do chains really stretch?

The tensioners looked good to me when Shady dell introduced them to me with a roll master. 14 pulls on a dyno and the tensioner was at its almost at its limit. They bought me every thing new when the motor left go. HTA machine would not use the chain or tensioner they bought. He ordered a custom length true roller chain. The tensioner that you are all describing was not design for a roller. A tight roller will wear real fast. a properly installed correct length true roller chain usually does not get alot of slack after use. I will be pulling my motor apart shortly to install a billet cover. We will see how loose the chain is . High seat pressure and sees 9000. I will take some pics when its apart.