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Dash pot oil

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jordan k Jordan Kurtin
Toronto, ON, Canada   CAN
Is there a better oil to use in the SU carbs. Also how much oil do they take. New to Tr6 s and have never had to deal with this before. I see Moss sells a dashpot oil but it seams $7 for 125ml it got to be something special. Thanks Jordan

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barry s Avatar
barry s Silver Member Barry Stoll
Alexandria, VA, USA   USA
1972 MG MGB GT
1974 MG MGB
1976 Triumph TR6
1980 MG MGB
Their are a variety of opinions on acceptable oil in the pistons. The most common is 20W50 engine oil.

M. Pied Lourd Pied Lourd
ON, Canada   CAN
Hi Jordan,

Stock carbs on a TR6 are Zenith Stromberg (ZS). Has your car been converted to SU's?

Yes, you will get a lot of different opinions on what oil to use as pretty much everything from Engine Oil to Transmission Oil can be used (with different effects on the carbs).

I Use 3 in 1 oil that I think is about 20W.

I like the little container it comes in with the pull out telescopic spout...works great for adding oil to the dashpots. You can buy it at your local Canadian Tire.

Be sure and join the Toronto Triumph Club. We would love to see you come out with your TR6. www.torontotriumph.com

Cheers
Tush

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tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
Gosh, dashpot oil should be a sticky subject!

Why a "dashpot"? It's a damper, so slow the ascent of the piston as flow increases when you open the throttle.
Raising the piston pulls out the needle, to meter the flow of fuel.
An SU, or a Stromberg is a "Constant Velocity" carburettor, which is designed to deliver the right (Stoichiometric) air/fuel mixture, so how does it deliver a richer mixture when it is needed for acceleration?

The slowed piston narrows the throat of the carb, so the flow gets faster.
By Bernouille, the pressure at the throat goes down, so more fuel is sucked into the flow.
So it acts as an 'accelerator pump', to richen the mixture as it is needed.

The thicker the oil, the more the piston is slowed, the more pressure is reduced and the more fuel is sucked into the air flow. And vice versa.
So, if you want fuel economy, use a light oil - 3-in-1 for instance, is about SAE 20, ATF is 10. Triumph recommended engine oil, whihc is a LOT cheaper than what Moss sells! Or try something a bit thicker if you have a heavy right foot!

John

jordan k Jordan Kurtin
Toronto, ON, Canada   CAN
Thanks for the info. It all is good. jordan

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
The oil acts as a damper to slow the rise of a piston that allows more air into the engine. If this were not done, when you first step on the throttle, the engine would momentarily gulp air before gasoline could be drawn into the air flow.
Other types of carb use an acceleration pump to pump raw gas into the flow, to achieve the same thing.

The weigh (viscosity) of the oil used will effect how rich the Air/Fuel is in that second or so when you step on the gas. Heavy oil will make the A/F richer, lighter oil leaner.
The rule of thumb is: Whatever oil you put in the crankcase.

Wheel13 Mark W.
Los Angeles, CA, USA   USA
Hi All,

Follow-up question please. How do you know when to add oil? Mileage? And how much? Just a few drops?
Thanks!
Mark

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poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
You use the damper as a dipstick. When completely dry the 175 ZS carbs well holds 3.5ml
There should be a description or a 'dipstick' illustration in the Fuel System chapters in Haynes and Bentley.



Edited 2 time(s). Last edit at 2018-01-11 03:10 PM by poolboy.

Spectre Avatar
Spectre John Q
Millstone, NJ, USA   USA
Using the damper as a dipstick, add oil until you feel pressure when there is about 1/4" between the top of the body and the bottom of the threads. Add a few drops, test, repeat. If you put too much in, just insert the damper a few times and wipe off the excess. I always use motor oil. Good luck!

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glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, GA, USA   USA
My TR6 has SU carbs. I use 20 wt non-detergent oil in the dashpots. Works great. However, I have tried ATF, which is about 10 wt, and had difficulties accelerating properly. Interestingly, the ATF was highly recommended by a friend with a TR6 equipped with SUs who had great success with ATF. Different cars have different conditions.



Current: 1973 TR6 W/Overdrive

Previous:
1963 TR3B W/Overdrive
1962 TR3A
1961 TR3A
1960 TR3A
1960 TR3A

Wheel13 Mark W.
Los Angeles, CA, USA   USA
Thanks guys, appreciate it. Special nod to you Ken!

Sapphire Avatar
Sapphire Walt P
York, PA, USA   USA
In the 1970's, in my TR4, I always used the 3-in-1 oil.
At every gas fill up I would unscrew the dampers from the dash pots and check the level.
Usually, it would require about 2 drops of that thin grade oil in each carb.
That car went well over 100K miles, and the carbs never needed any work besides air balancing.

Triumph always recommended engine oil (20W/50).
Just pull up the dipstick and let 1 drop fall into each dash pot opening at each gas fill-up.

If your dash pots use too much oil, try adding a little Bars Leak Stop Leaks.



1972 CC80594U Sapphire Blue

glcaines Avatar
glcaines Silver Member Gary Caines
Hiawassee, GA, USA   USA
In reply to # 1507010 by Sapphire In the 1970's, in my TR4, I always used the 3-in-1 oil.
At every gas fill up I would unscrew the dampers from the dash pots and check the level.
Usually, it would require about 2 drops of that thin grade oil in each carb.
That car went well over 100K miles, and the carbs never needed any work besides air balancing.

Triumph always recommended engine oil (20W/50).
Just pull up the dipstick and let 1 drop fall into each dash pot opening at each gas fill-up.

If your dash pots use too much oil, try adding a little Bars Leak Stop Leaks.

I wouldn't recommend using dirty oil from the dipstick that contains metal particles. It would be much better to use clean oil IMHO.



Current: 1973 TR6 W/Overdrive

Previous:
1963 TR3B W/Overdrive
1962 TR3A
1961 TR3A
1960 TR3A
1960 TR3A

poolboy Avatar
poolboy Ken D
Sandy Hook, MS, USA   USA
When I first started rebuilding ZS carbs, I'd include some of my blend in a little bottle such as this:


Attachments:
Damper Oil 001.JPG    41.5 KB
Damper Oil 001.JPG

tkamd73 Avatar
tkamd73 Silver Member Tim Bradley
Menomonee Falls, WI, USA   USA
Hi Jordan, I have a TR6 with Strombergs and a MGB with the SUs. Over the years I've used Castrol 20W50, 3 in 1, which is 20W, ATF, and the stuff Moss sells. They all worked well, in fact could never tell the diff between any of them performance wise, but from a dispenser point of view, 3 in 1 is the best. Currently using ATF, only cause it's red. Have Brad Penn in the transmission and diff, cause it's green, and the engine has the brown Dino stuff. This way all my leaks are color coded, when I get a spot on the garage floor I know where it came from, and what I have to top off. None of my American, German, or Japanese cars, with way more miles on them, leak anything, no fun at all. Tim

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