Bubbleback or Flatback?

[patsmith]

What is the difference between bubbleback and flatback powerheads and how do you tell?

 

[ezeke]

Re: Bubbleback or Flatback?

This is a copy of someone's engine photo showing the exhaust housing called a "flatback" between the cvylinder banks.

In the bubbleback, shown in the second photograph,the area is expanded outward for a larger cooling area and tuned exhaust.