[Stan Weiss]

Originally Posted by gtofreek

When it comes to using Ford rockers, there are times when they work, and times when they don't.

When I say longer valves, I'm not talking longer than the short valves in 6X heads. I mean longer compared to what came in a particular head from the factory. You need to keep in mind that when Pontiac uses a non adjustable valve train, the valve tips need to be at a certain height, regardless of head used, to be able to use the same pushrod in any engine[keeping in mind that 66 and older engines, and some 67 engines used shorter pushrods than the later 68 and up engines, including some 67 engines]. The valve length from the factory was determined by the depth of the combustion chamber. The deeper the chamber, the shorter the valve. When you install a longer valve than what came in a particular head, the valve tip becomes closer to the rocker stud than it was when stock valves were used. Now if you use a Pontiac rocker arm, the rollout pattern will be farther out on the stem tip, closer to the exhaust side. By using a SB Ford rocker in these applications, you can get the rollout pattern closer to center of the valve tip, where it should be. I find that when you increase the valve length .100" or more, the SB Ford rocker becomes a viable candidate. It's not a good choice for stock length valves. The 468 this thread was created for has valves that are .185" longer than the stock 670 valves, so the Ford rocker worked out very well here. I also find they work well in 389/421 heads when a .100" longer valve is used to get the spring installed height longer.

Paul,
Have you ever measured what the pivot length is for each? In other words what the difference in pivot length is.

Stan