[Zmagnette] Timing

[Allen Bachelder]

D*mn iphone! You type in a word it doesn't recognize, or an outright typo and it makes up a word that might look a little like it.  A "chanson" is a French art song, not a timing device. I meant "timing CHAIN"!  And of course spellchecker doesn't help when you type "wondering" when you mean "wandering"!!

So, my timing wonders because I have a worn chanson.  I'm starting to wonder about myself!  Will wonders never cease...

A further bit of explanatory trivia for those seeking more unintended humorous effect from another Bachelder malaprop:  while I haven't set MG points in a good many years, I recall that the points gap is .015".  That means that if there is .015" of slop in the spindle bushing, the wobble will be enough to open points when they are supposed to be closed or close them when they are supposed to be open. That can and does lead to an erratic spark, and therefore an engine that runs erratically  ("crappy").  Pertronix doesn't rely on cam-induced physical opening and closing. It simply triggers the spark when the metallic strip on the spindle collar rotates in an out of the magnetic ("Magnettic"?) field of the sensor. These processes in and of themselves have nothing to do with timing.  They neither affect it nor are they affected by it. 

A loose timing chain (caused by a stretching chain and/or a worn tensioner) of course affects the synchronicity of the cam with the pistons, and the dizzy is driven off the cam.  That does affect timing, although the "wandering" of which I speak is usually observed while viewing the timing marks in the timing light.  But if the timing is set while the engine is cold, and it is later (4 months or 4 hours) observed  to be off when at full temperature, this could possibly explain it.   A chain might stretch a little with added heat.

Another unlikely cause might be worth considering.  Suppose your dizzy spindle is not keyed in correctly to the drive-gear pinion.  If it's not keyed in but pushed in firmly - in the wrong position, you might end up with only a friction drive to the dizzy spindle.  It could still be timed and made to run, but it would most likely slip periodically, creating the need to reset the timing frequently.  The punch line is to check and make sure the spindle is properly engaged. There's only one correct way to seat it.

I have a pet peeve about another concern that seems to be floating in and out of this thread. It's like which alternative are you going to use: Pertronix OR Schlemmerizing.  That's like asking: "Which do you prefer: Fram oil filters OR Goodyear tires?" The choice to "Schlemmerize" a dizzy has absolutely nothing to do with the spark triggering system. You can have Jeff Schlemmer rebuild your dizzy and then use points, Crane-Allison, or Pertronix. These are not mutually exclusive.  In my '73 B/GT, I run a Schlemmerized dizzy with Pertronix (instead of Petronix) AND an MSD 6A control.  It's always fast enough to put a smile on my face. Every 3,000 miles I squirt a little oil in the hole under the rotor. Outside of that, I can't remember when I last set the timing or performed any other service on my ignition system.  I've never had a Pertronix or MSD failure, BTW. ' Don't think I'll ever have the problem Perkins mentions - low voltage at the coil primary - as the MSD delivers about 90 volts to the coil primary. 

"Geraldine" has a Crane-Allison EI, and I know Jeff has a preference for these light-triggered systems.  I'm cautious because I have had two Crane-Allison failures in other MGs.  Of course in all cars, I carry a spare breaker plate with a set of points and condenser ready to go. 

Actually, I was probably one of the last converts to EI, since John Twist used to say they are "pointless".  I don't know if he still subscribes to that or not.

FWIW,
Allen

****************************************************************
Allen & Florrie Bachelder       =iii=<
Spring Creek Home for Wayward MGs
'57 ZB, '65 B, '69 C/GT, '73 B/GT
North Street, MI 48049, USA
http://www.mgexperience.net/member/bachldrs
****************************************************************

On Feb 6, 2014, at 5:51 PM, Allen Bachelder wrote:

> I should have added that the worn spindle bush will cause the crappy running (random missing, backfiring, etc) with points - but with Pertronix it would probably run fine. Often that's the way worn bushings were "fixed". Actually nothing is fixed that way - the spindle still wobbles but Pertronix just doesn't care. I suppose if the bush wears badly enough, the rotor might collide with some part of the cap. Not good!
> 
> Cheers. 
> Allen
> 
> Sent from my iPhone
> Spring Creek Home for Wayward MGs
> Allen Bachelder, prop. 
> 
> On Feb 6, 2014, at 5:37 PM, Allen Bachelder <bachldrs at comcast.net> wrote:
> 
>> I too vote heavily in favor of Schlemmerizing. I'm using Pertronics also. But if your timing is wondering it could be a sign of a loose timing chanson. Check your dizzy for sticking  vacuum &/or centrifugal advances first (easier fix!). 
>> 
>> Worn/wobbling dizzy spindle bush will cause it to run crappy all the time. Resetting the timing wouldn't help. 
>> 
>> FWIW. 
>> Allen
>> 
>> Sent from my iPhone
>> Spring Creek Home for Wayward MGs
>> Allen Bachelder, prop. 
>> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/zmagnette/attachments/20140207/38da3184/attachment-0001.html>