[TR] Re GT6

[jimmuller at rcn.com]

Sam wrote:
> I understand the pricipals of the retard and realise that
> it does nothing off - idle.? The engine just doesn't rev
> as it should.

Here's the possibility.  Suppose your "retard" isn't, maybe because it is leaking or becaue it is stuck or because the port on the carb really isn't the right one for at-idle retard (due to DPO "re-arrangement"), or whatever.  If you set the timing as spec'ed for when it is operating properly, the timing will be at least 10 degrees too late.  Acceleration will be, umm (yawn), err, a bit oh I don't know, maybe (yawn) leisurely.

So here's a procedure to try.  If you little patience, then just jump to the last paragraph below.

Put a timing light on it, make sure it is idling at a reaonable slow speed, then pull the air tube off the vacuum unit.  This *should* do two things, introduce an air leak and make the timing jump forward about 10 deg.  What happens and what you do next will depend on what the engine does.

If nothing at all changes in the idle and the timing doesn't move, then your retard unit isn't working.  The likely reason is that the diaphram or the air tube is split; you know this because you just introduced an air leak and it made no difference.  Seal off the end of the air tube with your finger and see if anything changes.  If the diaphram is split but the air tube is okay, that should seal the air leak and at least do something to the idle.  (Whether it helps or hurts may depend on how well other things like mixture and timing are set or whether someone has already mis-set them to compensate for the problem.)

So back the question of what happens when you pulled the air tube off the vacuum unit.  It could be (though I'd say it is unlikely) that the retard unit is stuck, perhaps within the dizzy, but the diaphram and air tube are okay.  If so then pulling that tube *should* have introduced a leak and made the idle change at least a little.  You really don't want to run with that air leak.  Plug it if necessary, reset the mixture if necessary before judging the performance.

The real question is what your timing is with the retard unit's air tube attached vs. detached.  It should be about 8deg BTDC if the retard unit is non-functional, and 4deg ATDC with it functional.  I'm pulling these timing figures from memory so they may be a bit off.  But the transition between low single-digits After and upwards of 10 Before TDC should be unambiguous.  So just set the timing to match whatever state your retard unit actually is.
--
Jim Muller