The details.
The Ace Billet GT head is precision machined by CNC from a billet of 6061-T6 aluminum.
All of the design is 100% Ace. There is nothing remaining from the original factory head design. We just have the same connection points for ancillary systems to attach.
First, we decided to change the valve angles to 20° each. The factory used 26.5° valve angles. Our more vertical valve angles give better flow effect into the cylinder, and all the modern high performance engines are using steeper valve angles like this. Some, like Ducati, use 12° valve angles. However, we must connect to the existing side-draft EFI intake location, so we were limited in how much angle change to use. This is the only head for Royal Enfield which features these advanced valve angles.
With the new valve angles, and larger inlet valve (1.8"),we designed a new combustion chamber of a more modern and compact type, also like the modern high performance 2 valve engines of today. We didn't choose 4-valve because of the added expense involved. Our 2-valve package services the power and rpm needs sufficiently for our goals. The new combustion chamber is 50cc, and shaped for faster and better burn characteristics, has provision for 2 spark plugs or single plug and manual decompressor.
The ports are all new, and are internally moved to suit the new valve angles, and provide best flow capacity. This required changing one head stud length to a longer one, making room for the intake port. Our ports make a match to the existing intake and exhaust tracts, so that matching is already accomplished for the user.
Our valve springs and rocker package follow previous Ace trends. We use beehive valve springs for improved harmonics and better valve control with less friction loss. All the hardware is modern racing stuff. We also use high ratio roller rockers in this package. Choice of 1.7:1 or 1.8:1 ratio. This increases lift to approximately .475"(12mm) -.500"(13mm) max lift, depending on rocker ratio and cams selected. There is room for valve lift up to 14mm in the valve gear, for competition applications.
We also enabled pushrod oiling system to feed the rockers and valves. The UCE hydraulic roller tappets are equipped with feed holes to supply oil up the pushrods into the rockers. Unfortunately, Royal Enfield did not make use of this feature, and instead used their usual type of rocker arm with a side oil feed. We retained the side oiling passages AND enabled pushrod oiling to our roller rockers, for added oiling to the top end. The side oil feed passages are terminated with spray jets which are interchangeable so that a user can select or adjust the amount of auxiliary oil spray into the rocker boxes. We can supply the necessary racing pushrods that are equipped for pushrod oiling, and are strong enough for our applications.
Because of the rocker type, some small modifications to the rocker covers are required for clearance. This requires some welding and grinding and polishing. We can do this for users who cannot do it themselves.