We've heard of the acW1 and 2, but our data plate doesn't include the 'W', just AC1. So, I'm guessing it wasn't designed to have the cylinder cooling. Although, if it was just the cylinder head that was different (with water in/out pipes), as ours is set up to run with a raw water pump already, perhaps we could get such a cylinder and have a quieter and cooler/smoother engine. Are those correct guesses and likely outcomes?
Looks like your engine was always the aircooled AC1 version, and previous owners may have 'added' parts from the watercooled version. If money was not a concern, then the water cooled parts you need will fit straight onto your existing crankcase. However in reality the money needed to achieve this would be significant, and been honest these mini six engines are an old design hence there are now better engine options out there. Specifically the specialist water cooled spares are becoming difficult to source, and these engines are not quite in operation when compared to a modern equivalent.
On the forum people talk of the direct top injector models (straight into the cylinder head top) being more reliable than the side injector model, like we have. If we just switched a top injector cylinder head for our side injector one, would that simply involve taking off the old head and bolting on the top injector head?
If your keen this modification is possible, and requires as a minimum the following: cylinder head with injector (this item is identical to the later Petter AD1 engine), direct injection piston, and cylinder head and barrel cowling.
It will work, but wont be ideal, as the later AC1 series 2 engines have a slightly different camshaft lobe profiles, if you really want to explore this option, the cheapest solution would be to buy a busted AC1 series 2 engine for the parts you need.
IMHO the later engines are no more reliable, they are slightly more powerful and slightly better on fuel consumption, on the downside when they become worn they can become difficult to start, as you have no oil priming facility on the later engines. Also they are noisier in operation been direct injection.
Drilling the Allen cap screws sounds difficult. I'm guessing the Allen screws are going to be hardened steel, not. Do you guys know if the screws are hard metal to drill?. We'll keep trying the ordinary ways to get them lose, but it would be worth knowing if they're going to be hard to drill, just in case. Then we can get suitable drill bits.
They are not hardened, but they are tough, it is possible to drill them with high speed steel drill bits, but with frequent resharpening, remember you just need to drill the heads off and no more.
Pleased to hear you say the gearbox we have is right for the engine model we have! (Have seen the same g/box now on a ?AC1 petter on utube - a newly gold painted engine running beautifully.) But I guess the parts for this Italian g/box aren't petter made... so where on earth would we find parts (eg: clutch plates)?
The gearbox has a wet clutch, and if its slipping, you should only need to adjust it, as for spares for these boxes your correct, this was an item that Petters bought in (same with the Hurth gearbox on the mini twins) I can only suggest a google search, as I have never needed any parts for the mini six gearbox