Hi. I have a 1971 Triumph Bonneville engine that has the head missing from it. Are there other heads compatible with this engine. At the moment i am looking at a 1968 head and am wondering if that would fit.
My 2c is you may be better looking for a 71 or later head rather than an earlier one.
My 71 had a 1966 head on it. It worked but there were issues. I have now bought and reconditioned a 71 head to get around those issues.
The 71 has a very different frame to the earlier bikes and has a lot less room above the motor to fit bolts etc.
If you can fit 1971 or later head bolts to the older heads then it may be fine but if not you will not have much fun. Others will know if that is possible.
The problem is the older head bolts means to install the head bolts you have to remove all the engine mounting bolts so it is free in the frame and then you can rock the engine in the frame enough to squeeze the head bolts into place. Torquing the head is also near impossible without rocking the engine. I think you will also need to fabricate a custom head steady brace (although that isn't hard)
If the newer head bolts (1971 or later) can be made to fit the older head then that should resolve the above issues but I think the newer heads (1971 and later) and the later rocker boxes with larger access ports are probably better than pre 1971 versions for OIF frames like yours.
This depends on what type of frame you plan to put this engine into. If you plan to fit it into a '71 or later frame, you'll need a '71-onward head and you could use any rocker boxes made for '71 model or later. There were changes to the head in mid-'72 and they then used different exhaust pipes (push-in instead of push-over and clamped), and bolt on cast aluminium intake manifolds instead of a screwed in steel tube with a welded flange.
By '73, most Bonnevilles were 750 (different head), but they did a make a few 650 engines in '73 and '74. There were small changes to the 650 head between '72 and '74, a different aluminium intake manifold, and changes to valve spring collar thickness to suit casting thickness change under the collars.
The '68 head won't suit your pushrod tubes and tappet blocks, and would have to be used with pre-'71 rockerboxes, which won't suit a '71 onward frame. You could change the tappet blocks and pushrod tubes, but you'd still be stuck with pre-'71 rockerboxes.
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