are in proper order.
Specifically, it is critical that the timing, spark, and
valves all be in proper adjustment, or making carburetion
changes will be fickle at best.
I would suggest first checking (or replacing) the spark
plugs, points, and condenser. Make sure that spark plug
and point gaps are correctly set. Verify that the coil
is providing adequate spark. Set the timing statically
according to the Bentley manual. With the engine cold,
adjust the valves, and ensure that the vacuum system is
connected properly. Once all of the above have been
done, and the car is still not running properly, it is
time to move on to the carburetors. (You may very well
have already performed all the above.) Note that you
will need to do all of the above first, whether you
keep the Strombergs or switch to the SUs.
When you do move on to the carbs, I would suggest at
least trying to figure out what is wrong with the
Strombergs first. It may very well be the case that the
problems you are experiencing have nothing to do with the
carburetors being worn out, but may be entirely unrelated,
and fixed by one of the above, or could be with the throttle
linkage or vacuum connections, or may be simply mis-adjusted
carbs.
Start with the basic stuff first. I am assuming that after
doing all the above that the car will at least run at some
semblance of idle. If not, you will need to attempt to
diagnose the problem without the car running, which gets
increasingly more difficult -- I would definitely suggest that
you get the car in a running state before trying to switch
carbs.
However, assuming that you have at least some semblance of
an idle, check to see that the throttle linkage is working
properly. I have encountered unusual problems at speed
which were the result of the linkage to one of the
carbs "slipping", giving different throttle openings in
the two carbs, and leading to odd misses at highway
speeds.
Remove the air filter, and use an air flow meter (such
as a Unisyn) to ensure that air flow through the two
carbs is balanced. Only after air flow is balanced should
one move on to fuel mixture settings.
If you are having real trouble balancing the air flow, and
if the carbs have not had any of the rubber components
replaced since new, it is likely that the diaphragms are
torn or cracked. To check this, remove the top covers, and
examine the diaphragms. If either of them look bad, buying
a pair of rebuild kits would be in order. (These could be
a problem even if you do succed in balancing the air flow,
so they are worth a look-see on any carbs of unknown history.)
It may be the case that you have worn carburetors which are
leaking air at various places, or there may be unconnected
(and unplugged) vacuum ports which are giving you an unduly
lean mixture. Vacuum ports connections can be easily checked
against a resource such as the Roadster Factory's parts and
assembly manual for correct connections. Air leaks can be
quickly tested for by spraying "starting fluid" around the
source of likely leaks. Are you getting no fuel in one
carb? Way too much fuel? It may be that the float levels
are misset in one (or both) of the carbs, or that the floats
have developed a pinhole and have filled with fuel. Resetting
float levels really requires removing the carbs from the car,
and would be a logical step as part of a rebuild, if you chose
to do that.
In summary, I would personally be very hesitant to replace the
carbs until after figuring out why the Strombergs weren't working
properly. At that point, you may be able to make some sort
of performance or reliability tradeoff to consider switching
the Strombergs to SUs. However, for ease of maintenance, and
being able to seek advice from others on possible fixes, you
may be better off sticking with the stock equipment, at least
until you are sufficiently familiar with the carbs to attempt to
make a better determination of a carburetor, and fiddle with
mixture/jet settings, as will surely be necessary with any
carb swap.
> Along with swapping the rubber spacers to remove the tilt from the bowls,
> I was to reverse the shaft to which the "butterflies" are attached. If I do
>that, I
> don't see how I can get the return springs and linkage to work.
> Do you have any information or suggestions on this type of mod?
Unfortunately, I can provide you with little information
as to how to perform the switch. If you do switch over, though,
let me know, and I'll take those horrible old Stromberg carburetors
off your hands, and even pay your shipping costs for ridding your
life of the hassle from the grimy hunks of pot metal.
--ken
'74 TR6 Daily Driver
VTR WWW Maintainer (http://www.vtr.org)
> 103711.1606@compuserve.com
> or
> mft@megahits.com
--
Kenneth B. Streeter | EMAIL: streeter@sanders.com
Sanders, PTP2-A001 |
PO Box 868 | Voice: (603) 885-9604
Nashua, NH 03061 | Fax: (603) 885-0631
|