A Different Question About Points.
 

Since I'm lazy (sorry, Gunter) I've always set my points w/ a dwell of 35 to start, let them gradually get to 41 or so, and then replaced them. These are, of course, the extremes of the factory spec for the Bosch diz. Since w/ the CDI timing doesn't change as the dwell changes, this is no big deal.

Since I've always just changed my points @ 41, I don't even know if there is enough meat left on the rub block to go back and reset the points lower. There is obviously some material still there, but how much?

Does anyone know from experience whether there still is enough material left there to reset the points to the lower spec, thereby extending the service life of the points? Obviously this is moot if there are other issues, such as burning or transfer.

Timing does change as the rubbing block wears. This is just such a PITA to do why don't you stick to your same routine? Are you putting the bosch grease behind the rubbing block?

RS,

Now I'm confused. I had always thought that changing dwell changes timing (as you said) retarding it as the block wears down.

However, I thought that I have read on this forum that in fact this does not happen w/ CDI cars, since the CDI fires so frequently.

I wonder if someone else can chime in w/ a definitive answer on this.

And yes, I use the supplied grease.

until i see data showing that the the dwell (gap) makes any difference, i just eye ball mine and set the timing. in fact, my points have around 40k miles on them.

here is how i look at it.
the points are just a switch that opens and closes connecting ground to the CD unit, so very very low current, unlike conventional points cars. so the contacts dont wear.
as long as the points open enough to remove ground, and stay closed long enough to allow the cap in the CD unit to charge at high RPM, why sweat the small stuff.

you would have to get the dwell dead balls on to not change the timing, how ever small it may be. set the points, then just set the timing, or, just set the timing as the points wear.

Ty,

So you have noticed the timing change throughout the life of the points as they wear?

Since you keep the points in so long, how often do you change the timing, and how much of a change do you notice?

i dont really mess with it unless i have to. although i would be curious to know how much the timing would change due to wear.
there is another thread on this that i have seen. that info may be in that thread, cant remember.

the last time i messed with the timing was to run tests on timing and engine temps.

more of my off the wall thinking: (perhaps a bit of lazy too)
unless the timing is set on a dyno, no one really knows for sure if their timing is set to optimum for their car. so if the timing changes 1 or 2 degrees, is there any performance loss?

I thought I had seen something on this too, but I've been unable to come up w/ anything via searches.

I have seen everything from 1 degree of retardation per degree of point wear, 1/2 degree per degree of wear and no change at all in various writeups about CDI ignitions.

AFA a 1 or 2 degree timing change making a difference, there probably is a difference, but would you notice it? Hell, w/ no lambda on my car, the engine performs differently based on temperature and humidity variations so who knows if you would even pick up a gradual decline as the points wore down?

I have PMed Peter Zimmermann and John Walker to see if they can set the record straight on this.

I have heard back from Peter. He verified that the timing indeed does retard degree for degree as the points wear, even on CDI engines.

He also recommended that I do as I have always done--set the points initially to 35 and let them close down to 41 and then change them.

I'll try to do a butt dyno to see if I can notice any change while the timing retards, and, if the points are otherwise good, I may try resetting them to 35 (or as close as I can) once they wear down to 41.

butt dyno is huge from memory. Throttle response is noticable best right after points and timing are properly set and gradually goes away over time.

Best solution is a breakerless (Petronics) ignition. Just a single wire and always perfect.

Chris
73 911 E

i like my points. no electronics to go bad.

Can't argue w/ Chris there, especially now that we've verified the timing change.

Trouble is I have probably 8 unused sets of points--enough to last me the next 20-25 years!

I used to play this points game with my 2.7 MFI engine and then I installed a Pertronix setup. I check the timing every once in a while but it hardly changes.

I have heard that the timing varies cylinder to cylinder with Pertronix, but I have never been able to measure it myself.

It does spoil the fun if you love to check dwell!!