The stock one definitely seems to be a weak point for those of us who Rev the crap out of our engines.
How exactly is this modified? I thought the oil pressure pretty much auto engaged this to the proper tension.
We modify the spring pressure internally and yes you are mostly correct, under rpm where the engine is producing strong enough oil pressure the tension is usually fine with the OEM tensioner specs. However once oil pressure falls off, such as off throttle decel situations or possibly a high G corner (We have seen this on our time attack car at 1.6+Gs) chain tension can drop dramatically to the point where we have seen chains jump a tooth or 2.
Also when you add in stronger valve springs they create more tension on the chain as well and in extreme situations can collapse the tensioner a bit under very high rpm. We stiffen the spring loaded portion of the tensioner so that when/if oil pressure falls off significant chain slack cannot occur and lead to jumping timing teeth.
Also we have seen competitors go to a modified fixed style of tensioner which in my oipinion is not correct as well. It puts too much stress on the timing guides and can cause failures due to the design.
Hope that helps...
