An interesting side note to the choice of oil for carb dampers is that
John Twist recommends 80/90 wt. gear oil for this purpose. I've had
good luck with 3 in 1 oil, which I started using when driving a Volvo
122S (HS6 carbs) for an everyday car.
Engine oil was too thick in the cold winter temperatures and ATF was too
thin in the summer. Since most of our carbs are old and have some wear
and are driven in the warm weather only, John's reasoning was that the
gear oil would work well.
Charlie
peter-thiel@sbcglobal.net wrote:
> Hi Rocky,
> Been reading the installments with interest. Good going on getting to
> where you're at with the TD. I trust you have some kind of manual to see
> pictures of the carburetor.
>
> The damper rods' pistons must be covered with oil, that's the important
> thing. If you overfill, the worst that will happen is a short period of
> smoke as the excess is sucked in and burned. I just use a squirt oil can
>and
> add to a little less than the top of the bore, and a few drops spill over.
> The thickness of the oil is important in the amount of damping of the
>piston
> assembly. Too thin an oil could result in hesitation. 10-40 will probably
>be
> OK, though different folks have different preferences, depending on the
>fine
> tuning of the car. Some use ATF (which is thinner) or straight 30 weight.
> Having oil (other than gear oil!!) in the dashpot is certainly better than
> none, the weight can be varied to suit.
>
> To remove the oil is simple. [Keep everything nice and clean.]
>* Unscrew and remove the top cap and damper rod/piston.
>* Unscrew and remove the retaining screws for the suction chamber body.
>* Pull the suction chamber straight up along the axis of the damper rod. A
> small amount of twisting back and forth of the chamber may help get it
> started. The main piston should stay in place on the carburetor. (If it
> comes with the chamber, no big deal, just gently pull it out by hand.)
>* Gently pull straight up on the carb piston until free, knowing that there
> is a "long" brass needle that must also come free. Do not bend, scratch or
> otherwise abuse the needle or John Twist will beat you with a stick. Dump
> out the old oil. Add the oil of choice.
>
> A couple of points:
>- Don't force anything! The British have an expression of "offering" one
> part to another during reassembly. If it doesn't go easily, back up and
>look
> at it closely and see what must be wrong before trying again.
>- A helpful book, out of print, but often available on eBay or Barnes and
> Noble used books is Tuning SU Carburetters, Speedsport Motorbooks, ISBN
> 85113-072-0. Any edition will do, but 3rd edition (1975) goes into later
>SUs
> with emission controls. There are other SU books out there, get one.
>
> Best luck, and be careful, it's a jungle out there!
>Pete Thiel
>'53 TD
>_______________________________________________
>mgcharlie@comcast.net
>
>Mg-t@autox.team.net
>http://autox.team.net/mailman/listinfo/mg-t
>
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