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The slower time may be the result of the crude Combat porting job that Dave Comeau discussed in his treatise on Norton heavy twin heads, also some reference to that in the thread on flow testing by Connoz in the Commando section.It is quite an interesting thread, shows the graphs for all sort of different Norton heads, both standard and with various porting jobs. Seems the long stroke Commando engine does not rev high enough to make use of a 32 mm port, especially one that is poorly shaped. The engine will make more power with a bit smaller port and correct shaping.This was also explained to me by Herb Becker , builder of Commando engines that have won at Daytona .Of the Combat heads, Dave Comeau states that by today's standards of porting , the heads are essentially "ruined"Glen
The slower time may be the result of the crude Combat porting job that Dave Comeau discussed in his treatise on Norton heavy twin heads, also some reference to that in the thread on flow testing by Connoz in the Commando section.
It is quite an interesting thread, shows the graphs for all sort of different Norton heads, both standard and with various porting jobs.
Seems the long stroke Commando engine does not rev high enough to make use of a 32 mm port, especially one that is poorly shaped. The engine will make more power with a bit smaller port and correct shaping.
This was also explained to me by Herb Becker , builder of Commando engines that have won at Daytona .
Of the Combat heads, Dave Comeau states that by today's standards of porting , the heads are essentially "ruined"
Glen
