Being new to this Ducati "thing", I'm wondering, is the S4 engine identical to the 916? What is the difference between the 916 and 748? Say I bought a set of heads off of a 748, are valve sizes, cams and whatnot the same? Is this like the small block Chevy of the Ducati world, the 748/916 engine? Is there any difference between the mid 90's 916 and my S4 engine?
Thanks, Robert
Quote from: corndog67 on May 26, 2009, 07:11:27 PM
Being new to this Ducati "thing", I'm wondering, is the S4 engine identical to the 916? What is the difference between the 916 and 748? Say I bought a set of heads off of a 748, are valve sizes, cams and whatnot the same? Is this like the small block Chevy of the Ducati world, the 748/916 engine? Is there any difference between the mid 90's 916 and my S4 engine?
Thanks, Robert
No. Your engine isn't identical to a 916 engine.
The biggest difference between the 916 and 748 engines is the displacement. The bore and stroke of the 916 are 98mm and 66mm respectively while the 748's are 88mm and 61.5mm.
Consequently, I'd guess that 748 and 916 heads are not interchangeable, though I don't know for sure. (There're definitely people here that can tell you, maybe they'll chime in.)
Regardless, the 748 heads (and 916 heads also), will not fit your S4.
The biggest difference between the S4's engine and the engine in a 916 is the height of the cylinder heads.
If you put a heads from a 916 on your bike's engine the horizontal head will hit the front tire.
Specifically, the exhaust cam is 10mm lower on the S4 heads vs. the 916 heads.
Due to this, your existing belt covers wouldn't fit properly.
Also the 916 heads don't have the bosses on 'em for mounting the battery tray.
916 cam belts are longer, to work with the exhaust cam placement.
The ST4 heads are the same AFAIK.
Here's a ton of tech info to look at:
http://www.bikeboy.org/performance.html (http://www.bikeboy.org/performance.html)
Apparently, the 916, S4 and 748 all have the same valve sizes:
http://www.bikeboy.org/duccamspec.html (http://www.bikeboy.org/duccamspec.html)
748 heads are likely going to have smaller combustion chambers, and I *think* the intake valves are closer together to get 'em to fit the smaller bore.
Ramses and Speed, thanks a lot. Good info is kind of hard to find for these bikes. Lots of bad info out there, too.
Those Bikeboy sites are excellent.
Robert
I believe the ST/S4 heads are referred to as drop cast.
Cams have less duration also.
Can I drop in 916 cams? I now know that the S4 heads have the exhaust cams lower in the head, are the cams interchangeable? How are the manufacturing tolerances? I know on a Honda, you can drop in a set of factory made cams and the valve adjustment generally won't change, due to the tolerances that Honda adheres to. How about Ducati? Am I opening up a can'o'worms if I decide to pull the trigger on some engine work? It runs pretty good right now, but if a little is good, more is better, and too much is just right, right?
Also, does anyone have any idea who makes Ferraci's pistons, or valves? Is it someone like Arias, Jahns, JE, Kibblewhite, TRW, Manley, Stealth, or any of the other high performance manufacturers? If so, our shop has a working relationship with nearly all those guys, I'd be surprised if I couldn't scare up a set of big bore stuff for quite a bit less than the $1455 I've been quoted. How much are 2 pistons to make, anyway, I know it isn't $500 each. I'm pretty sure LA Sleeve or someone like that can bore and set up a set of Nikasil cyliinders for a reasonable price, too.
What do you guys think? Am I setting myself up for disappointment, or is this a workable deal?
Quote from: corndog67 on May 28, 2009, 05:06:54 PM
Can I drop in 916 cams? I now know that the S4 heads have the exhaust cams lower in the head, are the cams interchangeable? How are the manufacturing tolerances? I know on a Honda, you can drop in a set of factory made cams and the valve adjustment generally won't change, due to the tolerances that Honda adheres to. How about Ducati? Am I opening up a can'o'worms if I decide to pull the trigger on some engine work? It runs pretty good right now, but if a little is good, more is better, and too much is just right, right?
Also, does anyone have any idea who makes Ferraci's pistons, or valves? Is it someone like Arias, Jahns, JE, Kibblewhite, TRW, Manley, Stealth, or any of the other high performance manufacturers? If so, our shop has a working relationship with nearly all those guys, I'd be surprised if I couldn't scare up a set of big bore stuff for quite a bit less than the $1455 I've been quoted. How much are 2 pistons to make, anyway, I know it isn't $500 each. I'm pretty sure LA Sleeve or someone like that can bore and set up a set of Nikasil cyliinders for a reasonable price, too.
What do you guys think? Am I setting myself up for disappointment, or is this a workable deal?
You will need to re-shim if you change the cams. Even if tolerances were identical between cams of the same model, these have a different curve and possibly a smaller base circle.
Ferraci was using Wisco pistons for their kits the last time I checked. They don't manufacturer anything, they just relabel.
Quote from: corndog67 on May 28, 2009, 05:06:54 PM
Can I drop in 916 cams? I now know that the S4 heads have the exhaust cams lower in the head, are the cams interchangeable? How are the manufacturing tolerances? I know on a Honda, you can drop in a set of factory made cams and the valve adjustment generally won't change, due to the tolerances that Honda adheres to. How about Ducati? Am I opening up a can'o'worms if I decide to pull the trigger on some engine work? It runs pretty good right now, but if a little is good, more is better, and too much is just right, right?
916 cams work
The majority of 748 cams work - Some 748 heads were a bit wider and becuase of that the rockers may not line up exactly.
It doesn't, IMO, make sense to upgrade to 916 cams. You'll want to look for SPS cams and I have heard that 748R intake cams combined with 916 SPS exhaust is the hot combination. I was able to find a nice set of 748R cams for 350 but am still looking for a set of SPS.
Good Luck
Here's some info on ducati cams, 4V cams are about 1/4 of the way down the page.
http://bikeboy.org/duccamspec.html (http://bikeboy.org/duccamspec.html)
It appears that the STD, S4, and S4R all use the same exhaust cam.
Meaning, the 916 exhaust cam is the same as the S4 exhaust cam.
S4 uses an intake cam that closes 10deg earlier than the 916.
Apparently, this is a good thing, see my link below.
AFAIK, the so called 'SPS' cams are what is shown as 996SPS.
Also, here's a bit of info on how the S4 is different from 916 and ST4:
http://bikeboy.org/monsters4diff.html (http://bikeboy.org/monsters4diff.html)