Ping .boB

That's interesting; how do they accomplish that, I wonder? The stem to stud distance is different between ford and chevy small blocks - don't know about dodge. The same part number also fits an American Motors engine. Hmmmmm.

I dunno, I thought maybe a different pushrod pocket insert but that wouldn't change the stem to stud distance. Would you happen to know what those distances are?

No, couldn't tell you. I never took the time to measure them.

Perhaps it's so small you could design a rocker with and average distance that could work on all of them.

The difference between the Ford and Chevy's is the diameter of the valve spring. The Ford's are 1.63, while the Chevy's are 1.5. When the roller rockers are made, they are basically the same length, it's just that when they machine the tip for valve spring clearance, they don't need to take as much off for the chevy's. So the Chevy roller rocker won't work on a Ford, unless they are for a custom head for the chevy where they use the larger diameter valve spring, or for a ford that uses the smaller valve spring. Same holds true for the pedestal rockers. If you go to Summit or Jegs, and look up roller rockers and click on a couple examples, and look at the specs on each one, you'll see what I'm saying.

Also, I think some Chevy's use a 1.5 ratio for the intake, and 1.6 for the exhaust, or vise versa. Then there's the 3/8" & 7/16" screw in studs. If I was modding a motor and using a high lift cam, I would go with 7/16" screw in studs and guide plates to be on the safe side. The press in studs can be made to work, but that requires pulling the heads and sending them to a machine shop to have the studs pinned in. If your gonna pull the heads, you might as well spend the extra money and go with the screw in studs.

Gary