Gawd I Hate Points, Won't keep a tune Options

[bbrock]

Quick background. Engine is a rebuilt 2L with Elgin cam and Weber 40IDFs. I bought a Pertronix Ignitor 3 to avoid having to mess with points but I could only get it to work well with a NOS Bosch 050 distributor. It runs rough with a brand new Bosch clone SVDA and the OE dizzy. However, the engine runs best with the OE DVDA distributor so I'm running that with points.

The problem is that I've had to adjust dwell and timing 3 times in only 1,000 miles of driving. Each time the dwell creeps up until the engine starts spitting and farting and is a bit hard to start when warm. Readjusting the dwell and timing gets it running like a top again. So (IMG:style_emoticons/default/WTF.gif) Only thing I can think is that the phenolic block on the points is wearing crazy fast. I lubed the cam and block with high temp slicone grease and I can feel it is still on there. Did I just get a shitty set of points?

[Superhawk996]

(IMG:style_emoticons/default/headbang.gif) Man. This is crazy. (IMG:style_emoticons/default/idea.gif)

So OK on the coil resistance with internal ballast. No burning. Check.

How about the screws that hold in the points plate to the distributor body? All tight?

What I'd really love is to see it curved on an old fashion distributor curve machine and/or hook up an O-scope to it.

What a mystery! Right guy is on the case though! (IMG:style_emoticons/default/aktion035.gif)

One more thought -- do you have the spring in there that goes between the distributor drive shaft (in engine case) and the distributor body / drive cog itself? That spring helps pre-load the drive shaft gear to the crank gear. If not pre-loaded, you would get some random dwell variance depening on gear mesh. Really stretching on theories here . . . ..

[bbrock]

Really stretching on theories here . . . ..

Yes you are (IMG:style_emoticons/default/biggrin.gif)

I checked the dwell again this morning. It was 52 degrees. I had it set at 46 degrees before my long drive on Thursday so a 6 deg increase in dwell angle (decrease in points gap) in about 200 miles. Enough to change the timing enough it was starting to sputter again. I pulled the points and think I confirmed this is just a shitty quality of points. It's hard to tell in this pic, but it looks to me like the wear block is being ground away and there is a little glob of grease on the leading edge that looks to be infused with the same material the block is made of. Of course I don't have a fresh set of identical points to compare with to confirm that's what's happening, but it's the only thing that really makes sense. A consistent decrease in gap due to the block wearing away. I have a couple sets of Bosch points on the way.



While I had the points out and just for grins, I threw the Pertronix III back in because it occurred to me I had never tried it in combo with the Bosch blue coil. It fired right up and after redialing the timing, it idled smooth although fast. Here's a question. I couldn't read the dwell angle on the Pertronix with my old Craftsman analog dwell meter. Is that to be expected? Anyway, I got my hopes up and took it for a test drive. No joy. It started bucking like a mule driving at around 20 mph. Out on the pavement, it pulled smoothly up to 100 mph, but driving at normal highway cruising speeds, it would randomly cut out. It feels almost like the rev limiter is kicking in randomly but it doesn't do this with the 050 dizzy. In other words, same result as previous tests.

I put a little extra grease on the wear block and cam lobes and spent 40 minutes cussing the fiddle-farty adjustment getting the dwell back in spec. That should stay in good enough tune until the replacement points arrive.

Just to answer Phil's last questions - we already covered the plate to distributor screw and yes, it is tight. And yes, the spring in the top of the drive shaft is installed. That wouldn't explain the symptoms anyway because I haven't seen random changes in dwell, but rather, a steady increase in dwell until the timing is changed enough to cause the engine to start sputtering. A slipping adjustment screw or wear block being ground down would fit what I'm seeing. Burnt contact surfaces seem like they'd be more likely to increase gap and therefore decrease dwell angle but I suppose something funky could happen that would weld material in heaps on one or both contact surfaces. My contacts look nearly brand new. Just a pinpoint sized black dot in the center of each surface where the spark is jumping. Totally normal wear after 1,000 miles.

[Steve73]

I had a similar point fail (fall apart) on a long haul drive in my VW a few years back. Was only a few weeks old. Was bought from a mail order parts company that has slipped in cheap non bosh parts. I called them and they refused to admit the part was not Bosh.

I've had good luck with Auto Zone rotor, cap and points on VW. Don't know if any 914 crossover. May not be your go to source. But in a pinch in could save a road trip etc.