It's possible that there is a difference in the piston spring tensions, the
front one being weaker than the rear one. Might pay to buy two new springs.
[mailto:email@example.com]On Behalf Of Cliff Hansen
Sent: Wednesday, 16 September 1998 8:16
Subject: Help with SUs on TR4A
OK I fancied myself a home-taught expert on these carbs,
but now I'm puzzled.
Where I'm at: Ignition working well and timing set.
Valves adjusted. Carbs have about 2000 miles on new throttle
shafts. The engine idles a little bumpy at 700, but runs smooth
at 1200 rpm or higher.
After balancing with a Unisyn and setting the mixture the old
way (lifting the piston and listening), I have noticed that the
front piston lifts noticeably more than the rear when maintaining
3000 rpm. The front is up about 1/2", the rear is about 1/8" lower.
My question: is there anything here to worry about? What does
it indicate about my engine's health? What adjustment is
needed (if any)?
Thansk for the help.
FWIW here's what I learned from my last questions:
1) Original floats are no longer available. Replacement floats are
all one piece plastic made by Rover; they do not have a copper arm
that you bend to adjust float level. Instead, you need to put copper
washers under the valve housing to set the right float level. I've
2) When you switch to heavier dashpot oil, you will effectively
richen your mixture. I switched from ATF to 10-30 about a week
ago. During the last week, I noticed the car was much harder to
keep running when cold, but accelerated more smoothly when
warm. I have some burbling when decelerating, indicating
unburned fuel in the exhaust. Also, plugs that were clean are
now a little sooty. I have found and will try the 3-1 blue can oil
(20 weight equivalent, made for electric motors.)
1966 TR-4A CTC 64615L