On Sun, 4 Jan 1998 18:49:36 +0000 "Scott Gardner"
<gardner7@pilot.infi.net> writes:
>> I agree Trevor (Honest I do agree with Trevor)
>> Every manual, handbook, or lubrication chart I've seen calls for
>the
>> same oil in the dashpots as used in the crankcase.
>> At the risk of sounding like some kind of purist kook, why should
>I
>> argue with the guys that put the thing together.
>>
>Rick,
> So, does that mean that the SU carb oil in the catalogs is
>just
>20W-50 motor oil? After all, they ARE the people that made the
>things.
>Scott
If you'll check with several different automotive applications for SU's
you'll find that in the majority of cases, the AUTOMOBILE manufacturers
recommended using the same oil in the dashpots as in the crankcase.
BUT, the crankcase recommendations vary with the manufacturer and with
operating conditions (ie ambient temp).
Does that mean the "genuine" SU carb oil magically changes its viscosity
as the application and temperature varied.
Yes Skinners Union made the carbys, to the basic specs of the car
builder.
They also make the needles, but you don't see one needle being sold as
the "genuine" SU needle as a one size fits all.
The viscosity of the oil in the dashpot is one of the tuning devices
on an SU. Heavier oil gives more "pump action". What works on one
application in one set of conditions, may very well not work in the next.
I've tried the "genuine" stuff, and frankly on both my cars they
developed a flat spot or hesitation when I jumped on the throttle. Going
back to a heavier oil in the dashpots cured the problem. Were I in a
climate where the outside air temp was in the 10's during the day, I may
find that they worked better with a thin oil.
The point is, with all the variables in tune of our cars, there isn't a
simple answer to the dashpot oil question, only a recommended starting
point.
Rick Morrison
72 MGBGT
74 Midget
Rick Morrison
72 MGBGT
74 Midget
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