Hi all. I’ve just had a much better look at the cylinder heads I picked up as part of a bitsa 900/962 engine we’re building up, and think I should have paid a bit more attention when I looked at them. Especially as they are different colours. As below. Both have a 43mm Inlet Valve. Both have a 38mm Exhaust Valve. The Vertical cylinder has a Camshaft marked VHT. The Horizontal Cylinder has a Camshaft marked OHT. I believe that makes them 900SS heads, not monster, with the bigger valves and better set of Camshafts. Unless anyone says differently? Now the bad bit: The Horizontal one is stamped V2 with a manufacturing date of 12/95 The Vertical one is stamped V1 with a manufacturing date of 1/91 Now I understand the V2 is a development of the V1, but am unsure if the only real difference is the valve seat material – can anyone confirm this or point out any other differences? The big question is of course, as they both have the same Valve size, and have a matched pair of Cams(I think), has my plan to run them on the same bottom end got any flaws? Thanks Nasher
OHT and VHT are correct cams for SS and early M900 (prior to 'W' heads). AFAIK 'V' and 'V2' heads are basically the same other than the valve seats (which could be upgraded in the 'V'), I think you might find more info on this on BikeBoy's website; BikeBoy.org
From Ian Falloon's "Ducati Belt-Drive Two Valve Twins - Restoration and Modification" with regard to the 900SS heads ; From January 1992, the valve guides were changed form cast iron to aluminium bronze. All cylinder heads featuring these new valve guides were identified by a "V1" marking on the timing side cover.
Thanks for the comments everyone. The Vertical head is definitely stamped with a V1, and also has a casting date cast in of Jan 1991. I assume it's probably one of the first castings to have the Aluminium Bronze insert pressed in and made it onto a bike for sale @ Jan 1992. So if the V1 heads have the Aluminium Bronze valve seats, what is the difference between the V1 and V2 heads? I really need to understand this before I commit to using them together on the same engine. Thanks Nasher.
As an aside, and to add confusion, the data pack that came with my 97 M900 includes documentary evidence that the Cylinder heads were changed when the bike was new to older, bigger valve jobbies. The Cams are marked VHT and OHT, but the heads are stamped just with a 'V', no 1 or 2. I'll have to have a look for the casting date on them. Nasher
I can understand your meticulous approach as you want the best set-up for your engine, but I wouldn't worry too much about the valve seats even if they are different as it takes approx 15K miles before valve recession makes reshimming a priority even on the earlier heads. I guess you are routinely changing the guides anyway, the only other difference I can think of is whether both heads have external oil feed type (banjo fixings with short flexible oil tube) or internal (no hoses needed). Also a foot-note, i'm sure you already know, but have you checked to see if you have late-type cylinder head studs installed or have you fitted new ones anyway?
Chris hi. I'm not worried about the valve seat material at all really, I don't do enough miles for that. I'm concerned what other differences there may be that haven't become apparent. Are the port sizes the same?, Do they flow the same? are the compression ratios the same? anything that will cause an imbalance from one cylinder to the other. Both heads, and the alternator side cover, have provision for external oil lines, plus I've purchased a set of APE studs. Nasher
Hi Nasher Let others confirm but I am 99% certain that the "V" is the most important part and you can ignore the 1 or 2 that follows as far as comp ratio/porting differences are concerned as the 2 valve engines weren't that technical around that time.
I've been all over the heads and measured everything I can get to. The V1 head has a slightly smaller inlet track, but nothing that can't be matched quite easily as part of the cleaning up process. From what I can measure the volume of the combustion chamber could be slightly bigger too, suggesting a higher Compression ratio on the later V2 head. I need to drill a hole in a disc of Perspex and find the pipette I know I have somewhere to measure the volume exactly, a process I've not carried out in a few years. Would be a shame to open the later head up to match the CR of the older one, but I'll see what the difference is when I've measured it. Nasher.
Re: V1/V2, I think any comp ratio differences you find will not be "by design" also when it comes to port comparison you need to compare like for like, i.e. horizontal/horizontal, as the std ports were subtly different anyway. Sounds like you were going to check anyway, are you sure you're not going racing?
Chris Hi. Nope, not going racing:smiley: This build is purely for fun, and whilst the engine is down to it's last nut and bolt we might as well do everything we can to build it up to be as smooth as possible on our small budget. Tricks like matching Cylinder head volumes take time, but are completely free to do, and can only have a positive effect on how the engine runs. I'm sure you're right that manufacturing tolerances etc are responsible for the differences, which is of course where Blueprinting comes in. We're not going that far, but in an effort to reduce vibration we have already matched the conrod little end weights, and have taken a small skim out of the back of one piston to match it's lighter brother. Again all free to do and can only have a positive effect. Having spent many years mucking about with Kawasaki Z1000's, and many different mainly Japanese outboard boat engines, I'm quite impressed at how well the 900 engine is manufactured. Nasher.
