Hi All. I've had a look through the forum and can't really find what I'm looking for. I wonder if there is any experience or knowledge about what I'm looking to do. I have a 2002 748 that I love. The engine has 60,000km on it and burning some oil and is surely down on power a bit. I have a crankshaft and rods from a '02 Monster S4 916 and a pair of heads[amendment - I meant pistons!] and cylinders from a 916 (not sure what age but late 90s I think. Both the crank and pistons/cylinders are supposedly from a low km engines and they certainly have this appearance. What I'm thinking of doing is pulling the engine down and rebuilding it as a 916. I think a few of the problems encountered with these builds are covered but here is my thinking: - I would be swapping a 3 phase alternator crank for another 3-phase crank so I shouldn't have a problem in that area - Existing cylinder heads will be used and at this stage I am thinking of just doing the seats and seals but could open up the head a little to unshroud the inlet valves and reduce the compression a little, back to 'normal levels'. - I'd be keeping the throttle bodies and manifolds as is from the 748 with a 916 EPROM chip for the 1.6M ECU used. - My 748, being a 2002, has the drop cam testa bassa heads like the S4 and ST4 and I'm not expecting any compatibility issues As far as I can tell I shouldn't run into any real problems but am seeking any guidance on what to look out for such as: - Cylinder squish issues to watch out for - Existing 748 valves to 'new' 916 piston clearances - Anything not fitting or playing nicely I'd appreciate any insights if anyone has any. My riding style is more suited to mid range torque rather than race-track redlining which is partly why I am considering this option and it's a fair bit cheaper than an 853 conversion and I get an additional 63cc. Cheers, Martin
http://www.ducati.ms/forums/56-superbikes/602849-using-early-748-heads-early-916-motor.html This may help also the throttle body diameter on a 748 is smaller than a 916
When I had my 853 engine built, I have at the back of mind I was told 916 barrels don’t fit the 748 cases. Someone like @nelly or Rich Llewellyn should be able to advise you. Andy
I think the 916 barrels fit the 748 cases but the 996 won't, I now await slapped wrists if i am wrong. Steve
What makes me sure the 916 barrels fit is that they are often used for the 853 conversion but need skimming by a few mm, the 996 base diameter is to large for the 748 cases. Steve
Sounds like you have most parts to make it work ok. The crank should swap just fine. You have pistons, cylinders etc. The heads should be fine as is, replace the stem seals and give them a refresh just because you can. The bigger bore unshrouds the valves, nothing else to do. Compression should be fine as you'll be using 916 Pistons, crank and cylinders etc. I'm sure the 748 heads and 916 are the same....? Again, can't be sure, but I think the locating dowel position moved, the one in the case cylinder surface. Not sure when, but if it has, you can measure up and redrill it. The 916 barrels should fit just fine. There's an issue using them for the 853 conversion which as mentioned requires they be skimmed a little.
I recall from memory that if you use 916 pistons on it then the cylinders need skimming as the throw on the 748 crank is less, but if you buy 853 specific pistons the gudgeon pin hole has been moved to suit the 748 crank and 916 cylinders.
Thanks for the replies everyone. Yes, you certainly can't put 916 pistons on a 748 crank otherwise all you get is a low compression 853. You can shave the cylinders but then you have problems with throttle bodies fitting into the V and timing belts being too long as well as exhaust not fitting right either. For an 853 conversion you can use the 748 bottom end with 916 cylinders but need special 853 pistons to get the compression right. This is the expensive bit. What I'm doing is fitting a 916 crank as well. Thankfully I have a 916 crank from a 2002 Monster S4 so it has the same generator mounting but was wondering if there are any other little issues to look out for. Thanks for your input Nelly, hopefully the dowel won't be an issue or it can be moved. As far as I know the cases are the same for all 748s and 916s. The 996 had a different case to accommodate the 98mm bore so the head mounting studs had to be moved further out
Just for reference ferracci.com still list the 94mm pistons for the 853 conversion and are on sale at the minute for $420us
I recall reading/hearing that 748 heads, whilst the same casting, have a smaller combustion chamber than 916? Not sure if you're using these or 916 heads though...
Indeed but he also said; So I wasn't sure and had heard the 748 heads were slightly different. IIRC the valves may also be seated less deeply?
