Topic: Modifying the SOHC4 motor, is this possible??? Reverse facing head.

[crazypj]

This was done to death on the XS650 Garage about a year or so ago.
 As a design exercise its fun but for practical purposes (to get more power) pretty much a waste of time.
 You would be far better off making cold air intakes for stock air box
 The benefits of 'Ram Air' are less than negligible until you get over 100mph and no positive pressure is generated until 140+. (I think Kawasaki published numbers of about +2psi @180 mph, and that was an engine designed around a ram air system with fuel injection) Just work out how much air moves through the motor at redline with only 80% V.E. (CB550, around 20 liters per min @10,000rpm if my math is even close?)
 Plus, as previously mentioned, the exhaust side is around 250~300 degrees hotter than intake so the thermal gradient will be even higher with head reversed which will probably lead to blown head gaskets and distorted cylinders/heads (Cannondale almost went bankrupt trying to sort out problems with their engine)
 The stock Honda motor wasn't  high tech in the mid 70's so can be improved, without fuel injection and a powerful lot of electronics its going to be a nightmare (probably a nightmare anyway?)
 PJ

[jonbuoy]

+ how would you get any benefit by the time you have put on pod filters/airbox, unless you run velocity stacks? Would be really vulnerable to stone chips etc.  You could duct some air to the carb inlets but you would probably have to make sure the intake was shaped just right or you might find it makes it breathe worse rather than better.  Velocity stacks and bell mouths are shaped than way for a reason.   

[Soos]

thnx for all the insight!


had to have missed his motor was mostly billet.
Now that would solve a lot of problems!



Off to measure things...


l8r

[Big Jay]

Elmer Trett (RIP) did it.

Elmer trett did it with a bucket style motor where the cam lobes are symetrical. The profile of the rocker arm cam lobe would not work running backwards.

Also, I believe Elmer's motors had the cylinder block and head turned around.  There was no performance advantage in doing that. Elmer only did it for ease of supercharger adjustments, barrel valve tuning, etc.

Jay

[crazypj]

With dual OHC you can modify sprocket mounting and use asymmetric cams without any problems as they will open and close valves in 'normal' direction. With SOHC its sometimes possible to either modify mountings or bearing surface  and swap cam around 'end for end'
 The original V-4 Harley used stock cams with special drive for reversed motor, the 'new' version is getting custom cams (I got a little bit involved with it during design)
http://www.prostreetchoppersinc.com/article.easyriders.01.asp
PJ