Hey guys I picked up an fxr awhile back and I love the bike. It's a 80" with flat top pistons, with branch heads, 520 cam and s&s carb. I recently changed out the pipe to a thunderheader. Bike runs good but like always I'm looking to get more out of it for cheap, if possible. A guy locally has a new 561 cam for sale. My question is should I swap this cam in and what power gains or differences could I expect? Would I need to change the springs and switch to adjustable pushrods to accommodate this cam? Should I look for a different cam?

 

My chart says its not a bolt in cam so you will need to contact S&S to find out what mods you need to do in order to make it work.

 

561 is the old school cam used for power, it is a 40 degree intake closing that will work well with flat tops and Branch heads, you should be at 9.5-1 compression. Yes the 561 needs springs but not alot of info out there on spring lifts on the Branch heads, it can be assumed that Branch heads have the ability for large cams because they where designed for power but it would be rolling the dice without knowing for sure.

If the 561 is a no brainer price say $50 bucks then sure but if you want a no guess power gain with the heads you have then a Woods W6H isn't a gamble but they require ajustable push tubes for lifter depth setting reasons but you need to do alot of internet surfing to get info on the heads, a company called Okeefe took over the Jerry Branch design and should be able to tell you what springs are in those heads.

 

I'd give Branch a call and see what they recommend. It sounds like a pretty good combo to me right now.

 

Branch turned it over to Okeefe, he isn't in the market any longer.

 

Thanks for info. I did not know that.

 

Thanks guys. I sent an email to branch with my motors details and asked what their thoughts were. It seems that if I'm going to have to re do the springs in the heads I might as well change the lifters and rockers to a full roller set up. And since I'm that far I might as well change to high compression pistons. And since I'm changing the pistons I might as well go to 85". So I've just took my cheap quick power increase to an almost full motor build. It's a sickness. Haha

 

85 is a con, its already 83" and 85 is just max oversize 1340 pistons, it leaves you nothing for a rebore later in life and adds no significant power.

 

Ah.... The Dreaded MAW's.... Responsible for more credit cards being denied than I can count...

Honestly, you should be able to get 90hp/85tq with just a bump in compression, street porting (your heads are probably already there), decent cam, tuned carb, aftermarket ignition, and a good flowing exhaust.

On an FXR, that would scare the crap out of this 63 year old...

 

That's good to know. I always wondered about how you could gain 5 cubic inches on an evo without boring the cases.