Power increase from stock '06 to '08 head?

8 replies to this topic
  • Zaj 243

Posted December 06, 2011 - 04:07 PM


Is there any benefit from upgrade a 06 head to a 08 head? I know the intake tract was straightened, what kind of changes in power could be expected from that? I know the '08's were up a couple HP from the '06, where did this extra power come from? Is one better than the other to use as a base to get a professional port job done? Any information anyone has on differences between these two would be appreciated, I am at a spot where I may need to purchase a new head and am looking for more mid-top performance vs. my stock ported '06 head. Thank you.

  • grayracer513

Posted December 06, 2011 - 04:19 PM


The extra power in the '08 came form a combination of port mods and cam timing. I think the '08 head is a better starting point by a small margin, but the authority on that would be Ron Hamp at RHC.

  • Zaj 243

Posted December 07, 2011 - 10:34 AM


Does anyone know the different camshaft specs for the years ranging from '06 to '09? I'm curious to see the timing of the lobe centers and compare them to the power characteristics of that model year.

  • grayracer513

Posted December 07, 2011 - 10:45 AM


Lobe centering on the '08-'09 cams is 100 degrees for both cams. The cam lobe profile is also different from earlier engines in '08. Prior to that, the original 5TA-00 cams in the '03-'05 were centered at about 107 as I recall. The same lobe profile was used through the '07 model, but the '06 used 105 degree centers, and the '07 slightly closer at 103.

I don't have a lift curve or duration figures for them.

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  • Zaj 243

Posted December 07, 2011 - 04:07 PM


I am running aftermarket cams right now, intake indexed at 108 degrees and exhaust is preset at 97.25 degrees. I feel the exhaust cam is limiting my peak HP and extention of my powercurve, general rule is higher degree btdc on exh cam higher peak hp and torque is carried. I am thinking about trying either the stock exhaust cam or a different aftermarket cam set at 103 degrees with slightly longer duration to help my bike pull longer to the rev limiter. The intake cam should be close, at least in the ballpark, closer than i feel the exhaust cam is to being the ideal setting for my application.

  • grayracer513

Posted December 07, 2011 - 04:50 PM


I am running aftermarket cams right now, intake indexed at 108 degrees and exhaust is preset at 97.25 degrees.

An interesting approach, I guess.

What's limiting your peak power is the longer centering of your intake cam. MXA experimented with the '08 quite a little bit, mixing cams between years. They liked the 100º '08 intake cam for high end power, but with the 105º '06 exhaust cam to widen the power curve out and bring more bottom end in. The intake has a much more pronounced effect on the power curve than the exhaust does.

You might like to read:


  • Zaj 243

Posted December 08, 2011 - 10:54 AM


I'm going to look into those MXA tests...sounds like some good stuff. I might ad this is a flattrack race bike, with a taper bored carb and pipe made for higher RPM racing than maybe what a stock engine/carb would be able to support. My head and porting is stock. The cams I am currently running are the stage 2 Hotcams, but I also have the stock '06 cams to play with. I agree with what you posted about the exhaust cam and what degree MXA liked, 103-105 seems like a more reasonable range than the 97 degrees the hotcam is set at. Do you think 108 degrees is still too high having a non stock intake setup? Web camshafts sells cams specifically for my application, but very high $$, that are set at 107 intake and 103 exhaust, if I were to run the stock exhaust cam or the stage 1 hotcam exhaust it would put my lobe centers close to that proven settup and give near idential lobe separation, similar lift numbers, only major difference would be their lobe profile. I will check out your link later gray, hard to get on the comp here at work!!

  • grayracer513

Posted December 08, 2011 - 01:29 PM


Without seeing the grind sheets for the cams you currently have, I can't say for certain, but the 108/97 offset you have between the intake and exhaust seems extreme, and unlikely to produce good results.

It should be noted that cams that are ground with longer durations tend to have wider lobe centers to avoid excesses of overlap, so you can't always compare on cam to another with a different grind by considering only the lobe split.

  • Zaj 243

Posted December 08, 2011 - 07:09 PM


I agree, extreme and I feel there is more to be gained. Sure, I could send my head out and drop 2g to get it CNC ported and custom matching cams, but I like to search and try different setups with low cost off the self options and try to get as much out of my parts available. That link you posted was great information, actually the info they state about lobe separation widths is opposite of what web camshafts says, and also aligns with what you have posted as good combinations with various years of OEM camshafts. I should have things pieced back together next week so I can degree and record exact measurements of the 4 camshafts and compare different combinations and see how things look. I wonder why hotcams would sell the stage 2 cams described as "excellent top end and overrev" with such wierd measurments.

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