Cylinder head casting differences

[rpr851r]

Hello All,
I am working on my brothers 1966 CB77 motor. Unfortunately the head has a couple of broken fins and I would like to replace it for cosmetic reasons. I have 4 or 5 heads all with either broken fins, broken out exhaust stud holes, or welding. I do have one "perfect" head but it is a different casting. The one that was on the bike is in the first picture and has a " M" cast into it. The second picture is the best spare I have and has a "H3" cast into it. The question is either head correct for that year bike?
Thanks,
Rich

[LOUD MOUSE]

Mechanically they are the same.
Cosmetically (between the exhaust ports) they are different.
Parts book is difficult to determine the actual years as one they show ran from 62 to 67 but that's not correct as your second one was used long before 67.
The first one is the early issue and the second came along about 1965+-. ............lm

Hello All,
I am working on my brothers 1966 CB77 motor. Unfortunately the head has a couple of broken fins and I would like to replace it for cosmetic reasons. I have 4 or 5 heads all with either broken fins, broken out exhaust stud holes, or welding. I do have one "perfect" head but it is a different casting. The one that was on the bike is in the first picture and has a " M" cast into it. The second picture is the best spare I have and has a "H3" cast into it. The question is either head correct for that year bike?
Thanks,
Rich

[rpr851r]

Thanks a bunch LM,
It sounds like head #2 is in keeping with what may have been offered on that bike from the factory. I like to try and keep them as stock as possible but the history on the bike is sorted. It was crashed about 40 years ago literally into a swamp by my oldest brother. I remember to this day being in the basement with him and watching him pull mud from the top end as a 5 to 7 year old. The bike never ran right for him again and I am not sure if he swapped heads along the way or not. It sat in his collection for a long time and after he passed I resurrected the bike for another brother. Turns out that I think the entire reason the bike didn't run well was some home made throttle cables which never allowed the carbs to be consistently in sync. The bike was ridden off and on for the last few years but the motor was very tired (smoke, top end noise) and I am in the process of going through it. After disassembling and measuring it needs pistons, rings, bore, crank (little rod ends are sloppy) and a couple of trans parts AKA the usual.

Thanks again for the help,
Rich