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MG MGA - SU Carburators

Good evening gents,
I am tuning my two SU HS4 carburetors on my MGA, Can somebody please tell me exactly the quantity of oil needed in the dashpot piston unit and what type. (Viscosity)
Thanking you in advance
Mike PAIN

Mike

Just fill up the centre tube allowing a bit of space for the damper piston to fit in without overspill. Not critical though. Any overspill will quickly get absorbed and burnt in the engine.

I use a thin oil such as bicycle chain oil. Others on here go as high as 30 grade. I prefer the thinner oil for slightly quicker damping but others have their preferences as I am sure you will find out from following posts.

Steve
Steve Gyles

20 SAE by MG and SU, or many owners use fresh clean engine oil, other owners use a wide range of oils and viscosities.

If when you first lift the damper rod from the dashpot you feel suction on it then there is sufficient oil quantity in the dashpot.
Nigel Atkins

I always used ""3-in-one oil in my SU dashpots which seemed to work fine.
Like Nigel says, as long as you can feel some resistance when you lift the damper out of the dashpot, there is enough oil in there for the damper to work.

Its unusual to have the MGB HS4 carbs on the MGA Mike, the standard MGA carb is the H4.

Cheers
Colyn
Colyn Firth

I use a product specially made for SU's manufactured by Penrite Oils. It is available in UK and possibly US as well. Has the consistency of a 3-in-one. It is a light oil and works well.


From their website:
"Penrite Oil - More than just Engine OilsPenrite Oil - Proudly Australian Made & Family Owned Since 1926Where to buy Penrite Products?

SU DASHPOT OIL is a Mineral based oil containing anti-corrosion and anti-wear additives for the lubrication of pistons and dampers in SU and Stromberg carburettors".

Cheers, Barry.
Barry Gannon

Colyn,
FYI, I wrote an email to the WD40 company that owns 3 in One and their reply - ‘3-IN-ONE Multi-Purpose Oil' “is SAE 17, it is quite a fine oil.”

Whereas the ‘3-in-ONE Motor Oil’ (blue label) is equivalent to SAE 20.

I was checking out some of the oils some owners said they used (some used WD40 which must be way too thin), John Twist recommends “90 weight gear oil” which is in the 40-60 SAE crankcase engine oil range.




Nigel Atkins

I also use 3-in-1 in mine
Graham V

The correct amount is to fill to about 3/8" from the top of the damper tube. Standard viscosity of the oil is around 20W but depending on how your engine is built and tuned, you may require slightly higher or lower.
Steve Simmons

This thread was discussed between 12/06/2019 and 15/06/2019

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