About 6 months ago I picked up a 1981 FLT Shovelhead for a really good price. I decided to put a S&S Super E carb on it, and when I pulled the old zenith carb off I was plesently surprised to see one band style manifold and one O-ring style manifold. I thought that O-ring style heads were never available for the 83"ci shovels. After looking around a bit it seems that this might indicate that one head was pulled from a 73"ci shovel and the other from a 83"ci shovel. This makes it impossible to get a good seal on both intake manifolds. The crank case has a serial that traces to an 83"ci engine but from what I understand the top end and case must have been converted down to a 73"ci otherwise the additional stroke of the 83"ci would smash valves on the 73"ci heads. In order to correct it needs a new top-end, and if i'm gonna do that I'd rather rebuild it as the 83"ci it is supposed to be. I have a hard time imagining anyone would ever do something like this. Has anyone ever run into anything like this? Any suggestions?

 

The stroke has nothing to do with the heads but your right some one changed the head. The '81 head has a raised floor in the exhaust port for better flow so you need to find another '81 to '83 year head. You can find them through V-Twin. if your bike is a 1981 then it is 80 ci and the pistons are 80ci pistons which will not hit the valves in the 'o' ring head....if you had 74' pistons in there they would hit both heads so yourok in that dept. The aftermarket shops used to sell a plastic ringadapter to fill in the '0' ring groove so you could run the rubber band manifold seals.Your bike will run with the mismatched heads, I doubt you will feel a difference with a new head as long as you seal the manifold. The valves are the same size...the valve guides are a bit different andthe floorof the exh port is different thats all.

 

I rebuild a lot of engines earily and late and I always convert the heads and the manifold back to o-ring because they rarely ever leak.

 

Thanks for the info, helps a bunch.