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  #1  
Old 11th May 2018
VinceB VinceB is offline
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Default Heads Or Cams???

I'm not racing my bike but I don't know what other area to ask. I have an 03 883 XLH. I'm trying to figure out from a performance standpoint what my next move is. Cams or Heads? Here's the current setup
883 bored to 1207 with S&S 10:1 pistons

Stock heads and cams

Stock Carb with S&S Stealth air cleaner

2" diameter drag pipes

Dynatek 2000i ignition

What next?
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  #2  
Old 11th May 2018
jcro61 jcro61 is offline
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Default

Quote:
Originally Posted by VinceB View Post
I'm not racing my bike but I don't know what other area to ask. I have an 03 883 XLH. I'm trying to figure out from a performance standpoint what my next move is. Cams or Heads? Here's the current setup

883 bored to 1207 with S&S 10:1 pistons



Stock heads and cams



Stock Carb with S&S Stealth air cleaner



2" diameter drag pipes



Dynatek 2000i ignition



What next?


I’d leave it as is

OR

Get the heads done and get the appropriate matching pistons AND cams.

The heads you have are dead before the stock cams would normally peak on a 1200 so putting bigger cams now won’t do much.


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  #3  
Old 11th May 2018
VinceB VinceB is offline
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Default

I tend to agree with that. I need to save some more money and do the second suggestion. It runs pretty well now but I'm interested in taking it to the next level when I can.
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Old 11th May 2018
jcro61 jcro61 is offline
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Originally Posted by VinceB View Post
I tend to agree with that. I need to save some more money and do the second suggestion. It runs pretty well now but I'm interested in taking it to the next level when I can.


Save up and send your current heads to Hammer Performance for the Smash port job and matching 1275 30 degree pistons with some 560 cams. The bike will screw. Proven combo that works every time.


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  #5  
Old 11th May 2018
mac93 mac93 is offline
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^^^ Agreed, it all works together. I’d leave and put a better exhaust on it, 2 inch drag pipes are not helping you at all. Talk to the Hammer guys or your builder on the best way to move forward.
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  #6  
Old 11th May 2018
VinceB VinceB is offline
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Default

I am the builder lol. We don't have anyone in town with a shop that does performance stuff anymore.
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  #7  
Old 11th May 2018
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aswracing aswracing is offline
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We get asked this basic question literally every day, usually multiple times a day. Guys do a basic conversion and they're thrilled with it, but after awhile they get used to the power and want more and they ask us how to get there. I wish I had a good answer for them, but without changing the pistons, there just isn't a good answer.

The complete reason behind that is kind of long and obscure and gets into a bunch of detail about how the heads and cams and pistons play together. The short version is that you can't put big valves into the heads, along with much overlap into the cams, without making the chambers bigger. You just physically can't do it without creating issues with valve-to-valve and valve-to-piston clearance. And bigger valves along with more overlap is exactly what the motor needs to make more power.

The issue is that making the chambers bigger drops the compression. Meanwhile, your new cams probably require more compression, not less. And you can't get your lost compression back with decking. Decking a head that far causes a whole new set of issues. You have to change the pistons.

At the end of the day, you have to think of piston and cams and heads as a matched set. You can't move any of those things very far without bringing the other two along. They're matched in numerous ways. Your reverse dome conversion pistons are well matched to the stock 883 heads and cams. They're not well matched to high overlap cams and big valve heads.

Doing a hop-up project incrementally over time is tough. You end up either buying some parts twice, or you compromise your result, or you push clearances much tighter than you should.

You can do a mild hop-up without changing the pistons, don't get me wrong. But we hate having disappointed customers, so we try to avoid that. Generally speaking that path leads to disappointment.

Not the answer I want to give, believe me. If I could bend the laws of physics and solve this problem, we could really help sales.
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