In case anybody is interested in why we are using the rockers for our lift increase, we have several reasons, depending on the application.
Of course, there are two ways to increase valve lift, and we are very familiar with both types, and have used both methods successfully in the past. The 2 methods are increasing the lift at the cam lobe, and increasing the lift at the valve via the rocker. In both systems, the added lift will incur an increase in spring pressure(load), and also increase in accelerations(speeds) of the parts being lifted to a higher lift over the same periods of time.
First, in keeping with our general theme of easy installation of a performance kit on the top end of the engine, by using the rockers to increase lift, we keep the lift increase on the head, so the user is not required to enter the cam chest and deal with changing cams which some users might feel is too "complicated" for them to want to do. Even with experienced users, it is possible to get the installation wrong if they don't pay close enough attention. So, this simplifies the whole matter, especially for those users who have little experience in engine building. One of our goals is to have the easiest installation for the user.
Secondly, it allows the use of the stock cams which have the auto-decompressor built into the exhaust cam. We want to keep this function right where it is, so that people may have the factory-supplied protection of their sprag starter system, as the factory intended. We understand that this can also be done with a modified cam too, but it complicates manufacture.
Thirdly, it is typically less expensive to build rockers than it is to have custom cams ground, so we expect a cost benefit to keep the cost of the kit lower, or provide us extra "room" to include other features in the kit at a similar cost level.
Fourth, on a performance level, adding the lift ratio at the rockers allows the accelerations of all the parts on the cam/lifter/pushrod side of the valve train to operate at the same rates as they would in a stock engine over the entire rpm range. The only increase in accelerations of parts in this type of system comes at the end of the rocker arm on the valve tip side(and the valve and valve spring stack), which is increased in speed when providing the lift increase from the rocker. Since our Ace valve train is engineered with the lighter parts than stock, and has the advanced beehive spring system for keeping spring surge and harmonics under control, we easily control these moving parts on the valve side of the rocker. By keeping the accelerations/speeds of these heavy parts such as pushrods and lifters at the same speed as stock, this helps keep the inertia of these masses under control, leading to easier controllability of the valve train, and this is more likely to provide better stability and less deflection, resulting in more accurate translation of the cam profile to the valve.
With the lift increase at the cam lobe alone, all of the parts on the cam/lifter/pushrod side of the valve train are subjected to increased accelerations, also along with the parts on the valve/spring stack side. Not that this is necessarily "bad", but it is a fact regarding the comparisons between these two lift increasing methods.
Typical engineering practice in modern pushrod engines distributes the lift percentages by about 2/3 of the lift supplied by the cam lobe, and 1/3 supplied by the rocker ratio. You will find ratio rocker systems in the vast majority of all OEM or performance pushrod engines today. It is certainly not a rarity, or unusual in any respect.
So, we see it as a viable tool in our toolbox to use to achieve our goals.
Regarding using cams to do the lifting, we have no quarrel with that either, and we have used that method in the Iron Barrel Fireball package to very good effect. We had the cams ground by a cam manufacturer according to our specifications, limited it to a fairly modest increase, and observed the results over time, before attempting to increase lift any further. When we did make the move to higher lift, we then moved to using ratio rockers to augment the lift at the lobe. And our systems for that engine distribute the lift increases at approximately the 2/3 lobe and 1/3 rocker relationship which I mentioned earlier, for all the reasons I previously mentioned.
It's all just tools toward achieving an end. It's not that there are "camps" which say "lobe", and other "camps" that say "rocker". They all play together, and proper engineering uses these tools to make the end user happy with the outcome. "There's more than one way to skin a cat". You can use all lobe, or you can use all rocker, or your desired combination of both, and get good end results from your lift increase as long as the rest of the valve train is up to the task.
I like cams, and I like rockers too. They are both important parts of the valve train. Most of all, I like to get good results by using the right methods and practices to make people happy with the performance of their engines.