I have used Headquarters in the past and they make good power you just dont hear much about them on here.

 

It is theoretically possible to both bore an Evo and stroke it, to give 106/107ci, however early crankcases won't allow such a big bore and even later ones are not exactly robust. I first stroked mine to 89", then looked into boring it as well, but decided against it. An 80" Evo is actually aound 82", so the 85" kits you see are simply using close to max rebore size to give a little extra capacity, while boosting compression.

The greatest benefits can be gained by talking to the likes of HDF sponsor Hillside. They use modern cams and port designs not available in the heyday of the Evo and can probably port your heads, plus supply pistons and cam that will give a serious increase in performance. TCs will be toast! Give Scott a call.

 

An outfit called Branch Flowmetrics did a lot of research on Evo engines in the 1990's. They published a study that was compelling reading for anybody who owned an Evo. What they did was to add various components(carburetors, cams etc) one at a time and dyno the results. As the study developed, they found several packages of components that worked very well together. Their area of expertise was taking a stock head and completely filling it in with weld and reforming the head with bigger valves and better flow. I'm sorry, but I can't tell you much more about them, but if you could do a search, you might be able to locate them and find the book. Better yet, if you could find Branch Flowmetrics(they might still be in business), you could pick their brains. If you can't find the book(it's more like a pamphlet), let me know and maybe I can find my copy.

 

Thanks for telling me about Branch Flowmetrics. It looks like they're called Branch O'Keefe now. However I can't seem to find the research you speak of anywhere. I'm gonna keep looking but if you could find yours it would be a big help.

Thanks

 

They changed the head configuration from a "D" shape with a single squish shelf to a "bathtub" shape with two squish shelves. They also enlarged the valves & ports, & polished everything. I'm runnin' a set of Branch heads on the FXR. The reduced head volume raised compression while the squish shelves increased turbulence & fuel/air mix for better combustion.

If memory serves Branch sold/retired, but Flowmetrics is still around. Of course a lot of people did the "bathtub" head by the time Evo's went the way of the Dodo.........

 

OP,

You live in Jersey...do yourself a big favor, and check out the boys at Hillside Cycle in New York. They can turn your 80" Evo into a little fire breather without boring anything out.

You don't need big cubic inches in an Evo motor to make it kick some ***. The right cam, ported heads, carb, exhaust, ignition, and higher compression pistons can make a HUGE difference.

http://www.hillsidecycle.com/index.p...e-kits/80-evo/

 

The Evo is still alive and kicking!

Delopment of combustion chambers, ports, cams, etc hasn't stopped and I suspect Branch's current Evo heads perform even better today than when that report was written. Don't dwell too much on the past, just pick a current engine shop and see what they can do for you.

 

Actually, I agree with you, Evo's still live. I have an Evo style 96" Ultima motor sittin' on my floor that I'd like to have in my Road Glide. Just too old & lazy to actually do it.........

Amazon claims to have copies of the Branch Flowmetrics book, & Branch/O'Keefe is still open. A quick "Google" will find lots of info about them.