Triumph Repair: late 1973 GT6 III cam timing, degree wheel, compression stroke

Question
When setting up the top end to receive new cam timing sprocket and chain, should
#1 cyl be at TDC compression or at "point of balance" as described in factory
workshop manual.  The text implies "point of balance," while the illustration caption
suggests TDC compression stroke.

On my machine, the cam keyway is at 10:30 o'clock with Cyl #1 at point of balance,
and cyl #6 at TDC compression.  (Or does it even matter, as long as the distributor
knows when to fire?)

I really want to get this right the first time, but do not know how to use a degree
wheel.  My sense of precision in watching the valve train is based on lots of
experience adjusting the the valves, but no experience in competition fine-tuning
cams.  This is for simple street use.

Thanks for any time you need to answer, and for any help you can provide.  --
Orloff

Answer
It took me some time to figure this out, too;

What a degree wheel allows you to do is make an accurate estimate of where in the rotation of the engine is this point of balance or top dead center.  It is nearly impossible to measure the real TDC of the engine and cam lob using a dial indicator alone.  A degree wheel allows you to make a measurement on the rise of the cam lobe, and the trail of the cam lobe, and by taking the average (rise + fall)/2 = TDC for the cam lobe

It is the relationship of the crankshaft position to the cam lifting the intake valve that you are seeking to set.  The degree wheel allows you to set the crankshaft/cam relationship based on the grind of the cam.  there is a "centerline" cam setting of say, 106, that you are looking to set, where 106 is the TDC for the intake lob in relation to the rise & fall of the #1 cylinder.  By using the degree wheel in combination with dial indicator, you make estimations on the position for the cam lobe' "TDC", and adjust the cam gears, repeatedly, until you get the desired reading.

There are better technical articles on line that can give you more detail than I can in an email or posting.   It takes some trial and error and repeated attempts to learn how to set.  Be patient and you'll get it.  Reading up on the theory of cams may help, too.

http://www.boyleworks.com/ta400/psp/camshaft.html

http://www.youtube.com/watch?v=la6-EgnCOl4

http://www.popularhotrodding.com/enginemasters/articles/hardcore/0607em_high_per...