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998 heads on a 996 motor

3K views 19 replies 9 participants last post by  johnnie27 
#1 ·
Is it possible? Have a spare 998 motor that I have caniblized a litte bit, has a broken bolt in the motor for the kick stand that i can't get out. Was wondering if the heads fit on the 996 motor as it has a better vallve angle and bigger valves, plus i have a set of 996r cams too.996 motor has the pistal pistons in it & would benefit with bigger valves and shower injectors. Motor is just sitting there doing nothing and if the bolt can't be removed it is a useless motor for me.
 
#6 ·
I have a sset of 458 g cam for the intakes (new), nothing for the exhaust . Understanding is they are hell on the rocker arm though. To use them i would need to port the heads i assume. I didn't do anything to the heads on the 996 motor just used sps cams. Wanted to put bigger valves in it which is why i was asking about the heads on the 998.
 
#7 ·
Yes. I have thought about doing it. In addition to what bradblack said, the stud spacing of the cylinders are the same but either the 996 cases or 998 cylinders will have to be machines. The outer diameter of the 999 cylinder is too wide for the 996 cases and won't slide in. If you look at the 996 cases you will see something like a 45degree taper right were the piston slides in. If that were gone it would be a direct swap.

If I was going to do it I would begin by machining .5mm off the 998 cylinders.
 
#8 · (Edited)
Already have the pistal pistons in the 996 , would have to balance the motor to use the 998 pistons . Was looking at options for increased power without incurring more in costs. Was thinking 998 heads would be a great swap out option if they fit.
Going to re-dyno the 996 motor tonight, crank position sensor failed in the middle of tuning the bike so going see what hp the motor makes with the revised fuel map as it was running rich before the sensor failed and was only making 118 @ rear wheel for power. Hopefully will see 125 or better today.
 
#10 ·
Fix the broken bolt. Have a professional do it if necessary.

Bigger valves aren't necessary.

My 851 with the 996 motor makes 147 at the wheel using standard 996 heads and valves and that's at 9,000-9,500 rpm. No need to rev it. Power comes from hi comp pistons and SPS cams. (It has a 996RS crank and Carrillo rods, but those are for less stress/more reliability on the motor, not more power.) Externally, it has the 50mm exhaust and Microtec ECU.

With your Pistals and SPS cams you should easily see 130++ if you set the squish, time the cams well, and are able to make a good map for it (though there are limited ECU options with the 996 harness).
 
#12 ·
Ok...146.71.



Here it is with an overlay of a Microtec tuned 1098S and matching it up to 9,000 RPM.



This is at Moto Corse Performance (Chris Boy's shop) in Florida.
 
#13 ·
How did you make that much power with essentially a stock motor assuming pistal racing 2000 Pistons are worth 6-8 hp as drop ins

Chris has a 996 sps in the U.K. Making almost this hp but that motor was fully developed heads valves etc etc


Does the crank increase the stroke , sorry just keen to see what your magic source is

Sent from Motorcycle.com Free App
 
#19 ·
How did you make that much power with essentially a stock motor assuming pistal racing 2000 Pistons are worth 6-8 hp as drop ins

Chris has a 996 sps in the U.K. Making almost this hp but that motor was fully developed heads valves etc etc


Does the crank increase the stroke , sorry just keen to see what your magic source is.
I know the dyno is more generous (perhaps 3%/5hp?) than the one at Ducshop for example, which is why it has more context with the tuned 1098. I like that the torque is almost equal and that peak power is at just 9,000 rpm. And for the record, Boelo Lussenburg's Next Gen runner-up corse 888 with full 996RS heads made 141 on the same dyno.

The heads had a bit of cleanup and the intakes look and feel exceptionally well matched. I'm not sure what little secrets TJ (at Moto Union) has in his bag, but his skills are quite well regarded.


Ben Fox supplied the lightened and balanced 996RS crank/Carrillo rods/CP high comp piston assembly. The pistons were from a custom batch to his specifications.




TJ timing the SPS cams to his specs.
 
#18 ·
You might look at your chain and sprockets as well given how erratic the curve is with the smoothing set on 5 (max) I often run the superbikes on 3 and they look close to what you have on 5.

I am not familiar with the superflow dynos first hand but believe they are a high quality dyno. The shop that ran it also is top notch so my guess is that the number is legitimate on the superflow when run in DJWHPW setting which given history is probably
DJ = dynojet
WH=wheel
PW=power

So if I am guessing correctly this is scaling the HP up to where superflow thinks the power would be on a Dynojet dyno. Dynojet dynos have historically been labeled as reading higher the Factory dynos I do not know where superflows stack up. This may be a way to give the customer a number that is higher than the dyno would have read otherwise what we call a "hero number" They are reading in SAE which is good for the US but I wonder if the high reading is in the DJWHPW designation as for the mods done I have to agree it is a decent amount higher than I see on Dynojet 150 and 250i dynos.

In the end I would care mostly about the curve than the number and keeping this run to compare to later runs to verify the health of the motor. Numbers from different dynos are some times more of a problem than a help, I care more what the curve looks like when comparing from different dynos.
 
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