John---Valves that are "on the rock" I take to mean that both valves (on
any one cylinder) are off their seat an equal amount. i.e. When #6
intake and exhaust valves are at the same height, #1 piston should be at
TDC, and the cam is in perfect time. A more detailed explanation can be
found in the Bentley or TR6 Repair Manual, under "timing of the
camshaft".
Again, if your problem started as a result of an engine rebuild, check
the cam timing. If the problem you're having is not related to such a
rebuild, look elsewhere. Cams do not go out of time (very far) during
normal engine wear.
The distributor's centrifugal advance springs should have one 'slack'
spring and one under very slight tension when at rest. I cannot
recommend that these be fitted with anything but the stock springs. Is
this what you have?
When advancing the timing at idle from 12 deg. to 32 deg. the engine
speed should increase noticeably, as much as 200 rpm. Does it? When
setting the timing at 32 deg. at idle, the spark advance will be
dangerously high when the timing is "all in". As much as 50 deg. BTDC,
if your pulley marks could read this high.
Sugggestion:
While holding your timing light at the pulley, increase speed to get to
the point where the misfire takes place. Does the light blinking stay
consistant, indicating that the spark to #1 plug doesn't falter? Try the
same test with the timing light pickup on the other 5 wires. This will
test if the spark source is reliable.
That's all I can offer for now.
Dick T.
|