Chicagoland MG Club
SU Carb Dashpot Oil
The purpose of the SU damper is to retard the rapid upward movement of the piston on the rapid throttle opening associated with acceleration. This delay in piston movement causes a momentary decrease in pressure at the throat, thus achieving a momentary increase in richness much the same as with an accelerator pump. The weight of the oil in the damper determines the amount of dampening. A lot of race mechanics use automatic transmission fluid for some misguided reason obscure to me. I think it is too light for normal use. SU publications recommend 20 weight, which I would follow.
Do not overfill the damper. The proper procedure is to fill "below the top of the hollow piston rod", not "below the top of the chamber neck". Overfilling just spills over into the suction chamber and makes a mess. One easy check is to remove the damper and then re-insert it. If you feel resistance before you reach the threads on the cap, you've put in enough oil.
and rectangular in shape originally designed to moisten labels and envelopes. It's called the Sterling Master Moistener and works just great!
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