Faltering '76 308

Have just replaced all 8 plug extenders and now have all cylinders firing. What a joy that is! One was short circuit, one completely open (>1MOhm) and the other six about 18k. The new ones are all about 2k.

Having done about 100 miles yesterday, the engine started to falter, like a loose connection in the primary side of the ignition. I'm reasonably sure its not fuel related as seems like its a complete momentary cut rather than a single cylinder. As far as I can tell, all the low voltage and HT connections are clean and tight but I may need to investigate more.

I've not been inside the distributor yet but note that there are two capacitors on the dissy and one each on the two coils. The car is 28 years old so do the capacitors routinely go intermittant after all that time?

Does the dissy run on points and do these go or need adjusting for clearance gap? We have a genuine 9,500 miles on the clock from new.

 

I'm surprised that you still have points in your car. A lot of us have changed to pointless setups. But if you still have them you need to check for gap and pitting on the points . Also before I converted my 77 I ran into a problem where the point head came loose and fired intermittently. Also with a point system I found that the plugs would foul at about 8-10k miles. Next would be the rotor and cap contacts make sure they are clean and not burned or pitted. And last is the extenders which I am surprised would be bad at 9500 miles unless they went with age. I believe that the earlier cars used the black extenders and not the red ones. I think that the black are not resistor types so there should be no resistance. Last is the wires which if they are carbon filled may be intermittent contact in the dist. cap. They also may be to dryed out from age and may need to be changed with new. Check resistance from the inside of the cap to the end of the extender.

 

There are two capacitors on your distributor because there are two sets of primary points inside (one for each bank and each coil) operating on a 4-lobe cam rather than just 1 point set operating on an 8-lobe cam.

Can't say that "failing capacitors" has been a commonly reported problem here (and would be a really lucky fix), but things like age, long-term moisture exposure (if any) would be negative influences.

As Steve K. suggested, it wouldn't hurt to first have a quick look under the cap (while measuring the contact-to-end wire resistances) and ensure that the points are opening/closing quasi-reasonably when the crankshaft is rotated by hand (the "open" mechanical physical gap spec should shown in your OM if you're not equipped to measure the electrical dwell) and that it's not full of oil .

 

The "condensors" in an ignition points system protect against arcing across the points during opening and closing. Capacitors are considered only good for 20-25 years in normal circuits, but I doubt yours are original, as you usually replace ignition condensors with the points, every 15K miles or less.

But if your condensors are gone, it means that you'll see burn spots on the points (signs of arcing) and you might not be getting a clean contact switching, leading to intermittant misfires on random cylinders of one bank.

I've also heard that breaker-point ignition systems don't really produce the kinds of voltage needed for platinum plugs. My experience is that my '79 Alfa (with points) does tend to get a lot of carbon on Bosch platinum plugs ... but my local mechanic insists on setting the Spica mixture a bit rich, which may have more to do with it than the Bosch vs Lodge plugs.

 

I would vote for point-less ignition system. Gone to it myself and that was one of the best updates ever for me. Crane is what I used.

 

Two Crane XR700 boxes with optical pickups. Set it and forget it. Starts every time and runs up to redline without skipping a beat! Conversion goes for about the same price as 4 sets of points.
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I have a question about the cranes. You replace the points with an optical device, right? But you still use the distributor? And what controls the advance at this point? The mechanical one that was used with the points or an electronic one in the crane?

Birdman

 

A shot of my 77 that has the Norwood conversion.

 

On the Crane's, the optical stuff and the electronics only replaces the point function -- the advance function is still provided by the mechanism(s) inside the distributor body/bodies (dependent on if you put 2 pick-ups in one distributor or 1 in each, respectively)

 

Dave,
What is the Norwood conversion? Obviously it's a single distributor, but what else can you tell me?

Thanks

Birdman

 

Single dizzy, electronic ignition.
with blaster coil, MSD box.
Uses inexpensive cap & rotor.
Speedo need to be sent to Palo Alto Speedo for recal.

While I enjoy the conversion, I will probably go a different route when I rebuilt the motor, while preping for NOS.

 

Dave,
What ignition wires are you using. I like their looks.

 

Taylor.

 

Thanks, that was quick! Ant particular model number of Taylor?

 

I don't remember the model #.
I bought a couple sets of the angle ends,
then when I change the cap and rotor, the alternate wire set is already installed on the new cap.

 

That is ... asking too much. The box with the number is at home!
Any Taylor V8 wire set is pretty decent. Open up the box and make sure you have 8 wires that are long enough. You'll end up cutting them any way. I actually split the square rubber wire connectors at the plug ends and use the straight stock black connectors.

 

Thanks guys.