Home 1968 Shelby Cobra GT350, GT500 & GT500KR My 1968 Shelby Cobra GT350 Pertronix Pointless Ignition

Pertronix Pointless Ignition

I inherited a new chief mechanic, the prior owner of the shop that arranged for my engine to get a rebuild, retired the first of the year, leaving me with his partner, Eric. Turns out Eric was probably a better choice for my classic Ford Mustang. Although Eric happens to be a Chevy guy.

He and I have been sorting out things with my Mustang. The engine just isn’t running right yet. It is running much better but not wonderful. If that makes sense.

For the uninitiated, if you keep your car stock, as it left the factory, then you can look up the settings and specs in a book. These stock settings, like timing and carb idle, work fine for a stock engine.

However, my Mustang is not stock. (And yes, there is a lesson here.) My engine left stock the minute Dan, my engine builder, asked what do you want to do with this engine and I said let’s get some more horsepower out of it. We changed everything about this engine except the crankshaft, the block and the intake manifold. In hindsight, perhaps I went with a bit too radical camshaft but that is what I have.

So the trick to tuning an engine, that is no longer stock, is to be aware of the components added, then tweak the settings seeking the magic settings that the engine likes. Step one is to set the timing. The engine needs to fire the spark plugs at the optimum time for this engine to utilize this Comp cam. Will, the retired owner, set the timing to stock 8 degrees initial timing. This is not a stock engine, it didn’t run right and it ran too hot. Common symptoms that the timing is off.

We bumped the timing to 10 degrees. I took it for a turn around the block to see if that made any difference. Nope. We moved it to 12 degrees. A quick run around the block didn’t tell me that was correct. So we moved it to 14 degrees initial and 32 total advance. It ran much better. The difference was obvious. And it ran much cooler.

But during this process Eric told me the distributor I had on this engine was part of the problem. For one thing the timing wasn’t stable. You could see the timing changing up and down on the timing light. The shaft had some play in it plus the stop to hold the distributor cap in place was missing. He told me to not to bring my car back to him until I had gotten a new distributor. One of those things on my “don’t mess with it until it breaks” list. Eric said that old distributor was not going to maximize this engine. This distributor was also missing the vacuum advance. I looked up the numbers on it. Turns out my distributor came out of a ’67 2 barrel 289. That was the distributor in the car when I got it. Kind makes me wonder what happened to the original engine and parts.

I wanted to stay with an electronic pointless ignition. I had installed a Pertronix points removal upgrade back in the 80’s. It has been working flawlessly all those years. And there are no points to mess with. I did a Google search to see what was available. Eric recommended a MSD. That’s because he is a GM guy, but the MSD cap is GM red. I wanted a Ford look alike. Pertronix offered such a replacement. I put in the order. About a week later my new, beautiful distributor showed up. And yes, it looks just like a Ford distributor but unlike my old one, it is shiny and new. And the shaft did not wiggle.

I took my Mustang back to Eric and proudly showed him my new distributor. He quickly installed it. The difference was obvious. The timing stayed consistent. I had the wrong distributor anyway. It was a 1967 unit that came out of a 2 bbl engine with a missing vacuum advance. And the stop that holds the distributor cap in place was gone allowing the cap to move.

That is the good news. Now for a couple of “are you kidding me” issues:

Once you leave the world of stock parts, you need to sort out what happens if you make a change in parts. Here I go again.

Distributor Gear

So one of the first questions is what timing would work best for this distributor in this engine. I called Comp Cam for some advice. The Comp Cam guy very quickly asked what distributor I had purchased. Pertronix. Then he told me not to drive my car until I replaced the cam gear on that distributor. What? He said the gear that comes with this Pertronix unit is too hard and will wipe out the gear on the Comp cam. I asked him if it would be a bad idea to drive it to a car show coming up in a couple of days. He responses was pretty direct. “Don’t even start it up or drive it until you swap out that distributor gear.”

On the bottom of the Distributor is a gear that syncs up with the gear on the cam. The cam rotates which turns the distributor shaft. Those two gears not only need to match up, they also need to complement each other. Too hard of a distributor gear will wear or worse the cam gear. It is much preferable to wear the distributor gear than the cam gear. You can easily replace a distributor gear. Bad cam gear? Replace the cam. I did some research on the car forums and sure enough there are plenty of horror stories of the dizzy gear eating the cam gear. The worse part of that fiasco is where the pieces of the gear end up. In your oil. On the other side, I have a friend with a 64 Ford Fairlane. Real nice car. He has the same distributor and cam that I have. He has been driving his car for several years. After he told me about the parts and I shared the dizzy gear story I had been told, this was a complete surprise to him.

