So now that I have just finished getting all of the tooling necessary to make some real headway on this project I decided to start a thread showing the progress of this experiment. So if it's a disaster, you will all get to see it right here! The idea behind this project is to develop the 500/550 head to a point that will support much higher flow rates than can be achieved with the stock casting. The 500 and 550 head are the same and when big bore kits are installed in the 550, the head really becomes the bottleneck in the potential of the displacement. Great gains are to be had from conventional upgrades such as porting and cam timing, however there is quite a bit more to be tapped from one of these things and this project is my little attempt to see just what those gains are. The stock intake manifolds result in a rather long runner length, not ideal for a small high revving engine but my guess is that it was Hondas attempt to retain some useable torque for the smaller bikes. For high perfromance purposes this isn't as much of a concern so the idea here is to shorten up the runner length to be more optimized for the Megacycle 126-21 cam that will be used in this build. The other design goal is to straighten the intake runner resulting in greater flow and velocity, greatly improving cylinder filling after bottom dead center which will also help optimize the cam timing. This intake design is nothing new, all modern sportbikes use this technology and it has been around just about as long as internal combustion.
To begin I have taken a CB550 head and cut it open with a ban saw to get a cross sectional view of the ports so I can see what I can get away with. 30 degrees is as steep as this head will go. Modern bikes have steeper ports however they have far less angle between the valves which allows this but 30 degrees is a huge jump nonetheless. The new ports will also have to be moved over so that they are in line with bore centerline. This will require plugging the stock ports with aluminum slugs. Some welding will also have to be done to the inboard side walls of the ports as there will be a void there when the new straight ports are machined. Then aluminum blocks will be bolted to the old manifold surface and milled at the new 30 degree angle. Spigots will then be pressed into these to mount the carburetors. The carbs for the prototype are Keihin VE series in 32mm. 1.5mm oversize intake valves and 2mm oversize exhaust valves are currently under construction, pictures soon!
