06 vs. 07-08 CRF450R Cylinder Head

If I remember correctly, the ‘06 has larger valves. I think the 06 was the fastest crf450 of those years. I’d search and go back and read the mxa tests of the 06 &07. Should tell you what you want to know. 

I believe you would need to change your auto decompression system to use the 07/08 cam.

Honestly, I would recommend reaching out to Jim Haeseker of Haeseker racing engines (209) 267-9032. 
 

Gotcha.

For what it’s worth, When rebuilding my 05 Jim wanted to do a 07 head & cam, he felt the biggest benefit would be cleaner running and better power in low and mid. Turned out to require quite a few mods / extra parts to run the 07 stuff which he didn’t think the extra cost would be worth the benefits.

I rode a 2006 CRF450R back-to-back with my 2007 CRF450R ---> 2006 was waaay gnarlier in terms of power delivery / snappiness --- it felt a lot faster (like 10%+). It was too much for me in that moment because I was so used to the 2007 CRF450R ... which reminds me how much tailoring 450F power has received over the years from manufacturers (KTM especially, as my 2022 KTM 450 SX-F is absolutely docile compared to the 2006 CRF450R motor, yet makes more power).

My 3 cents is:
Be honest with yourself regarding what level of power & snappiness you're after + changing CRF counter sprockets to +1 to control power = EXTREMELY effective --- so I tended to go with more powerful motor setups that ran cleanest and then take the edge off the power by adding 1 tooth to the counter sprocket (and with a Rekluse, too).

Also - I am getting out of the business of creating finicky Frankenbikes. Soooooo much time spent pretending I am Factory Honda ... and it turns out, stock bikes are pretty damn good, but .... because you didn't ask, here are the mods I now do on every bike (because they are worth it & almost universally improvements):
(1) Rekluse RadiusCX clutches (or whatever is newest)
(2) Dirt Tricks sprockets
(3) DID ERVT X-Ring chains (I get 120+ hours out of these! I throw them away when they look too worn - but no performance issues)
(4) MotoSeat complete seats
(5) CoreMoto stainless steel brake lines (on bikes that come with rubber lines) paired with Maxima Racing brake fluid
(5) Ride Engineering V2 calipers are sweet on Japanese bikes (not already rocking them)
(6) Maxima full-synthetic engine oils --- "Extra" + "Pro Plus" + "530MX"
(7) FasstCo Flexx handlebars --- like a fork revalve (better than Twisted Engineering bars IMHO)
(8) Luxon Nexus bar mounts --- have tried MAKO360s (good, but harder to setup w/ pre-existing hardware)
(9) Precision Racing Parabolic steering stabilizer --- for mx, singletrack, etc. No downsides.
(10) FasstCo Impact pegs --- they really do reduce vibration through the feet/legs
(11) Vortex ECUs programmed by Twisted Development or XPR Racing --- "Believe the hype"

That ^^^ is called "going off the deep end."

Mic drop.

Peace out.

Those 2005-2008 CRF450Rs are truly legendary designs - enjoy that beast (as-is)! 🤣