Join Date: Mar 2003
Location: Kansas City
Motorcycle: RIP El Toro. Long live new bike BIG FOXIE! Ex KWS AMA 08 GSXR1000
Re: more power for less
I'd GUESS about 5 to 10 hp putting the K7/K8 head. From what I've heard, the K7 motor is worth about 10 hp over the K3/K4 motor, with the same mods
Most of that power is in the cylinder head setup (and with that I'm including what supports it - the bigger throttlebodies - 44 v 42mm, exhaust, etc). Of course, the big windage ports on the K7 are probably worth a few HP... they are there for a reason... and putting that head on a K1/K2 lower end will mean you dont have the crankcase windage holes like you would if you ran a full K7 setup.
But, are you planning on trying to keep all the K1/K2 parts except for the cylinder head?? I'm not sure how to read what you wrote. I ask because the K7 requires matching (K7) throttlebodies, which means a different ECU. Also, the K7 uses a different exhaust, which I believe is due to the different exhaust port dimensions (size and/or spacing). I can't remember whether people have been able to "bolt up" an earlier (k1-k6) exhaust to the K7 head, whether it physically fits or not, but either way, the K7 is SUPPOSED to have a matching exhaust (ie, for a K7). Even if the earlier one bolted up I dont think you'd get the power out of it that you should
Also, if you swap ECU's you'll need to swap the ignition rotor, the pickups are different for the K1/K2 v K3-K8 (different number of points, due I believe to the change in the number of bits of the processor - 32bit v 16bit)
And if you go with a K7 exhaust, I dont know if it will work with the earlier oil pan. The K7 went to a deep rectangular sump on one side vs the earlier bikes that used an inverted pyramid shape. And if you swapped oil pans to fit, you'd need to swap out the oil pickup at least....
The K1/K2 cams will NOT work with the K7 head, not without modification. The pin on the cams for the camshaft position sensor is repositioned.... its about a 5 or 10 degree offset. I've heard of Busa guys running an offset pin to accomodate certain cam swaps (where the pin isn't straight, but is instead at an angle). Dont know if that is possible here or not.
Btw, I know that people do these swaps / combinations are possible (K1/K2 cases with later heads), but I dont know the particulars of how they make it work, so take some of my comments with a grain of salt. I'm sure that there is someone here that can tell you exactly how to make this work... but thats not me. Just giving you some potential issues to watch out for
Oh, one last thing, when it comes to the K7 heads, make SURE the valves are in good shape. Those Ti valves are easily damaged, and are EXPENSIVE to replace. And whatever you do, do NOT try to hand lap them!!