This is the latest in the installation of the TR-6 motor in the frame. The cylinder and head are upstairs having the pistons fitted, valve guides installed and the decision being made whether bigger exhaust seats are needed for the considerably larger inconel valves. The delicate balancing act between how much power is needed versus how much can be produced before the head splits and/or the cylinders are knocked off the engine cases comes into play.
This bit of mental math usually causes Jim’s (the owner) eyes to roll back in his head. Keeping the engine heat manageable is part of the reason for the big exhaust valves. The effect of the big exhaust valves upon driveability (that is surprisingly important at Bonneville) is somewhat mitigated by the ability to change blower drive speed, and percentage of nitro. The engine heat buildup will also be more of a factor with the reversed head.
I will need to take a page from the Britten design book that made use of conduits and ducting to manage heat and feed air in the engine bay of the legendary V-Twin roadracer. If we have opportunity to do a billet head, the stability at elevated temperatures is so much better, the only heat consideration at that point will be the under-seat temperatures (aka “nut roaster”).
Some attention to the design issues of the early iron Hemis is needed to try and avoid certain flaws in the valve train longevity choices as the run-time of this combination will ultimately be much longer than a quarter mile, and while the valve train survived three miles at 8,000 rpm the first time, the pressure loading on the intake side and the heat loading on the exhaust side will be considerably higher, and survivability is a must.
The assembly of the first real bottom end will begin next week and we hope to have the frame out of the jig and fitting the wheels and forks in time to show it at the Slimey Crud Run Ocober 5 here in Madison. An intergrated oil tank/rear bulkhead along with the fuel, battery and varuous ancillary devices are yet to be done, so stay tuned as the work continues.