Thought I'd share my experience over the last few years in rebuilding the
SU carbs on my '63 TR-4. If you are one of those folks who can afford to
have your carbs rebuilt, you can just skip this - otherwise, you might find
this interesting.
I've owned the Tiggermobile (so-called by my wife who insists one needs a
"top made out of rubber and a bottom made out of springs" to be comfortable
riding in it) since 1992. It was a non-runner when I bought it - restored
on a budget from a pile of parts, the engine turned out to be too worn to
run properly, so the previous owner (a VDPO, by the way) abandoned the
project and sold it to me fairly cheaply. I spent the first several months
rebuilding the engine - new pistons and liners, valve job, etc. - and then
fired it up and tried to get it running. It started, but idled way too
high, and ran rough until warm.
Advice from a local LBC part seller led me to do two things. First, I
replaced the vacuum advance on the distributor, which was leaking. That
still didn't fix things, so I then examined the throttle shafts, which
turned out to be well worn. I shipped the carbs off to Apple Hydraulics
(who do great work), but since I was a poor unemployed historian living off
my wife's income, I just had them re-bush the shafts, not do a full rebuild.
After the carbs came back, I did a rebuild myself, using an NOS SU kit
that was sitting on the shelf of a local supplier. Combined with a
cleaning, this seemed to make the carbs much happier.
This helped a lot, and with the help of a Color-tune tool (gift from my
mother-in-law, no less) was able to get things running pretty well. Still
had some hesitation, though, so I replaced the needles and jets, and that
made it possible for me to actually drive the car on a regular basis. The
float valves had a tendency to jam, though, and make the carbs overflow, so
I invested in a fuel filter and some Gross Jets. Worked great - no
problems from the float valves after that.
All this took place over about 18 months, as I fixed one problem and then
fixed another. Since the car now ran reasonably well, I then turned to
fixing the other things the VDPO had done ( I hardly found one nut on the
car that was on tight...). I still had difficulty getting the engine to
idle below 1000 rpm, but since I had other fish to fry, I decided to make
do for the moment.
Flash forward to 1996. I got a job in Oregon, and move the car from sea
level to about 4,000 feet up (about 1200 meters for you metric folks).
This made things worse - the thinner air made for a poorly running car that
generated a lot of smoke from rich mixture. The car soon went in the
garage due to snow and ice, and I spent the spring and summer of 1997 out
of the country in Denmark, so it was not until the spring of this year that
I finally got around to fixing things.
I bought new needles more suited to high altitude ( the "lean mixture"
ones sold by Moss), new butterfly valve plates (the only part not replaced
in a previous rebuild), and new seals for the jets (the carbs were leaking
badly from the bottom). I also got new seals for the manifold- carb
connection. I installed all the parts, and the effect was dramatic - the
car ran like new. I barely need to use the choke to start it anymore, It
idles smoothly at 600 RPM, and it has more power and gets better mileage.
One important note on the jet seals. These were made of felt in the carb
rebuild kit I used before, and there was always a little bit of gas on the
bottom of the carbs. As a result, the Tiggermobile always smelled like a
refinery, and I had to install an exhaust fan in out garage to get the
fumes out. The new seals that I got from Moss are a rubber o-ring style.
They work far better, and I urge anyone who still has the felt rings to
replace them immediatly.
So, to summarize:
-Check for vacuum leaks, esp. throttle shafts, distributor advance
mechanism, and throttle butterflys
-New needles and jets (of the proper type for your altitude, if needed)
make a big difference
-O-ring seals are much better than felt
-Gross jets and fuel filter can solve your float bowl problems.
Hope it takes you less than six years to figure all this out - I'm
enjoying my rolling restoration, but at times I wish I had known a little
more earlier on.
Mark Clark
Klamath Falls, Oregon
1963 Triumph TR-4 "The Tiggermobile"
1979 Chevy LUV "Joe"
1991 Mazda Protege "Her Car"
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