P11 engine build
- Thread starter tribonnie
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Schwany
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Yes it can all work if the barrels and cylinder head are both for a Commando 750. A Commando 750 head will fit on P11 barrels, but the P11 barrels need to be drilled and tapped for 3/8-26 bolts in 5 locations. Rods, pistons, and ect are or can be the same. Although the Commando pistons will be flat top and slightly higher compression than the dished pistons P11 used originally. The cam has to be for a pre-commando in P11 cases, unless some additional modifications are made to the timing side case to support a Commando cam and ignition in a Commando timing cover. I might be wrong about the thread count on the 3/8" head bolts, but a stock P11 had 5/16" bolts in the 5 locations.
Shorter answer is... Yes I've done it. Go for it.
EstuaryBoy
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In addition to the above, might be prudent to point out the rocker oil feed positions are different, but obviously not insurmountable, but would check that the P11 head steady can be fitted to the Commando head?
Again, I defer to yer man above to elaborate
Again, I defer to yer man above to elaborate
Schwany
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Adding more to my steaming pile of info:
I had one of Raber's machinists do the drill and tap stuff for the 3/8" bolts in the P11 barrels, and used a Commando head for a short period while my P11 head was getting ported by Fred Barlow. Once I got the P11 head back I put it on the P11 barrels with the 3/8" bolt support after drilling out the 5/16" holes to 3/8" or whatever it took to get the larger diameter bolts through the P11 head. I used braided PTFE oil lines for the Commando head, and the P11 head. The cross over line ends up being a bit long on the top fed P11 head, but it works. Fairly certain I used the same head brace I made from aluminum bar stock for both heads as well. I still have the Commando head, which is basically like new but really old. I'm slowly, when I fee like it, improving the ports on both intake and exhaust as well as using it to hold and modify Commando intake manifolds so they can be used for CR and FCR Keihin carburetors. Improving the ports is not hogging them out. It is cleaning up the crappy work Norton did and increasing the entrances to 31.5 mm and blending them in to a 29.5mm neck with a minimally raised roof before the valve guide. Not quite Narly, but Narly enough. All done with emery cloth and my fingers. Slow and steady wins the race. Also adding some epoxy to the floor and reshaping it a little. I'm basically sort of copying what Fred Barlow did because it works really well without any loss of bottom end torque with an SS cam and properly seat of the pants dyno tuned FCRs.
I had one of Raber's machinists do the drill and tap stuff for the 3/8" bolts in the P11 barrels, and used a Commando head for a short period while my P11 head was getting ported by Fred Barlow. Once I got the P11 head back I put it on the P11 barrels with the 3/8" bolt support after drilling out the 5/16" holes to 3/8" or whatever it took to get the larger diameter bolts through the P11 head. I used braided PTFE oil lines for the Commando head, and the P11 head. The cross over line ends up being a bit long on the top fed P11 head, but it works. Fairly certain I used the same head brace I made from aluminum bar stock for both heads as well. I still have the Commando head, which is basically like new but really old. I'm slowly, when I fee like it, improving the ports on both intake and exhaust as well as using it to hold and modify Commando intake manifolds so they can be used for CR and FCR Keihin carburetors. Improving the ports is not hogging them out. It is cleaning up the crappy work Norton did and increasing the entrances to 31.5 mm and blending them in to a 29.5mm neck with a minimally raised roof before the valve guide. Not quite Narly, but Narly enough. All done with emery cloth and my fingers. Slow and steady wins the race. Also adding some epoxy to the floor and reshaping it a little. I'm basically sort of copying what Fred Barlow did because it works really well without any loss of bottom end torque with an SS cam and properly seat of the pants dyno tuned FCRs.
