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There are individuals of rare taste and discernment who are wise enough to allow one of Borg-Warner's precision-engineered masterpieces to assist their M.G.'s forward motion. They avoid the tedious need to repeatedly stamp the left foot, wiggle that irritating little lever, and enjoy instant and massive torque multiplication at the mere twitch of a toe. This leaves them free to concentrate upon the vagaries of worn suspension and steering - which is after all what M.G. motoring is really about - these words are particularly for you!
Attached to the carburettor linkage you should find a second cable in addition to the throttle cable, unless time or ignorance has taken its toll. This in generally known as the kick-down cable, perhaps more properly as the down-shift valve cable. It hooks on (or should do) to the downshift and throttle valve cam assembly in the dark recesses of messrs. Borg-Warner's aforesaid masterpiece. Its adjustment at the carburettor will vary the manner in which the gearbox behaves e.g. in the gear change-up point.
When setting up the engine valve rocker clearances it may often be most convenient to remove various fittings from above the rocker cover in order to gain clear access to remove and refit the cover. If you have ever dislodged the new gasket and enjoyed clearing up after an oil leak all over the place, you will understand why! Thus the breather gear and cables are removed and laid aside, perhaps without much of a care.
If the inner cable of the down-shift valve cable is allowed to go slack and retract within the outer cable, it may well become detached from the downshift and throttle valve assembly, in which case you will proceed to remove the trans. sump (drain the oil first!) and become rapidly and intimately acquainted with the assembly in order to restore matters.
This would be quite unnecessary if your cable had its little "crimp" present and secured in the correct place at the carburettor end of the inner cable. This crimp is a small-bore piece of brass tube about one eighth of an inch long which is intended to be secured on the inner cable. When supplied loose on a new cable it can slide inside or right through the adjustment fitting and be either hidden from view or appear on the fitting's wrong side. The purpose of the crimp is that when secured on the inner cable in this position it prevents this cable from going too slack and detaching itself from the cam in the gearbox.
With the carbs set at normal idle, the "crimp" should be crimped in position just in contact with the outer cable abutment at the adjuster. In this position the inner cable must be at rest and not under tension - the inner can be gently pulled and the point of tension sensed. Fix the crimp at the abutment just before tension on the inner cable can be felt. Since distances vary this must be done individually for each car, which is why the crimp is supplied loose on a new cable. With the inner cable now secured properly, we may now consider what else might be wrong at the carburettor end of the cable.
Quite probably, the clevis pin which secures the inner cable to the throttle linkage, was lost years ago and has been replaced by a well-worn undersized nut and bolt. The backlash present will certainly affect gearbox behaviour. Fortunately, clevis pins are available from your local auto-transmission specialist (see Yellow Pages). The C part no. was CLZ 0309, superceeded by AUC 2381 (check for the MGB) but you will be lucky to find one at an M.G. spares outlet.
Finally in this trilogy of troubles we come to "The Case of the Missing Clip". This, my dear Watson, was originally fitted to secure the outer cable to the adjuster. The outer cable should sit inside a recess in the adjuster about half an inch deep, from which it can be quite easily dislodged accidentally, by vibration or by mis-fitting. This changes its effective length. Since the purpose of the adjuster is to vary the effective length of the outer cable and hereby alter the gearbox oil pressure and gear change points, the prospect of the outer cable not being properly seated in its recess is not one to be encouraged unless you prefer to drive without top gear!
These little clips probably dropped off most cars years ago, and I have never actually seen one. They have no part number and are not supplied with new cables. The vital clue is found in the C Workshop Manual section 08.B2 where a careless technical artist has given the game away-by showing what it should look like, together with the crimp and clevis pin for good measure. One can only wonder at the punishment for such a gross breach in security! Get a length of spring (piano) wire from a model shop (10 or 15 thou. 20p), dig out loose round-nosed pliers, and make one. Aren't automatic M.G.s fun?
Addendum to last month's article;
Condensers fail either open or short circuit, and you won't know which, so cut the distributor condenser wire before plugging in your pre-mounted spare, or it might not work. (But you had already sussed that out!).
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