Tech Tips: Spring 1989

Pilot Bushing Removal

The crankshaft pilot bushing, or spigot bearing for you anglophiles, is the bush that is pressed into a recess in the rear of the crankshaft, and which locates the transmission’s mainshaft. Although the factory workshop manual for the TR4 calls for its removal by threading the bush with a tap, screwing in a bolt and then pulling the bush out with an homemade puller, I have found a much simpler method. The principle of this short cut is to build up pressure behind the bush so that is just pops out.

First, fill up the space behind the bush with thick grease. This is easily done by inserting the tip of a grease gun into the recess and filling the space with grease, being careful to avoid air bubbles. Second, find a bolt that just fits into the bush. I found a cylinder head stud to work perfectly on my TR4. Third (see the above illustration), hit the stud smartly so that it is pushed further in to the bush. This will compress the grease and cause the bush to pop out. A method that not only takes less time than the shop manual procedure and it really works!

(This may indeed be an effective removal technique on a very thick-walled bush like the Triumph pilot shaft bush, but it is much less likely to be effective on the more typical thin-walled bush due to the significantly less end-surface area. —Ed.)

Ground Straps

Engine ground straps are essential, as they provide the ground connection for the starter motor, which typically draws 200-300 amperes. Should a ground strap be badly frayed, corroded, or otherwise unable to support this current, the starter motor will not be able to function efficiently. In extreme cases, the current will be carried by whatever else is providing a current path between the body of the car and the engine—usually the choke cable, which will become red hot. and may even burn through.

Carb Dashpots

Poor acceleration and “sputtering” during acceleration may be due to a low oil level in the carburetor dashpots. Automatic transmission fluid works well in some cars, but not in others. The old recommendation of “the same oil as used in the engine” is a good place to start. If this gives too lean a mixture on acceleration, try a slightly heavier oil; if too rich, then a lighter oil is indicated. Fill to within 1/4 inch of the top of the hollow air piston rod. Do not overfill!

By David Lenski