Hi all,
My latest dilemma started out as an ignition timing problem. The ignition is a
Mallory Dual point, so I no longer have the vernier scale as on the stock
distributor. I've marked the crank pulley so I can read the crankshaft degrees
with a timing light. I've always heard that conventional wisdom says to
advance the ignition at idle until the revs stop increasing, and then maybe
back it off slightly. The problem is that my engine seems to continue
responding to more and more idle advance up to almost 30 degrees. This seems
way out of line.
I checked the carbs, and they are synched and running at about 3.5% CO at the
tailpipe. Then I started wondering if I pulled a bonehead maneuver when I
installed the cam and got it all off. Set up the dial indicator and yep, sure
enough, it looks my intent to advance the cam by four degrees actually turned
into retarding the cam by four degrees. Much banging of forehead on wall.
I'll be pulling it apart tonight and resetting the cam.
My question is, would a retarded cam cause the engine to want more ignition
advance, or do I have something else going on? Other pertinent details are
that the cam is a 490 lift/280 duration with 20 degrees of overlap (these
numbers are NOT at 0.050 lift, so reality is somewhat less radical), there is
80 thou shaved off the head, intake valves are oversized, 87mm pistons,
combustion chambers redone as per Kastner with the liners eyebrowed. There
are other mods, but I think that is everything that would matter.
I'll buy a beer for the first one who can explain this (although this may
explain how the cam wound up retarded). My concern is that I may have
overcammed the engine and that this is the sort of ign advance I will have to
live with until I get a milder cam.
TIA,
David Rupert
1957 TR3
1967 TR4A
1980 TR7
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