Has anyone put a set of 800 heads on a 750 motor? Do they bolt right up? they have the same bore, so I would imagine that they did not change the bolt pattern, but I could be wrong. Bigger valves are always better.

cheers,

Haven't heard of it yet. Will the oil galleries line up??

i have never heard, that Ducati have made 800cc engine????? More details, please....

Monster S2R 800:
http://www.ducati.com/en/bikes/my2007/M ... MS2R800-07
And there also was a SS800.

Do a search at DML, US Monsterlist: http://www.ducatimonster.org/smf/index.php
for compatibility.

Paso 750 & SS/Monster 750 engine are not the same. Compression, oilcoolers etc.

Perhaps, the heads could be fitted, I wonder.
Ciao

Thanks! I havent had time to look Monsters and Supersports, cause have to concentrate to Pasos and STs... Too little time and too much work to do....

I'm also interested in fitting 800cc heads - will they fit?
Cheers,
Mark

This is what I have found out so far.
The 800 heads will indeed fit on 750 motor.
Intake and exhaust bolt right up, and piston bore and bolt pattern are the same.

The benefits;
- Bigger valves, 900 size.
- Better Flow characteristics

The bad;
- Loose your mechanical tach drive
- The combustion chamber is larger, so compression ratio is much lower. You will need really high compression ratio 750 pistons, or 800 pistons. (13:1 750 pistons)
- 800 cams have a slightly different bearing arrangement, so you are stuck with 800 cams, unless you know a machinist. Earlier model cams can be fit with a custom spacer to take place of a third bearing.

The 800 pistons have a higher deck height to offset the larger combustion area. So, the stock 800 pistons might be used in the 750 motor as high compression pistons. First person to try this wins a gold star, and the admiration of the list.

The bolt on horsepower mod seems to be 800 heads, some HC pistons, and 900 cams with a special spacer to fit the 800 heads. Apparently good for about +15hp. Pistal pistons seems to be the choice of most, but FBF pistons are close second.

Cheers,

if you look at dynoruns (moto.one.com.au) of tuned 900cc Duc engines which get +10-12hp with all kind of mods (944kit or HC pistons, ported heads, bigger valves etc) +15hp on a 750 engine is quite unrealistic. However there is always an impact on torque which is more important.
I wonder how suitable a Duc engine with 13:1 compression would be for normal street use.

G.

To your first question, the 750 motor has much more room for improvement than the 900 motor does, so the same modifications on the 750 will result in much higher gains. and for the standard caveat; your results may vary.

Yeah, I guess I failed to exactly clarify the compression ratio thing.

Since the 800 heads have such a large combustion area, you will need 13:1 pistons for a 750 to get the compression ratio back up to around 10:1. Since you are mixing parts, you have to do some of your own homework. No one I know has used high compression pistons for the 800 yet, I suspect that they will have a higher compression ratio. Pistal makes a nice set for the 800 which might be your best bet. You can always adapt with a stack of base gaskets to get the compression ratio back down to where you want it.

Cheers,