Sanity check on dual points conversion

[z3beemer]

I've searched the forum on this topic but could not find exactly what I'm looking for. Here's the issue:  73 restoration.  Originally an auto trans with dual points.  I've converted to manual trans but I'm utilizing the original wiring harness.  All the pollution equipment has been removed.  The intake, carburetors, distributor, trans/clutch parts from a 72 have been installed.  Since the 72 dist. has only one points wire connection and the 73 had two, I've connected the two wires from the 73 wire harness together and connected them to the single connector on the 72 points.  Would this cause a problem?  The car starts ok and runs ok but is currently breaks up  after a few minutes driving and higher rpms.  Before I start more extensive troubleshooting to correct the issue, I want to eliminate the easy stuff first.  So, the questions are: connecting the two point wires from the dual system together and connecting them as one to the single contact point on the 72 distributor OK to do?  If not, which wire from the dual point harness should be connected to the distributor and which one should be disconnected? Your input is greatly appreciated.

[Yarb]

I’m not an expert nor have I attempted this before. My initial thought would be just to connect one wire and try that first. I’m sure you’ll find an answer here from someone that’s been down that road.

[SteveJ]

I'm not going to verify my sanity nor anyone else's.

This may help explain the erratic behavior.

From the EE section of the FSM: (Note what it says about the dual points.)

So when the engine comes up to temperature, the timing is retarded for the automatic transmissions.

Here's how it looks in the wiring diagram:

As @Yarb said, use one set of points. Tune to that. Be happy.

[Mark Maras]

I agree. Use one set of points. The plus side is you won't have to carry a spare set in the glove box.

[Captain Obvious]

If I understand correctly, your modification should work fine as is and I'm thinking your issues are not (directly) caused by the single point mod.

So on the 73 harness, there are two black wires that go to the distributor for the points, right? And you have shorted both of them together and then connected that pair to the single wire coming out of the 72 distributor? If that's the case, it should be fine.

But, stranger things have happened. Can you put the original 73 distributor back in just to see if the problem goes away?

[z3beemer]

Captain Obvious, your summary of my wiring is correct.  I was pretty sure my logic on how I connected it was correct, just wanted a second opinion.  Thanks.  I don't really think my current issue is ignition related.  I think it is more fuel related.  Maybe more carb tweaking.  I checked the plugs and 1-3 appear to be running rich, 3-6 appear to be more in the normal range.  Next I'll try leaning out the front carb and then rebalance.  Other possibility may be float adjustment but I think I was pretty accurate when I adjusted them.  I'll try the easy stuff first.

[Captain Obvious]

Yeah, if it's as simple as it sounds, it's likely that your wiring change is not what's causing the problem.

However... Note the word "directly" that I used earlier.   The reason I said that is because there may still be a problem with the 72 distributor you threw in there which is causing a problem. Points not set correctly. Dwell issue. Spark scatter from bushing wobble. Leaky condenser killing spark at higher RPM... Lots of problems could be caused by the distributor but might not be caused by the wiring modification you made. 

Point is, I'm not yet giving your 72 distributor a thumbs up, but I don't think the problem is your wiring change. Does that make sense?

[z3beemer]

I guess a mechanical issue with the 72 distributor is a possibility but points, cap rotor and condenser are all new (not that that's a guarantee they are good).  Points were set using a dwell meter , not a feeler gauge.  Other things that have me leaning toward fuel issue is that it only happens under load.  At idle I can run the rpm's up to several thousand rpms with no issue. Also, if it was ignition related it would be odd that it only affected cylinders 1-3 and not 4-6.  Another fact that may be contributing to the problem (but not sure it would), currently, I do not have the entire exhaust system installed, only the headers are installed.  Planned on taking it down to the exhaust shop to get it finished out once I got it running decent. I still have the 73 distributor if I want to swap it out, I was unaware until this post that you could run a dual point distributor and use it as a single point set up.   Thanks for the input.  I appreciate it.

[Mark Maras]

It will pull high RPMs under no load. What happens when it's under load? Does it start to miss intermittently or just run out of power and refuse to rev higher?

 While not ruling out electrical, I'm leaning (snort) towards it being a lack of fuel.

[Captain Obvious]

8 hours ago, z3beemer said:

I guess a mechanical issue with the 72 distributor is a possibility but points, cap rotor and condenser are all new (not that that's a guarantee they are good).  

Yeah, I'm not saying that's the problem, just tossing out ideas and possibilities. From the other stuff you mentioned, like differences between plug groups, it certainly sounds like it could be an issue elsewhere.

 Happy hunting, and hope you get it running the way you want it!  

[z3beemer]

Mark it seem to be ok when driving it initially and at low rpm but started breaking up as I increased speed and rpms.  It's  ok at high rpms when idling with no load.  This was the first shakedown ride so I need to do some more investigating.  I think the next thing I'll try is leaning out the front carb a little.  If that doesn't help maybe recheck float adjustments again.

[Yarb]

I’ve always asked folks here. Have you checked the coil?