my 70 TR6C.
I found the correct rocker boxes and also a head stamped 66. I have read that it was stamped with the year before the bike - meaning the 66 is really for a 67. Correct?
Mmmm ... when you say "stamped", you mean the cast date - year ("66") plus up to twelve short radial lines denoting the month(s)? Afaik, this is just a casting date, there isn't any 'rule' about how the raw casting was subsequently machined for a particular 'model year'.
Nevertheless, afaict not a huge problem:-
Info i have says: The basic idea that all 9 bolt heads will bolt to any 9-bolt cylinder is correct. However, the tappet guide blocks, pushrod tubes and cylinder heads MUST be matched completely.
So, this means I need to replace the current set up with a set from a 70 cylinder head - meaning tappet guide blocks, pushrod tubes?
Here, no. Having posted you likely have a '66 or '67 head, then "tappet guide blocks, pushrod tubes and cylinder heads MUST be matched completely
", why do you want "a set from a 70
cylinder head" ...? If
you have a '66 or '67 head, you want '66/'67
tappet blocks and prt (and 70-4746 "Bottom cup")?If
you have a '66 or '67 head, the only other difference is '67 notionally uses a thicker bottom seal (E4752) than '66 (E3547). However, in reality, they're both the same dimensions except E4752 is 1/8" thick while E3547 is only 1/10" thick (both nominal), you'll check the 'crush' and use what's required to get in the 'correct' range?