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General TR SU food
- Thread starter HarryL
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Crankshaft
Jedi Trainee
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Personally, I use straight 30 wt motoroil.
Extra Virgin Olive Oil.......Sorry couldn't resist.:smile-new: Actually I've been using ATF as it seems to have quicker throttle response than motor oil but maybe it's just me.
TR3driver
Great Pumpkin - R.I.P
Offline
I did some experiments years ago with my previous TR3A, and decided that straight 20 weight gave the best throttle response. Any thinner than that produced a bit of a lean bog, while 30 or 40 weight was definitely too thick and made it harder to control the engine smoothly.
But straight 20 weight is hard to find these days, so when I got the current TR3 running, I used 20W50, which worked well enough. Almost no noticeable difference when I eventually found a quart of 20 weight and went back to that.
I actually built a crude "vacuum cleaner" from an old mason jar and a cheap venturi vacuum pump from HF, just to make it easier to try different goops without removing the domes. I also eventually learned that my domes have enough slop in the mounts that just R&Ring the dome can affect jet centering! Gently twisting the dome CCW while snugging down the screws seems to make it more repeatable. (I'm sure CW would work just as well.)
PS, no doubt it depends a lot on where you have the base mixture set. If it is a bit on the rich side, then the accelerator pump effect is less important. Ambient temperature will make a difference too, both because the carbs tend to go rich with hot air and because the oil thins out when it gets hot.
But straight 20 weight is hard to find these days, so when I got the current TR3 running, I used 20W50, which worked well enough. Almost no noticeable difference when I eventually found a quart of 20 weight and went back to that.
I actually built a crude "vacuum cleaner" from an old mason jar and a cheap venturi vacuum pump from HF, just to make it easier to try different goops without removing the domes. I also eventually learned that my domes have enough slop in the mounts that just R&Ring the dome can affect jet centering! Gently twisting the dome CCW while snugging down the screws seems to make it more repeatable. (I'm sure CW would work just as well.)
PS, no doubt it depends a lot on where you have the base mixture set. If it is a bit on the rich side, then the accelerator pump effect is less important. Ambient temperature will make a difference too, both because the carbs tend to go rich with hot air and because the oil thins out when it gets hot.
TR3driver
Great Pumpkin - R.I.P
Offline
Interesting idea. I'll try one tomorrow.
Geo Hahn
Yoda
Offline
On later cars I think there was a seal (or something) at the bottom that could leak -- but on the SUs I am familiar with there is no place for it to go. So why do some people say they need to keep refilling those?
I suspect it is because they are over-filling the reservoir and the excess gets pulled in (as an upper cylinder lube?). When they look again the level has gone down and they top it up and overfill once again.
I suspect it is because they are over-filling the reservoir and the excess gets pulled in (as an upper cylinder lube?). When they look again the level has gone down and they top it up and overfill once again.
TR3driver
Great Pumpkin - R.I.P
Offline
Depends on how full you fill them. The earlier TR3 manuals say to, in effect, overfill them slightly every 6000 miles. I believe this is so the excess can slowly run down the center shaft and lubricate where it runs against the dome. But the dampers still work fine with the oil level lower and then there is no place for the oil to go.
For SUs anyway. On most TR6 (and Stags etc) with the emission ZS carbs, there is an O-ring seal inside the dashpot that can leak and allow the oil level to drop.
For SUs anyway. On most TR6 (and Stags etc) with the emission ZS carbs, there is an O-ring seal inside the dashpot that can leak and allow the oil level to drop.
In Bob Shaller's More BS about TR's he says to get a flat piece of glass or mirror,lay some fine sandpaper on it ,place the dome on that and gently rub the dome on the sandpaper to level out any height inconsistences. That way the the dome will sit square. And make sure to tighten the screws evenly.
Vila
Jedi Hopeful
Offline
I use 3 IN ONE Motor Oil. I am not taking about your normal 3 In One multi-purpose oil.
This stuff is a 3 IN ONE product that comes in a blue / white / black can rather than the normal multi-purpose oil that comes in a red / white / black can and it an be found at most hardware stores or on Amazon.
It is SAE 20 weight and is advertised as being for 1/4 HP or larger electric motors.
It comes in the standard 3 IN ONE can with the nozzle that makes it easy to put in the dashpots.
Vila
1933 Chevrolet
1962 Triumph TR4
1984 BMW 633 CSi
TR3driver
Great Pumpkin - R.I.P
Offline
I've done that; but it doesn't address the dome being a loose fit on the body (and screws). I didn't try to measure it, but I'd guesstimate the slop at around .005", which was enough that the jet would drag or not drag. Might just be my carbs, of course, but they both seem about the same.In Bob Shaller's More BS about TR's he says to get a flat piece of glass or mirror,lay some fine sandpaper on it ,place the dome on that and gently rub the dome on the sandpaper to level out any height inconsistences. That way the the dome will sit square. And make sure to tighten the screws evenly.
