Also beware of the 406 heads. There are 3 heads with the C3AE-C casting number on them. The true 406 heads will have real small chambers (some data says 56-61cc), 1.65" exhaust valves, and be cut for spring cups. The other 2 versions are 390 heads with standard 1.55" exhaust valves and no spring cups. The standard 390 head will have 72cc chambers, and the high altitude will have 68cc chambers.
The C3AE-C head was only used from mid December of 62 to the end of 406 production, which wasn't very much later. The 390 versions were used for the rest of the year on all 390s, and then in 64 the C4AE-G replaced it.
Trust me when I say that alot of people selling 63 406 heads don't know what they have. I've personally been burned twice by guys swearing they were 406 heads. The first time I didn't know any better, and the heads were bare. The second time they had been upgraded with CJ valves and spring cups, but were still 72cc chambers.
Of the multiple sets I've had, only 1 were real 406 heads and they were dated late Dec. Every other one I've seen was one of the 390 versions and were dated from Feb on, although I've also been told there were service heads after that.
First thing to check is the exhaust valve size if the heads are unmolested, and also for spring cups. If that looks good or they have been worked on before, the chamber volume has to be checked. Now if I'm looking for 406 heads I only will buy if the chamber volume has been checked.
