Welcome to our resource for MG Car Information.



TR parts and Triumph parts, TR bits, Triumph Car Spares and accessories are available for TR2, TR3, TR3A, TR4, TR4A, TR5, TR6, TR7, TR8, Spitfire and Stag and other TR models are available from British car spares and parts company LBCarCo.

Triumph TR6 - dashpot oil

I was wondering what oil to put in the dashpots of the ZS carbs on my 75 TR6. I bought the car last summer and the previous owner suggested and had used the same oil as the engine. I currently use 20-50 in the engine. If the oil is too heavy how do you remove and replace it.

think you'll get a variety of answers. I've always used straight 20W. Doesn't take much, just about everyone over fills them first few times. You want to fill so when you put damper back into slide you feel pressure with about 1/4 inch between top of filler and damper cap. Only way to completely empty is to unscrew 4 screws on cap of carb pull off carb top along with rubber diaphram and dump out oil or use a small diam hose and suction device.
Ian Kinaid

I have read so time ago that the best thing to use was Automatic trans fluid, it had the viscosity and weight as the proper oil that SU and Stromberg supplied.

I've using it as have had no problems.

You can get a plastic dropper from the local drug store/pharmacy and use it to suck up oil from the dash pots.

In general, the thicker the oil, the richer the air/gas mixture will be upon acceleration due to the way the Strombergs operate. 20W-50 is too viscous, IMHO, because you want that air valve to open up fairly quickly as you accelerate. Too viscous an oil will slow down the movement and make the rubber diaphragms stretch like balloons. I use Redline 10W-30, and have used Mobil 1 0W-30, but nothing's wrong with 20W or ATF, for that matter.
Brent B

The "right" oil is the one that suits your driving style. The range of suggested viscosities demonstrates this!
The purpose of the damper oil is to slow down the rise of the piston on acceleration, thereby enriching the mixture. If you want it a little bit richer, use a thicker oil.

Happy experimenting!

This brings up a question. If one of the carbs is running to rich and it looks like adjusting the needle does not do anything, is it a good idea to run a lighter oil in that carb??
Rick C
Rick Crawford

That's a definite "maybe", Rick. If you're running 20W-50 in a cold climate and are prone to accelerate a lot, it could be the problem. On the other hand the fuel level could be high in the carb float chamber, the air filters could be plugged, or the diaphragms could have failed, the damper air vent could be plugged, or the air valve is fouled and won't rise properly. Always function check the air valves to be sure they drop correctly after removing the thr carb top.
Brent B

Hey Guys - When they said to use the same oil as you use in the engine, that was right. Right for carbs in the 50's and 60's. In the summer, the engine oil was straight 30 weight. In the summer we used that in the dashpots for the carbs as well. In the winter, we used straight 10 oil in the engine as well as the carbs.

Today use 30 or 10W30 in the summer in the carbs. Otherwise use Automatic transmission fluid all year long.

Don Elliott, 1958 TR3A
Don Elliott

I have tried various weights. Ended up using straight 30 in my ZS and also in the SU's in my tr3a. Gave me the best overall performance. I do mostly warm weather driving
Mike Parkhill

This thread was discussed between 17/03/2003 and 18/03/2003

Triumph TR6 index