I've got a blown head gasket on my 996 and the cylinder head has some corrosion. I've read some posts on hear about similar issues - has anyone had the head skimmed and re-timed? There doesn't appear to be much space for skimming before the valve seats are reached. I've heard this mostly affects the vertical cylinder - the horizontal cylinder looks ok when I've looked down the intake manifold (looks dry anyway!). Bike has only done 3,200 miles. Could anyone recommend a mechanic who can do this sort of work in the North West please?
Because they're only a single cylinder you shouldn't have to remove much material, just clean them up. You can't really remove too much off the surface anyway, regardless of touching the valves as it will effectively make the timing belts longer. You should remove the same level off the second head at the same time to keep it balanced. Make sure you use demineralised or distilled water with good corrosion inhibitor in the system.
I had 1mm skimmed off my 916 heads for a compression ratio boost along with gas-flowing as part of a tuning exercise. It does mean the belts are now effectively longer but fitting larger idler pulleys recovered that and the cams needed to be degreed to get the timing back but it did give a useful 'kick' in power. Don't know if the same could be done to a 996, are the heads much different?
Cheers Borgo - spoke to Colin but he's not a 'belts' guy, but he pointed me to Rich at Moto R in Ruthin. He reckons it can be welded and skimmed so I'l be taking it there.
I don't know how different the heads are, I'm trying to avoid the larger pulleys, retarded cam timing, etc - think it would be cheaper to get another head.
Rich is a good guy. He’ll be able to help. Tbh, for what they fetch secondhand, youd probably be better getting another one and build your parts into it. Probably cheaper and youdont have to start with different base gaskets to get the squish and piston clearances back to spec
A pal is selling almost an entire a 916/ST4 engine in bits, if the heads can be made to work with your parts swapped into them, the whole lot is offered for sale for £100 - collect in Aughton, near Ormskirk https://www.ducatiforum.co.uk/threads/916-st4-spares.104193/#post-2281593
Yeah - I'm looking out for a head as well. Rich said it's not that much to get it welded and ever so slightly skimmed and I may not have to even think about clearances, etc.
Indeed they do plus, they're 916 and so, I believe, have different stud spacings. IIRC, the 996 went to wider stud spacings due to the bigger bore meaning there wasn't enough material around the cylinder, leaving too thin of a cylinder wall, hence the many failures of early 996cc engines in WSB racing with the 916SPS being the homologation 996cc model?
I doubt they'd warp, given the thickness and how solid they are, typically car heads are much longer and thinner and even they don't always warp unless seriously overheated. Did it even overheat much? I had a head gasket fail on my 916 when it was quite young, there was no damage to the head just coolant leaking over the rear of the engine.
I don't quite understand why a corroded head that hasn't warped needs skimming? Perhaps Alexlittle could explain?
It's the corrosion that actually made its way into the cylinder (see pic). You can see where the corrosion has crept into the cylinder wall and where the coolant has left a slight burn mark. So the head either needs skimming past this pitting so that the seal is flat again or spot welding to fill the pitting, and then skimmed flat.
A cylinder replating company like Langcourt; https://langcourt.com/ should be able to repair that for you.
Sorry Alexlittle I could not see on original pics. I understand now it doesn't look that clever. Ally welding difficult, could possibly be tig welded to build up that area, then skimmed back to standard? Not necessary shave the whole head? Just a suggestion.
