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This topic has probably been talked to death but here goes.Is it normal for the damper oil to go below the mark after a daily run? Seems I have to top it up frequently and yes I'm using the right level mark. I know some TR3 drivers that never bother checking the damper level! Also I've heard that using ATF gives a quicker acceleration response so I've been using it. How would thicker vs thinner oil affect carb performance when the weather gets colder? What is the actual purpose of the dampers anyway? Canada Karl
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SU Oil Dampers...Again
- Thread starter karls59tr
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vagt6
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Karl, FYI here's an excellent source of SU info: https://www.sucarb.co.uk/
I just posted a topic in the "Spridgets" forum on this very topic. My SU HS2s, which were rebuilt about 10,000 miles ago and seem to be in good shape (the car runs great, no problems), lose damper oil rapidly.
I use 3-in-1 oil and fill the dampers as indicated in all the manuals (i.e., "1/2 above the hollow piston tube"). It's gone within a week or 30-40 miles of driving.
I noted that I don't have "damper gaskets" so I ordered some from Moss. I wonder if the damper gaskets would cause such leakage?? Also, I'm going to start using the SU damper oil to see how that works.
Damper oil gremlins, just in time for Halloween?
What gives??? :confuse:
I just posted a topic in the "Spridgets" forum on this very topic. My SU HS2s, which were rebuilt about 10,000 miles ago and seem to be in good shape (the car runs great, no problems), lose damper oil rapidly.
I use 3-in-1 oil and fill the dampers as indicated in all the manuals (i.e., "1/2 above the hollow piston tube"). It's gone within a week or 30-40 miles of driving.
I noted that I don't have "damper gaskets" so I ordered some from Moss. I wonder if the damper gaskets would cause such leakage?? Also, I'm going to start using the SU damper oil to see how that works.
Damper oil gremlins, just in time for Halloween?
What gives??? :confuse:
TR3driver
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Kind of depends on which mark, but yes, the book says to overfill it somewhat and the level will drop from there. The excess oil runs down between the shaft & dome, to lubricate the sliding fit. As long as you can feel some resistance when inserting the damper, there is enough oil for proper engine operation.
The later ZS carbs have an O-ring that can leak oil; but on the TR3 SUs it is one piece and so very unlikely to leak.
The dampers basically give a richer mixture for acceleration, because that gives more power. It also helps accelerate the fuel through the jet (otherwise the mixture would go lean just when you want it to go rich). Very similar to an accelerator pump on a conventional carb. By keeping the piston from rising as fast as it would otherwise, the air velocity through the venturi is increased, which pulls more fuel through the jet.
Likely it varies depending on your engine's condition, state of tune, etc.; but what I found was that 20 weight motor oil worked best for me. ATF produced a definite "lean bog", while heavier oil made it harder to apply power smoothly without adding anything to performance. The racers use ATF or even nothing at all, but they also have their jets modified to run full rich all the time. For a street-driven car, it's better to have the cruise mixture a bit on the lean side (for less fuel consumption) and richen it only for acceleration (for better power). This is the stock setup. The owner's manual says "current engine oil", which would mean 40 weight for temps consistently over 20C, and 30 weight for temps between 0 and 20 (etc).
When the carbs are cold (which doesn't necessarily correspond to colder weather, since the carbs are warmed by engine heat), the effect is increased giving a little extra mixture boost for acceleration, kind of like a bit extra choke. But that is appropriate since the fuel also won't vaporize as well, so the engine actually runs better with a little extra fuel.
The later ZS carbs have an O-ring that can leak oil; but on the TR3 SUs it is one piece and so very unlikely to leak.
The dampers basically give a richer mixture for acceleration, because that gives more power. It also helps accelerate the fuel through the jet (otherwise the mixture would go lean just when you want it to go rich). Very similar to an accelerator pump on a conventional carb. By keeping the piston from rising as fast as it would otherwise, the air velocity through the venturi is increased, which pulls more fuel through the jet.
Likely it varies depending on your engine's condition, state of tune, etc.; but what I found was that 20 weight motor oil worked best for me. ATF produced a definite "lean bog", while heavier oil made it harder to apply power smoothly without adding anything to performance. The racers use ATF or even nothing at all, but they also have their jets modified to run full rich all the time. For a street-driven car, it's better to have the cruise mixture a bit on the lean side (for less fuel consumption) and richen it only for acceleration (for better power). This is the stock setup. The owner's manual says "current engine oil", which would mean 40 weight for temps consistently over 20C, and 30 weight for temps between 0 and 20 (etc).
When the carbs are cold (which doesn't necessarily correspond to colder weather, since the carbs are warmed by engine heat), the effect is increased giving a little extra mixture boost for acceleration, kind of like a bit extra choke. But that is appropriate since the fuel also won't vaporize as well, so the engine actually runs better with a little extra fuel.
V
vagt6
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Excellent, Randall.
I'll give some 20 weight motor oil a shot.
Thanks!
I'll give some 20 weight motor oil a shot.
Thanks!
TR3driver
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I still believe it's a good idea to do as the book says, and overfill slightly at service intervals; so the excess oil will seep down between the shaft & dome to lubricate the sliding fit. You don't want it getting sticky. I've also seen MMO get thick and gummy with age, especially in hot locations.
I made up a small "vacuum cleaner" from a cheap ($7 @ HF) air-powered vacuum pump, a mason jar & some tubing. Very convenient for sucking out the oil (for experimenting with different oils). You could probably accomplish the same thing with a Mity-Vac & it's brake bleeding attachment.
I made up a small "vacuum cleaner" from a cheap ($7 @ HF) air-powered vacuum pump, a mason jar & some tubing. Very convenient for sucking out the oil (for experimenting with different oils). You could probably accomplish the same thing with a Mity-Vac & it's brake bleeding attachment.
JohnnyMead
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I take the oil out by sticking a plastic hose in where the damper goes, hold the top of the hose shut and pull it out. It pulls the oil right out.
John
John