[AMC-List] Continuing Saga of Doc the Jeep, Part II.5

[Nick Lenarz <n9viw@xxxxxxxxx>]

Some of you may recall the problem I've been having with my Jeep, under
the heading "Weird non-running issue, '82 Jeep CJ". Things are
better... sorta.
Replaced the intake and exhaust manifold gaskets today, and found that
my exhaust manifold is sprung along the X axis- a very slight vertical
bow, with the end cylinders (1 & 6) a bit (1/8") higher than the
middle. I found that the end cylinder ports were not 100% covered by
the gasket because of this, and there was a small exhaust leak at
cylinders 1, 2, and 6, right at the bottom of each port on the gasket.
The intake manifold ports were securely covered, though.
I was able to force the #1 cylinder down with a crowbar and tighten it
in place on the new gasket, and tightened the manifolds down in the
usual sequence. I started the engine up, and while the timing is still
way off (26+ degrees BTDC at idle), it runs well enough. I took it for
a spin around the block, and while it was peppy enough, it had a
disconcerting spark knock whenever I put the engine under moderate
load. I noted that yesterday, but attributed it to a manifold leak
causing a lean condition.
I took it home and completely disconnected the vacuum advance line and
took it out again, but it still has a spark knock when under load. I
had checked the mechanical weights yesterday, and found they were
moving freely and securely fastened.
One recent thought I have had regards cam timing- I know for certain
that the Comp Cams #252h is cut 4* advanced, but I seem to recall
installing the Cloyes timing set at 3* advanced as well. If this is the
case, I have 7* advanced valve timing.

<<<IMPORTANT PART>>>
The thing I need to know is, does anyone here know where I can find a
definitive documented connection between valve and spark timing, and
specifically changes of one affecting the other?
<<</IMPORTANT PART>>>

If my hypothesis is correct, the spark timing HAS to be advanced
(rather, is required to be) BECAUSE the valve timing is advanced, in
order to find that 'sweet spot' where combustion and vacuum is best.
That sweet spot, however, must then be that much narrower a crossover,
which would explain why I get the preignition (spark knock) on engine
load, but never did before I installed the cam gears.
I don't dare drive it like this, because at highway speeds I can't hear
the knock, and would worry about doing internal damage. Next weekend
I'm going to be out of town, but the following weekend (if enough
people suggest it) I think I will pull the timing cover and set the
gears back to 0* advanced (if it is, in fact, advanced at all).
Please, inundate me with your thoughts, concerns and suggestions! :D


 
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