dwell, just a comment Options

[rhodyguy]

on the first initial runs the car displayed an annoying, not bad, but annoying, burble near back firing on decel at speed. rechecked dwell. it was high. regaped points. burble went right away and the idle was much smoother. this check with a tach/dwell takes about 30 seconds. when i see postings regarding backfiring, this will allways come to mind.

kevin

[VegasRacer]

Trouble-shooting 101.
Simple things first.

[Anton]

rechecked dwell. it was high. regapped points. burble went right away and the idle was much smoother.

How high?

Adjusting the dwell to a lower value will advance ignition timing. Or have you readjusted ignition timing after changing dwell?

I am having backfire trouble as well; adjusted to a leaner mixture (one full clockwise turn of the CO screw); it became much less.

[rhodyguy]

anton, i'm running webers w/ an 009, and triad. so i don't know if this is applicable to your situation. but i think it was near the 58 deg level, at wear limit as per hanyes. i went down to about 46. something was wrong, i checked it, the wrong went away. absolute timming is still to be check. the wife doesn't care for sitting in the car, reving it up, while in the garage.

kevin

[tryan]

.001 in change in point gap will change the timming 2-3 degrees. do you just set mat advance with an 09?

[Anton]

Thanks Kevin, 58 deg is way too much; I have something like 48 deg.

What probably has happened is that your points have worn off and dwell increased accordingly. It is not unlikely that dwell will soon increase again as the cause has not been addressed, i.e., worn condenser, distributor axis play, or just burned contacts/worn off nodge.

Perhaps you should repeat the procedure with new points AND condenser? (IMG:style_emoticons/default/smash.gif)

Oh, and a Bosch 009 distributor does not have enough advance for a 914; it is more suited for Bugs (type 1 and 3 engines). It is much better to use a (Brazilian) Bosch 050 distributor for Porsche engines.

Have fun! (IMG:style_emoticons/default/beer.gif)

[rhodyguy]

anton, i'm aware of the limitations of the 009. you must have missed the picture and the related nightmare of the NEW compufire that was junk. i put new points and conden. it was just my initial setup that was off. i went to thomlinson's weber book. i new my carb setup was close and that it had to be something else. i started with the easiest. my birthday was in june, anybody that wants to buy me a mallory and install it as a belated gift can feel free.

on the compufire, out of warrenty and no return on installed electrical parts. the implication being that i hooked the 2 f-in wires up wrong and made the solder run out of the one insulated wire. 98% of their returns on this item are owner installs, they RARELY have problems, blah blah blah . i told the prick that i didn't want the lecture and that perhaps i was the other 2%. asked him one more time if he would work with me on the issue. no way. i took the low road. let him know i would be contacting the credit card co to disallow the claim. "well you leave no options other than to sue for payment". "fine, would you like my attorneys name and phone #?, if you want the BIG hassle over your puny profit margin be my guest. serve me with intent." . the upside was the federal way police didn't have to be called. i guess getting to be a bit older has its bennefits.

kevin

[RustyWa]

Kevin, did you buy the Compufire locally?

[Anton]

Kevin, that story sucks. (IMG:style_emoticons/default/ar15.gif) Sorry to hear that. Luckily your 914 is now up and running.

Are OEM points/condenser combined with a Jacobs Coil (or an equivalent high output coil) an option? Or a new Bosch blue coil?

IMHO the advantages of electronic ignition over the standard ignition are marginal, unless you have cold (winter) conditions. Electronic ignition is supposed to be maintenance free (with a Hall or optical sensor instead of points). Inadequate maintenance of the standard ignition is more likely the problem for many classic car owners.

Multiple-spark electronic ignition would produce some (small) gain in torque/power, but the whole engine set-up must be optimal from the start to make it noticeable.

Other suggestions: I have seen people using the electronic ignition from a VW Bus type 4 engine with good result; will require modifications on the distributor or a complete exchange. (IMG:style_emoticons/default/smash.gif) Something to get from a wrecking yard; don't forget to get the wiring as well.

Good luck, Anton

[rhodyguy]

eric, it was ovals. they have a monopoly on a.m. parts in the south end. how was the trip?

anton, just the stock points, con, and coil. it works ok at this point. i stayed pretty close to the budget i set up for myself on this project. i didn't get wild with high end parts.

kevin

[RustyWa]

Trip was about a week too long. It's good to be home. Got in the teener the next day after I got back and drove it all around. It welcomed me home by having a stumble at a specific spot in the upper throttle as I accelerate. I'm guessing the TPS. I still need to investigate a little.

[need4speed]

In the past, I've set my dwell using a dwell meter/tach - but I was told that those things can be wildly inaccurate, and I should not rely on them, so I've been setting my points with a feeler gauge to .016.

1. Is it true that feeler gauge is a better method for setting points? Or should I be using my dwell meter?

2. What's the theory behind how dwell affects the way an engine runs? Wider gap means lower degree measurement - (right?) - which means. . . what, shorter duration spark, right?

[Anton]

Kevin, your story on dwell angle left me uneasy.

Although I installed new breaker points some months ago (at dwell angle 50 deg) and readjusted ignition timing with a strobe light, I rechecked today. Guess what; 52 deg. dwell angle. Readjusted to 48 deg as the normal value is 47+or- 3 deg. Idle immediately became better. To late for a test drive now; tomorrow is another day.

In response to need4speed:

1. No. Yes. Feeler gauge is used for the initial set up. Sometimes it happens to be the correct dwell angle, but's that more luck than wisdom.

2. Has to do with charging the condenser when the points open (are parallel), leading to a current through the primary circuit of the coil. That yields a high voltage on the secondary circuit and eventually a spark. So it's vice versa; wider gap, longer spark.