There were FOUR different distributor gears available from softer to very hard. New cars used harden gears. Old cars may not. Then there is the differences between manufacturers.

It turned out Comp Cams had a gear that worked with their cams. Cost me another $100 just for the gear. So my relatively inexpensive distributor just cost $100 more buying the proper gear.

I did look at a lot of forums and conversations from other car owners. Yep, there were numerous posts from owners that discovered too late the truth of running too hard of a gear on your distributor. Do metal shards floating through the engine sound like a good idea?

I did talk with Pertronix after ordering the gear. That rep told me Pertronix does not agree with that Comp cam statement. He said Pertronix buys the SAME Ford looking distributor from the SAME manufacturer that all the other distributors retailers offer. Pertronix just adds the electronics. The gear on the Pertronix unit is the same gear as on all the others. I did complain to Summit Racing where I got the Pertronix from. That fellow knew exactly what I was talking about and agreed that Summit should give the buyers of a distributor a choice of gears. I’m out another $100. But I have a very nice, brand new, billet aluminum distributor and this cool, useless distributor gear.

I got the new gear in the mail and took my Mustang back to Eric. He removed the distributor and the existing gear on the bottom. He then pressed my new recommended Comp Cams gear onto the distributor then reinstalled. And No, you couldn’t tell any difference other than some renewed confidence.

Bottom line my car needed a better distributor and runs much better.

Ported Vs Manifold Vacuum? (Which is Better) ?

As we were tuning my engine, Eric raised this question. Do I want the vacuum advance on my new distributor to run off the manifold vacuum or ported vacuum source? I didn’t realize this was even a question much less what the answer was.

After doing some research and with Eric’s advice, we ran it off the manifold. Click here for additional info and conversation about this particular point.

12 Volt VS 6 Volt

My car is running pretty good. There is something that is not right but I can’t put my finger on it. It might be the carb tune or something. So I am doing some reading and to my surprise I discover another ” Are you kidding me.”

Cars from the era are 12 volt systems. Much earlier cars were 6 volt. So that means if you test the positive at the battery you will get 12 volts.

But cars from this era all had points in the distributor. Those coils need 6 volt. Apparently, if you send 12 V to a 6V coil, it could explode. I am still working on whether this is an issue. My car seems to run ok. I have a new ignition switch pigtail to replace the faulty one in my car. I need the answer the to this 12 v 6v question before I replace this pigtail.

PerTronix Flame-Thrower Stock Look Cast Distributors D134600

Distributor, Flame-Thrower, Ignitor I, Stock Look, Magnetic Pickup, Vacuum Advance, Cap, Ford, V8,

PerTronix Flame-Thrower Stock Look Cast Distributors

Pertronix Flame-Thrower stock look cast distributors are loaded with all of the features that you would expect from a high performance part, and yet they maintain the original look, for the ultimate “sleeper.” Pertronix builds each distributor with all-new components, not from remanufactured parts like some companies do. No longer will you need to hassle with adjusting points or replacing capacitors, because these distributors are equipped with maintenance-free Ignitor electronics, providing decades of trouble-free operation. Each distributor is complete with a high-quality cap and rotor, so you’re ready to run right out of the box.

Stock look distributor features include:
* All-new lightweight cast aluminum housing, modeled after the original Delco and Motorcraft distributors
* Hardened gear ground to exact tolerances for precise mesh with cam
* Adjustable vacuum advance canister, providing extra tunability
* Optimized phasing to ensure maximum energy to the spark plug
* Tailored advance curve for optimal performance and drivability
* Integrated electronic ignition–available with solid-state Ignitor or the powerful Ignitor III with built-in adjustable REV limiter and multi-spark through redline
* High dielectric strength cap and rotor with brass contacts
* Legal in all 50 states and Canada (C.A.R.B. E.O. #D-57-23)

Brand: PerTronix

Manufacturer’s Part Number: D134600

Part Type: Distributors

Product Line: PerTronix Flame-Thrower Stock Look Cast Distributors

Summit Racing Part Number: PNX-D134600

UPC: 694342535964

Computer-Controlled Compatible: No

Trigger Style: Magnetic

Advance Type: Vacuum and mechanical

Ignition Box Required:No

Cap Style: Female/Socket

Mechanical Tach Drive: No

Slip Collar: No

Distributor Gear Material: Steel

Distributor Gear Rotation: Standard

Distributor Cap Color: Black

Housing Material: Cast aluminum

Housing Finish: Natural

Marine Use: No

Quantity: Sold individually.

Notes: Hardened steel gear is also compatible with billet roller camshafts.

CARB EO Number(s): D-57-23

Emissions: California EO Approved