Maybe off the wall but I had to ask
Anyone know what is involved mechanically in fitting 851 heads on a 906/907 lower end ?

Apart from the 2mm longer stroke on the 906/907 it should go straight on. It would need 2mm thick plates under the barrels to stop the pistons hitting the heads.

I doubt it`ll work. The 851 piston is 94 vs 92mm on the 907ie. The heads as the cylinders of a 851 are square shaped, the cylinder is flat with no projecting cylinder wall and uses a head gasket. While the stud hole distance should be the same also the oil and water channels have different shape & size.

G.

You would need the 851 (92x64) cylinders, pistons, and heads. As mentioned above, you would need 2mm spacers beneath the cylinders to deal with the 68mm stroke. One problem with using spacers that thick is the 4V belts get very tight.

In the past I have used 916 pistons (94mm) with 888 (or 916) cylinders (94mm), but the 916 pistons have the pin height moved to accommodate a 66mm stroke. Then I only had to use a 1mm base gasket to achieve the same goal. But less stress on the belts. And you can buy those base gaskets from Ducati, no special plate required.

Right, the 94mm are the 851SP/888 models not the Strada.

What about the frame fit, they look to be much larger than the stock heads
Reason I'm asking I ran across a great deal on a complete set of heads from a low mileage bike
Might pick them up any way just to add them to my stock for the future

this is a complete 888 engine. (I wonder if the lower side of the tank had to be modified)

Definately. And with 17 inch wheels, there would be a clash between the front wheel & the oil cooler/cylinder head when the fork is fully compressed. (At least with the 996-Engine)