Photos of 167 hp 2-Valve Guzzi

[Skeeve]

For some reason I though the Herron head was inherently (no pun) inefficient. Obviously not the case, otyher things (as you point out) being equal.

 

Not as such: Herron, after all, was researching how to design more efficient aeroplane engines when he came up with them. And Herron heads were used in a 1964? vintage NA F-1 [Cosworth?] engine to achieve something over 100bhp/ltr, iirc.

 

Moto Morini did pretty well with their 3&1/2 motor back in the 70s, so much so that it has become a cult bike. That was a Herron head design, too.

 

No, what's inefficient about a Herron head is when you try to lead in the air from the side & make it turn a 90deg corner at the valve. All the modern J-brand transverse I4 engines [and BMWs new K1200] have intakes that are long and straight and only a small angle off the intake valve axis. Can't do that on a Guzzi, since the heads are way out there in the breeze...

 

Coming from a "dirty sheet" redesign, by ditching the spine frame and turning the intake about 90 degrees toward the centerline of the bike & raising it a little, you could perch an airbox about where the fuel tank is now, and put the fuel cell over the tranny & in the frame [similar to what Buell has done w/ his bikes] and maybe realize an improvement in breathing (from a straighter shot at the cylinder) and more mass centralization. Heck, you could even put the oil reservoir for the shock in the airbox, for better cooling [it wouldn't have too much effect on the intake density, & might be worth while... ]

 

But at the end of the day, would it still be a Guzzi?

 

Ride on!

[mike wilson]

The big advantage of Herron heads is in the production engineering area. Multicylinder engines' heads need quite complex machining operations on all cylinders. If the machine has one head for all cylinders, it is easy to gang the mills/drills and whatever so that all cylinders are worked on at once. You can then cut all the intake machining at once, reset and cut all the exhaust. If you have one head per cylinder, that is two loads of setting up per cylinder, rather than per machine. If you have the parallel bores of the valves of a Herron head, you can do all the work in one pass. Properly designed, as the Guzzi ones seem to be, the disadvantages of the poor gas flow are reduced.