Whats up with this scopes ignition pattern

Gosh, I haven't used a Sun Scope in years, I've forgotten most of what I ever knew, but I still have the 2nd edition of the "Sun Automotive Testing and Diagnosis" book. It looks like you have superimposed readings (due to the dual points?), your dwell angle is way too big (points set too tight?), and the firing lines for the #2 and #4 cylinders are much higher than on #1 and #3.

I've never worked on a 308, so my opinion may not count for much. This is one of the reasons that I opted for a 348 - I just didn't want to have to mess with distributors and carburetors.

 

Bill, I think that if I spent a few hours studying the threads on 308 ignition set-up, I might be able to help you, but at this point you probably know a whole lot more about it than I do. You're welcome to borrow the book (do you have instructions on using the machine?). Have you actually checked the dwell angle with a regular meter, or just set the points with a feeler gauge? I don't think the machine knows whether it is hooked up to a Pinto or a Ferrari, so you should be able to get a proper pattern out of it if it's hooked up correctly and the points/condensers/coils/plugs/etc. are OK.

Personally, I'd enjoy looking at it with you sometime. My schedule is pretty easy, send me a PM if you're interested.

 

Bill,
Is the car running badly, or are you just seeing bad patterns? I don't remember seeing anything like that, but I could never get a good tach reading on my Sun 1015 until I removed the R2 points completely.

Then I got rid of R1 points, replaced with dual Pertronix. Nice clean scope patterns now:
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cool !!!!

I HATE POINTS ............. ARG !

( mine are still hosed up..... )

 

I am not an expert on ignition, only what I have read and worked on over the years, but I had some issues with my car so I learned a bit about the early 308 points set-up out of necessity.

Was this with the car at normal idle with the micro switch for the R2 point made up? The long dwell angle would make since if this is the case. I understand that the way this works is that the mircoswitch grounds the R2 points effectively adding their dwell to that of the R1 points to retard the ignition 5 degrees at idle. This may help the coils develop enough energy to keep the plugs from fowling at idle as well. The wire that goes from the R2 condensers to the micro switch is shielded, but not very well from what I can see. I get some noise in my tach reading when the microswitch is made up (it jumps around about a hundred RPM or so). Disconnecting the R2 points is one option; however, I decided to make the stock set-up work properly. It does work fine if EVERYTHING is right.

 

If the microswitch is out of the circuit, I wonder why you are getting anything on the scope for the R2 points? The R2 points need to be electrically isolated from the distributor. The R2 condenser should be a two wire design with the ground lead connected to the microswitch. This was one problem with my car, the R2 condenser on the rear distributor was grounded to the R1 condenser, keeping the R2 points in the circuit all of the time. This made the engine lay down at high RPM.

I understand that you are going to go breakerless and I know that I am a dinosaur for staying with the breaker point system. I have a soft spot for older technology and appreciate how much was able to be done with so little. Ferrari stayed with breaker point ignitions for many years after most had gone to breakerless systems for a reason.

 

It's definitely not a drop-in deal, but you don't need a dist. machine either, if you have enough time. I had to design and have fabricated a mounting plate for the two Pertronix units (both in one dist.) and the magnetic collar needed some modification to fit. After that it was several iterations on the 'big dizzy machine' (the car) to get everything timed and synched correctly.

Even with the microswitch not activated, the presence of the extra condenser/wires/etc causes problems with the analyzer. You have to completely remove the R2 circuit in order to get the scope/tach to work properly. If you don't have to meet idle emissions then the R2 system is nothing more than an extra headache.

 

I may just pull my R2s out the next time I am in there then.

 

What was Pertronix kit type that was used to make the mod to eliminate points?

I am considering adding 4 Pertronix pick ups then using microswitch to switch between advance and retard pick ups. I want to make one distributor the advance set - 90 deg. pick up spacing and the second distributor the retard set. This will eliminate advance curve sync problems and allow retard at idle to still function. I don't know if the Pertronix pick ups can handle this sort of switching without distress.

Any guidance as to adapter plate fab would be appreciated. A Pertronix kit number would also be very helpful.

 

Looks like the scope is overlaying multiple ignition impulses on display. It is not possible to have multiple voltage traces in the same time domain. Scope in 4 cylinder mode? Coil primary and secondary pick ups on distributor being tested? Cylinder 1 pick up on distributor being tested (1 on rear distributor, 5 on front)?

Let me know if this helps or if I'm all wet.

Ken

 

I started with one of the Marelli kits, MR-142 or something like that, although by the time I had hacked them up I probably could have used any of the 4 cylinder kits.

 

What is the setup for the 4 connections - is a probe attached to each of four distributor outputs?
Where are you grounded?
Any capacitors in the circuits?

Thank you