In a message dated 96-08-22 11:32:47 EDT, kevins@borris.khoros.unm.edu (Kevin
Sullivan) writes:
<< Hey, I'm convinced. 20 before at what rpm? With distributor vacuum
connected or disconnected?
<< I also want to check that my valve timing is right. My timing mark on the
pulley seems to be off a bit: something like five degrees, if I recall, from
TDC as determined by looking down the spark plug holes and at the valves
rocking. I know you can flip the timing chain gears to alter the timing by
less than a tooth, but how do you know when it's right? >>
20 BTDC at idle with the vacuum still connected. John twist has a good
philosophy -- keep it simple and do it the easy way. Once you figure out
where it runs good, just leave everything connected and check it with a
timing light. Next time you feel inclined to do it, you just spot the timing
light and twist it back to the same spot.
As I recall the in and out lumps on the cam are very nearly symetrical. When
the crank is at TDC on the exhaust stroke, the out valve is closing and the
in valve is opening and they are both at the same height. If you want to
tinker with the cam timing, flipping the cam gear is probably too coarse and
too large a change. You might think about an adjustable cam sprocket for
just a couple of degrees.
For timing the valves, bring the #1 piston to TDC. With the spark plug out,
a small screw driver touching the piston through the spark plug hole, and a
wrench on the crankshaft, rock the crank back and forth a bit while you feel
the piston rise and fall. It's surprisingly easy to hit TDC within 1 degree.
Then check the valves on #1 or #3 cylinder (whichever are open) to verify
that they are open about the same amount, indicating that the cam timing is
correct.
Then, without moving the crankshaft, check for the timing mark on the
crankshaft pulley. It should be very near the 0 mark. If not near 0, the
harmonic balancer may have slipped (very nasty situation). If the balancer
outter ring has slipped relative to the inner hub, there is a good chance it
may slip again, possibly slipping off of the hub while running with very
undesireable consequences. I believe the rubber bit between the balancer
outter ring and the inner hub is supposed to be moulded in place, as in
vulcanized to both parts so it cannot slip. A slip means it should be
replaced ASAP.
I have heard that some crank shaft pulleys may have the timing mark in the
wrong place. IMHO this would probably not be from the factory but from some
PO swapping parts from different engines, the position of timing marks and
pointers varying somewhat on different models. If your timing mark is not
where it should be, you can make a new mark by filing or grinding a groove in
the right place. A touch of white paint in, on or over the new mark is
helpful when the timing light is used. Just remember that a new timing mark
is not a cure for a slipping balancer ring.
Barney Gaylord -- 1958 MGA
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