Hi all,
After all this time saying that things move at a glacial pace in my garage
(they do...), I (or rather *we*, as my Dad was here helping me) have made some
real progress.
For starters, let's talk about valve timing. My Bentley manual says (for the
stock cam):
intake valve opens at 18* BTDC and closes at 58* ABDC
exhaust valve opens at 58* BBDC and closes at 18* ATDC
So we made the assumption that the "39/76 76/39" numbers on my Kent Cams data
sheet are also:
intake valve opens at 39* BTDC and closes at 76* ABDC
exhaust valve opens at 76* BBDC and closes at 39* ATDC
With this in mind, we first figured that if the exhaust valve opens at 76*
BBDC, this equates to 104* ATDC. So we looked for the exhaust valve (with a
dial indicator on the #1 exhaust valve rocker arm - above the pushrod, not the
valve) to start opening at 104* ATDC. It opened around 75-76* ATDC. Off by
about 30*. Is this making sense so far??
With that new found information, and knowing that the crank turns twice for
every one rev of the cam shaft, we then figured that the cam was off by about
15*, which we figured was about 2 teeth on the sprocket, or one link in the
chain.
And, since the valve seemed to be opening *TOO SOON*, we further figured that
we'd have to rotate the cam *COUNTER*-clockwise to get it to open later in the
rotation. Is this correct??
So we marked the cam sprocket, the chain, and the relationship of the chain to
the crankshaft gear and proceeded to turn the cam back by 2 teeth/one link.
Then we reattached the chain cover and put the pulley on w/ the degree wheel.
When we rotated the engine - hoping to see the exhaust valve open around 104*
ATDC - what we actually found was that it began its opening at about 60* ATDC.
Exactly *OPPOSITE* of what we expected! Can anyone shed any light here?
We think we have two options - follow the set-up procedure in the Bentley
manual (which I'm not entirely comfortable with - unsure that we can keep the
cam from moving as we reassemble the sprocket/chain) or simply put the crank at
104* ATDC and rotate the cam to where the exhaust valve is just opening and
reassemble the sprocket/chain (same concerns here, though). Ok, a third option
is to push the cam forward again (to where it started, and then beyond) to see
what happens, but this makes so little sense in my mind: a) I can't see it
working; and 2. if it *did* work, I'll be even more puzzled. Oh, and it will
take up a lot of time....
Any insight/intel would be most welcome and appreciated. I hope all this makes
sense.
But if nothing else, I do know that my valve timing was way off - so I guess
that's the "real progress"!
--
George P.
Ruther Glen, VA
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