changed the heads on my 749/924 to the later model s heads ....yes I'm sure I picked up top end power ,I get an almost two stroke like rush @ 8000 rpm.
but this has come at some expense .Where it used to pull strong from 5000 with the standard heads and high velocity porting it won't do that anymore.
I'm wondering if I can go back to the standard cams but keep the s heads?
Also don't forget that a port with high velocity will make more torque down low and in most case's loose some on the top end due to the flow restriction. An 84 crossfire corvett with it's 1 inch square intake manifold ports would fry the tires all day long, but they would run out of breath at high rpm. So it is a trade off and a compromise.
changed the heads on my 749/924 to the later model s heads ....yes I'm sure I picked up top end power ,I get an almost two stroke like rush @ 8000 rpm.
but this has come at some expense .Where it used to pull strong from 5000 with the standard heads and high velocity porting it won't do that anymore.
I'm wondering if I can go back to the standard cams but keep the s heads?
The higher and faster the cams lifts the more airspeed the ports will see. Putting the bp cams back in will make it slower. You need a real dyno analysis , you may find with the fuel dialed to the new s cams and heads you will be a winner all round.
If your going to be doing some diy work i would focus on the combustion chamber . The chamber side shrouding wich blocks the inlets valves line of sight to the exhaust valve is where the power is hiding.
Another thought ,the fuel map was never optimised for your high velocity heads either . There may have been another load of hp to come.
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PS: I did degree the cams to the original settings ...no problems at all at idle .I understand from reading Brads work that the revised settings were to fix an idling issue. Also the map I'm using from Ducshop was developed for my exact ,well except for the exhaust, setup. The engine feels very crisp and responsive on the throttle .Very difficult in my local to get to a dyno ,800 miles minimum.
Reading Seespotweld's problem makes me wonder whether going the "full Monty with aggressive cams and head work is the way to go on a (mostly) street bike? I have an 03 749s with a 924 kit and a half system putting out about 114 hp on the dyno. i recently purchased 06 749s heads that were worked on by Martin Brickwood - his collets, valves and ports polished. Was going to throw on a 54mm full system have some extensive dyno work done and see what I'd come up with. however i have no interest in having the bike make all its power north of 8000 rpm's. the fun with a big bore kit is the increase throughout the power band. what do you guy's think??
Reading Seespotweld's problem makes me wonder whether going the "full Monty with aggressive cams and head work is the way to go on a (mostly) street bike? I have an 03 749s with a 924 kit and a half system putting out about 114 hp on the dyno. i recently purchased 06 749s heads that were worked on by Martin Brickwood - his collets, valves and ports polished. Was going to throw on a 54mm full system have some extensive dyno work done and see what I'd come up with. however i have no interest in having the bike make all its power north of 8000 rpm's. the fun with a big bore kit is the increase throughout the power band. what do you guy's think??
A well re-worked/ported head will make more power everyware from 4000rpm up as long as the airspeed is correct. The port chokes are 2x 29mm barrells wich is about right for a 924cc and un masked 38mm valves with a cam that lifts to 11.5mm. I dont think you will be dissapointed .
On another note seat of the pants dyno feed back has no relavance unless the fuel is perfectly optimised on the dyno/track for each combo thats being tested.
__________________
life is work
For Ducati engine blueprinting/crank balancing/performance cylinderhead prep/ porting / big valve conversions-www.cjsracing.co.uk
For 1st class dyno-tuning ,mapping, custom eproms- and a whole load of other cool stuff www.hypertrick.net
Just a question. In this paragraph, "If your going to be doing some diy work i would focus on the combustion chamber . The chamber side shrouding wich blocks the inlets valves line of sight to the exhaust valve is where the power is hiding. "
Does it refer to the red rounded zones in the photo? The photo is a 996 head, sorry.
Well, I have put a thinner base gasket in order to adjust the squish (from 0.6 to 0.2 mm). This downs 3 cc the volume of the combustion chamber and the compression ratio increases near 12:1.
I think I could grind these zones in the combustion chamber (increasing the volume up to 3 cc more or less) and maintain the compression ratio near the original 11.5:1.
Just a question. In this paragraph, "If your going to be doing some diy work i would focus on the combustion chamber . The chamber side shrouding wich blocks the inlets valves line of sight to the exhaust valve is where the power is hiding. "
Does it refer to the red rounded zones in the photo? The photo is a 996 head, sorry.
Well, I have put a thinner base gasket in order to adjust the squish (from 0.6 to 0.2 mm). This downs 3 cc the volume of the combustion chamber and the compression ratio increases near 12:1.
I think I could grind these zones in the combustion chamber (increasing the volume up to 3 cc more or less) and maintain the compression ratio near the original 11.5:1.
Am I right?
Thanks
Hi
It does not apply to a 996 head. There is no shrouding or power to be had grinding anything here !
__________________
life is work
For Ducati engine blueprinting/crank balancing/performance cylinderhead prep/ porting / big valve conversions-www.cjsracing.co.uk
For 1st class dyno-tuning ,mapping, custom eproms- and a whole load of other cool stuff www.hypertrick.net
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