Bouncing Tachometer Update!

Sunroof · 10-26-2001, 04:30 AM

Well..for those who jumped in a few days ago on what causes a tachometer to jump around, I finally solved the problem. I HAD NO GAP IN MY POINTS...nada, nothing!!!!!! No wonder the car ran like crap.

I reset the points to where they are supposed to be and like a miracle, the car runs great. One thing I do wonder about though is that the points only have 3k on them and that carbon fiber material that nests against the distributor cam arm is just about gone. How can that stuff wear down so fast? And, as it does, the gap changes. Does this mean I have to check the gap every few miles? The point contacts themselves were as clean as a whistle...interesting. Do I need more lubricate beyond what comes in that tiny bubble that comes along with the points? I have been advised not to over lubricate because the lubricant can sling around and disrupt the contactsd. Do I switch to the perma-tune unit that replaces the points forever?

Anyways, thanks Wayne and the rest of you guys for your input and helping me to solve a very annoying problem.

Bob
73.5 T

Jdub · 10-26-2001, 05:46 AM

Ahh points. How I love them! My SC has none, but I've been down this road many times with my MG/TR/Mercedes. Here is the old wisdom on points that has been handed down to me...I would be interested in anyone's comments.

The grease in the bubble is applied very sparingly. While it is designed to stick to the post, the stuff can fly off if you put too much on. Old points out, wipe down the post with a clean paper towel and electrical contact cleaner, and apply a smear to the post all around, removing the excess.

Use a dwell meter to set your points. Feeler gauges are ok, but setting by way of dwell is more accurate. Hook the meter up (coil post and engine ground usually), have someone turn the engine over (no it won't start; the cap is off and you've removed the fuel pump fuse...) and set the dwell via the adjusting slots of the points. Then start the car and check your work at idle. Readjust as needed now, before the points begin to wear,

Points wear "in". Set them to the low end of a setting (say 32 degrees where range is 32 to 36 as an example) so that, as they wear, they wear within the range. Never clean points with a file; only with a clean non-fibrous stiff paper, such as a company card. Never readjust points: throw them away and put in a new set instead. The idea is you set the spec to the high end and get many happy miles our of your points as they wear within range.

That's what I've been taught. Check your timing after setting the dwell if you are comfortable doing this.

Jw

EDIT: Got my dwell degree range advice straightened out: as points wear, they wear towards a larger dwell angle, which is the same as a smaller gap between the points.

[This message has been edited by Jdub (edited 10-26-2001).]

T Bird · 10-26-2001, 07:38 AM

Bob
It has been my experience that the fiber block on a set of new Bosch points will wear significantly in my 1972 "T" after as little as 600 miles. The first sign of this wear in my car is a reduced idle speed. As the points close up and the dwell angle increases, I believe that the timing retards, slowing the idle speed. I have experienced this rapid wear in spite of my use of Bosch distributor cam grease on the fiber block and distributor cam. The good news is that after re-adjusting the points at about the 500-600 mile mark, the fiber block seems to wear less and the timing holds longer.

Just my experience. If you don't have a tube of the Bosch grease, I'd recommend getting some. I believe I got mine from Stoddards. Go easy with it- you don't want it flying around the inside of the distributor.
John

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John
1972 911T Coupe
"S" pistons & Webers
PCA- Potomac Region

Jim Sims · 10-26-2001, 08:26 AM

The hardness/durability of the point arm follower is a compromise between wearing it out and wearing away the distributor lobe profile. It's better to wear out the points than the more expensive distributor. 3000 miles is a bit premature though; I've usually obtained 10,000 miles or so with other systems and I would think the CD system should do better. Are you using Bosch points! I'm told the other "store brands" don't work as well as the OEM parts. I was taught that it was okay to reset points as long as there wasn't a visible cone/crater on the contacts from metal being moved by the spark, but never clean the contacts. However, that was back in the days when labor was cheap and parts were expensive (hey wait, that sounds like my Porsche hobby today). I also adjust to the middle of the dwell specification range for best performance and then wear through the high dwell (gap too narrow) side of the tolerance range. I believe if you want to fully exploit the tolerance range for longest life given the way the Bosch point follower moves and wears (gap narrows as wear occurs) one should set at the lowest acceptable dwell (wide point gap). Correct me if I'm wrong here. Once in Mexico I set the points on a jeep using my finger nail; at first we thought it was the Pemex gas but it was just wear or the point lock screw becoming loose. By the way the points on my son's 73.5 have opposite hand to most other Porsche points. The wrong points were sent to me four times before I used information from one of Early_S_man's posts to tell the supplier exactly what to send! Cheers! Jim

Sunroof · 10-26-2001, 08:53 AM

Guys...
I just installed a new set of Bosch points a few minutes ago, set the dwell and reset the mixture and bingo, success!! What I learned is that I need to check the gap with greater frequency and carry a spare set of points onboard. This reminds me of my old Austin Healy and Triumph days when adjusting points was a way of life and part of the sports car ownership. Obviously, these older 911's share the same attention.

Now, I see Pelican Parts is offering the permatune system that installs in the cap rather then points. I have heard success with this cheap lifetime replacement and even performance enhancement. I for one am going to try it so I do not have worry about points again.....or at least midful of continuing adjustments. I believe this replacement is a direct screw in without having to remove the distributor.

Here's to the points club!!!!!

Regards
Bob
73.5 T

Early_S_Man · 10-26-2001, 09:21 AM

Bob,

The Perma-Tune doesn't replace your points ... just the CDI-unit! I strongly recommend that the distributor be removed, partly disassembled, and cleaned and lubricated every couple of years. If excess play or wobble is found between shaft and bushings, the bushings can be replaced with parts from an industrial bearing store.

The following thread has a generic Bosch exploded diagram of a distributor and specs for your distributor -- to check the advance curve before you have further running problems due to stuck advance weights:

http://www.pelicanparts.com/ultimate/Forum3/HTML/009677.html

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

Rot 911 · 10-26-2001, 10:06 AM

Warren, I wonder if Bob means the Pertronix unit that takes the place of points and not the Permatune CDI unit.

Kurt V
72 911E

fred hannah · 10-26-2001, 03:51 PM

kurt, i cant say for sure, but i think he had the name wrong. im thinking about doing the same thing. will i lose anything(other than points of course) by doing this change?

fred hannah · 10-26-2001, 03:53 PM

opps, posted on the wrong topic, sorry, disregard the above reply