SB 318 Wanting to build for a 67 Dart GT

In order to find out the cc amount of the head, you will need a small amount of grease to seal up a small plexi-glass square to cover the entire chamber so you can fill it with a burret (SP?) that has cc marks to note how much liquid went into the chamber.

I searched Summit for this, in general page; http://www.summitracing.com/search/.../Part-Type/Cylinder-Head-CC-Kits/?Ns=Rank|Asc

Rocker ratio is thecam lobe lift multiplied by the ratio of the raocker to give enhanced lift at the valve.

So if a cam has a lobe lift of .333, at trhe valve with a 1.5 rocker is a math problem that looks like this;

.333 X 1.5 = .499 (.4995 actual) and a 1.6 rocker will equal .532 (.5328 actual)
Being able to see the difference in the rockers isn't so easy. Expriance would help, but the point of the contact of the pushrod to the adjuster is moved in slightly closer to the mounting point of the rocker on the shaft.

A higher ratio will not only give extra lift, but it will ever so slightly in a most meager way, increase the size (Duration) of the cam. The general 2* larger seems to be what everyone agree's apon. Who am I to argue?)
But the real treat comes in with the increased intencity of the cam.

Opening and closing the valves quicker is a key thing in making more power.
just do not forget that the increased lift almost allways requires new valve springs to handle the increased lift. This is valve control, the biggest issue in making power. Do not skimp.
There is also a limit to increased ratio of the rocker. You can push it to far. Beyond the liftersabilty to work, retainer to guide clearance and of course.... do they make it? (Custom rockers are way expensive!!!!)

The fish gave some real good cam choices since you have a limited gear ratio.