Posted by Andy Z on 9/15/2007, 5:19 pm, in reply to "Re: ignition timing"
66.36.128.213
Thanks for your help, Glen. And also a very interesting post about cam timing, saved and printed for near-future use.
--Previous Message--
: Andy it's either one or the other type
: advance unit unless you have the
: dual control with 2 ports on the
: capsule, acting on either side of
: the diaphragm. In either case the
: vacuum line will only go to one
: carb, if it's an actual advance unit
: or dual control. The backasswards
: unit which retards under manifold
: vacuum, & loses it (advancing),
: obviously goes to a manifold port.
: I'm not sure exactly what unit you
: have.
: I can only guess that the diaphragm
: isn't moving because it's hard as a
: rock from age, it should obviously
: move freely when vacuum is applied.
: Honestly the inop vacuum advance
: should not affect driveability to
: the point that the car cant be
: driven normally.
: HTH
: Glen
:
:
: --Previous Message--
: My vacuum capsule is advance/retard.
: Stupid question: which connection
: goes on which carb?
:
: If I disconnect both lines and idle
: the engine, and hook up the pump,
: the timing does not advance (the
: plate does not rotate). I removed
: the capsule, and the plate does
: rotate. With the capsule still
: removed, a vacuum applied to it does
: not move the linkage rod. But the
: vacuum holds, so the diaphragm is
: OK. Then, I inserted a thin wire
: into the advance port, and pushed
: the linkage. The wire moved out, so
: the linkage is connectd to the
: diaphragm. Beats me.
:
: I have some spare springs, I can
: check the mech curve later. But my
: immediate concern is driveability,
: as in not stalling in intersections,
: which I assume the vacuum advance
: would help. But if I can't fix that,
: I'll have to advance the idle timing
: for now.
:
: Thanks
:
: Andy Z
:
: --Previous Message--
: If you hook up your vacuum pump
: (static) to the vacuum capsule,
: which way does it rotate the breaker
: plate, advance or retard? I'm
: assuming that it only has 1 port on
: the unit, one type fitted to the
: GT-6 had a combination
: advance/retard with 2 connections.
: In my previous post I should have
: added that the numbers I quoted are
: BTDC @ idle.
: Most counterweights are 14 degrees
: +/- in the distributor X 2 (cam half
: speed of crank), so you have about
: 28 degrees available mechanical, so
: idle is going to run somewhere 5-10
: degrees before.
: Before you come to a conclusion you
: should check the curve, &
: remember that the retarded retard @
: idle is emissions control related,
: don't sweat it.
: Glen
:
: --Previous Message--
: Thanks for the replies, Glen and
: John.
:
: The mechanical advance does work.
: Not sure how correctly, but it does
: work.
:
: What I can't figure out is why the
: vacuum advance does not work. I'm
: getting vacuum from the carb. If I
: connect a vacuun pump to the
: distributor advance inlet, I can get
: a vacuum reading (so no leak there),
: but no timing advance. I replaced
: the capsule with a good spare, no
: change. The distributor plate does
: rotate freely.
:
: As far as the crant/camshaft issue,
: I didn't touch the engine, but that
: is something I certainly feared.
:
: So, I guess I'll just run it at 10
: BTDC and hope that divine
: inspiration (or intervention?)
: provides a clue.
:
:
:
: --Previous Message--
: More important than initial idle
: setting is the actual curve
: including full advance. There are 2
: different types of vacuum controls.
: First is the traditional advance
: that advances slightly as vacuum
: increases. The other actually
: retards the timing using manifold
: vacuum, & when the throttle is
: opened & manifold vacuum
: decreases, it will allow the timing
: to advance. Vacuum controls are
: largely emmission control related
: anyhow...
: The real advance is mechanical &
: is controlled by spring loaded
: counterweights down under the
: breaker plate.
: Now what you need to do is first
: check & make sure that the
: vacuum control pipe is hooked up to
: the correct fitting, carb or
: manifold, depending what is fitted.
: Then run it up with a timing light
: on it & check it at 500 rpm
: increments up to 4k or so & get
: an idea what the curve is. Vacuum
: controls aside, most engines want
: 5-10 degrees @ idle & mid-30s
: full +/-.
: See how yours compares.
: Also if the cam/crank aren't timed
: properly, it will screw up the
: timing requirements but I don't want
: to go there unless we have to...
: HTH
: Glen
:
: --Previous Message--
: I've just put my 69 GT6+ on the road
: after a long and painful rebuild,
: and am having issues with (I
: think)the timing. The car is
: completely stock. Idle timing for an
: emmission-controlled GT6+ is 6deg
: ATDC. Basically, getting underway,
: the engine just tries to stall for a
: couple of seconds, then gets up
: enough courage to continue pulling.
: I checked the vacuum advance with a
: vacuum pump, and there seems to be
: effect on the timing with vacuum. If
: I advance the timing quite a bit
: (about 10-15 BTDC) the car seems to
: run much better. I would like to
: drive the car while I try to fix
: this problem, but am not sure if
: this will damage the engine. Any
: responses based on actual experience
: or well-intentioned opinion are
: equally welcome. Thanks.
:
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