Not sure why, but the TFS 170cc heads are ~300 bucks off: http://www.summitracing.com/parts/TFS-51400004 http://www.summitracing.com/parts/TFS-51400002
My guess is the release of the edelbrock E-street head. TFS needs a head to compete in that price range.
When demand for a product goes down or when they can't compete in the same price range then prices drop - at least until they are gone.
Why would you need new pistons for these heads? From the blurb it sounds like stock would work just fine...
it's because of the design of the combustion chamber these heads have. the valves are actually 'twisted', meaning set up in a different angle in a different position. the heads need pistons with differently positioned valve reliefs...
Nope! the twist is not an angled valve. the port is offset slightly from stock position and places the valve in a different spot on the head. they will work with factory pistons up to a certain amount of lift depending on how much of your deck has been ground off. i am running stock height flat top pistons with a block that has been only lightly milled. trick flow 1.6 roller rockers and an edelbrock performer cam. i have almost quarter inch valve clearance at the closest point so i could go WAY taller cam....