Chain Tensioner Question
 

The PO of my 70 911T had the engine rebuilt in 1985 at Autothority in Fairfax, VA at a cost of over $6K. There has been a total of about 25K miles put on the car since then. The rebuild including upgrading to E specs (cam, pistons) but minus the MFI. Also, there is a notation that the chain tensioners were replaced and "chain guards" were installed. What are these and are they a substitiute for the oil-fed tensioner upgrade? Should I be worried about tensioner failure since there has been so little mileage put on the car since the rebuild?

Chain guards, are a small collar that is placed on the shaft of the tensioner, just in case the tensioner fails.
You should check the condition of your tensioner collar at least every 12K miles.

The PO of my 3.0L SC put the guards on my car. However, I upgraded it to the new oil pressure fed tensioners. Perhaps you can have that as a project when you feel comfortable working on the car. The parts cost about $400-500 and it takes about half a day. It is an upgrade that enhances your car in the eyes of porschephiles and gives you a sense of security. Checking the state of the collars is almost as difficult as changing to the oil pressure fed tensioners.