| Greg Reimer 7376 |
10-03-2015 07:24 PM |
Re: Valve springs 340 Stocker Engine
Quote:
Originally Posted by James L Miller
(Post 484086)
Sorry if I am ignorant on Stocker engine builds, but the spec I have for a 1969 340 calls for a .462" intake and .473" exhaust lift. Are people using a "square" lobe to loft the valvetrain off the lobe to get the .520" lift? I have an old Cam Dynamics 340 Stocker cam from the 1970s and it has a flattened nose on the lobes. I have some newer cams from Lunati and Bullet that have a more regular lobe appearance.
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The earlier cams had a more square nose profile like you describe because there was a maximum allowable duration rule in effect then.The valve started to open later,and it had to close sooner,so the lobe characteristics were more brutal. Parts breakage,valve bounce, bad stuff happened very frequently,especially on the go fast setups.The more recent stocker cams look more conventional because the ramp starts sooner,arrived at maximum lift about when it did, then closed later. Valve action was a bit smoother, and the engine would run at a higher rpm with out all that uncontrolled motion,Also,breathing started sooner and ceased later,making more power. DON'T EVEN THINK of using a square nose cam with a ceramic lifter. Get a set of Trend or Sherman tool steel lifters,fork out the bucks and do it right the first time. |