GMC V-6 ignition question
 

I have a 63 GMC pickup with a 305, and have noticed there seems to be 2 types of distributors for this engine. Mine has the externally adjustable points (window like v-8 distributors). I think I have seen pictures of other 305s with distributor caps that resemble in line 6 type. Anyone know if there’s a year or model changeover point? Or am I mistaken?

Re: GMC V-6 ignition question
 

60-66 has window. Probably changed in 67 or late 66

Re: GMC V-6 ignition question
 

Post from the archives by Pete Chronis;

The other thing I'd like to bring up is the early distributor had the advance weights on top just like the V8 models and the housing was cast iron, the later small cap distributor housings were cast out of aluminum and the weights were mounted below the point and condenser plate. Right around 1964 the smaller distributor came in to supersede the big cap distributor though some larger series trucks and engines still used the big cap distributor through 1965.
Pete Chronis Northern Cal.

Re: GMC V-6 ignition question
 

This item is confusing because our own "known good parts" shows both types for the same year motors. Rockauto shows window up to 65-66.
Jolly shows two types of caps and two types of vac advance depending on the distributor weight design as Pete says. Parts are shown for same years 63-66. As Pete says, some motor had one way and some another.
This may conflict a little with Pete and I am not an expert but, sounds like early (60-62) caps were known as small cap and has clips to hold the cap on. Also the rotor was slip on with weights under plate. 63-65 sometimes called "large" cap and have "L" pins holding cap on, under rotor weights and screw on rotor. The cap had a window. I said confusing, right?
As far as I can tell the answer to the question is no window 60-62, window 63-65, no window 66-up.

I don't know if there was a clip-on cap for 305 V6 or not. Sometimes the I6 stuff gets confused with V6 stuff. BUT: The Chevy I6 in 60-62 had a clip-on cap. No window in I6, window in V8's. Then in 63 went to "L" pin.

Re: GMC V-6 ignition question
 

Thanks for the answers! I’m assuming the points are identical to their v-8 counterparts, although the condenser is likely a different value...I’ll look it up.

Re: GMC V-6 ignition question
 

There was never a small cap clip on distributor used on GMC V6 engine. The big style cap with the window was used from 1960-65 but around 1965 and even possibly 1964 the small cap, same one used on inline sixes was used on light duty engines while bigger trucks still used the larger window style cap, by 1966 all V6 engine came with the small cap distributor. I don't know why they made the change but the larger cap distributor makes better sense to me because you can adjust the points externally.

Re: GMC V-6 ignition question
 

Greetings Bob!

The points are indeed the same as their V-8 counterparts. There is (or was) a unitized point set that included the condenser which made installation much easier, since you didn't have to fiddle around with a separate mounting screw for the condenser, and the wire on the condenser was also eliminated. See if you can still get the unitized point set. It's definitely a time and cuss saver!

Re: GMC V-6 ignition question
 

Just an FYI --

If you're interested in getting rid of your points and condenser, Pertronix makes kits for both types of distributors used on our V6 engines. They're simple to install. I've installed many of them over the years.

Re: GMC V-6 ignition question
 

all GMC V6 engines through 1963 used the window type of distributor. The change was made in 1964, when GMC went to an alunimum distributor housing and in the interest of interchangeability with other 6-cylinder engines in production (230-250-292) the change was made. All replacement distributors are of the 2nd design and were installed in older engines when a distributor was needed.

Re: GMC V-6 ignition question
 

GEORGE - Delco called them Uni-points, points & condensor combined. I used them in my annual tune-ups in my '70 Nova with 307 from about 1974 thru 1977. I had a bad wire on a condensor leave me stranded late one night. Not even having a condensor wire was a good thing in my book.

Re: GMC V-6 ignition question
 

I agree with you on the elimination of the condenser wire. Another side benefit is not having to fiddle around with that dinky little condenser mounting screw, which no matter what you did, was so doggone easy to drop, leading to a fishing expedition to find the darn thing, right along with a generous helping of expletives!!

Re: GMC V-6 ignition question
 

I'm enjoying all the replies to my question. The responses about the uni-set points/condenser brought back memories of installing them when I was a tech at Kirk Chevrolet - Oldsmobile in Roscommon Michigan. Back then we used to be pretty good at sliding the condenser in without removing the screw completely, but the uniset made things easier. Then GM decided they needed a rf shield covering the points/condenser... now that was a pain! We all had an ignition screwdriver that would hold the screws with a little spring loaded twist blade.

Re: GMC V-6 ignition question
 

Here's a couple of photos... The ignition Shields & screwdriver.

Re: GMC V-6 ignition question
 

Greetings, Bob!

Yeah, it definitely looks like that RF shield could be a royal pain in the behind! I've still got my ignition screwdriver, as well as a good set of ignition wrenches for working on agricultural and industrial applications. As far as staying with point and condenser for your engine goes, I highly recommend the Pertronix Solid State pointless conversion for your engine. Easy to install, and you'll never have to worry about points and condenser again!

Re: GMC V-6 ignition question
 

George,
I'm planning on going the road less traveled with electronic ignition conversion. Pick an existing module (ford tfi remote mount looks like a plan) and use the points to trigger it. The current across the points will be so small they should last indefinitely. One plus of this plan is simple conversion back to points as the primary switch if the electronics fail. I used to use a bench setup of this kind to demonstrate electronic ignition to students. I won't take credit for actually applying to old cars though, got the info from the H. A. M. B. Forum. I'll post a build report when I get around to building it. I also have a couple of tractors that I want to convert.
Bob

Re: GMC V-6 ignition question
 

GEORGE - A word of warning on using the Ford thick film ignition as a base for your system. It wasn't one of Ford's better ideas. I had an '87 300-6 F-150 with it and an '88 302-HO Mustang GT with it that both gave up around 50,000-60,000 miles. Seems the heating & cooling cycles delaminated something inside the distributor. Had to pull the distributor to replace. Lucky Me! Had a '78 300-6 F-150 with Ford DURASPARK, little diecast box on the firewall gets tired after 50,000 and the Standard brand automotive replacement outlasts the rest of the truck.
I finally got smart. Traded for a '96 F250 with the IH built 7.3L diesel. And carried a glow plug relay and cam position sensor with me plus the tools to change them. Of the over half a million miles I put on FORD pickups the diesel got the vast majority put on it, and 25 years old I'd still take it for a long road trip.

Re: GMC V-6 ignition question
 

The remote mounted tfi module took it off the distributor for just that reason. The heat sink should work when mounted in a cooler spot. (and give the option to bypass it in case of failure, reverting to the stock set up). At any rate it promises to be an interesting project.

Re: GMC V-6 ignition question
 

BOB - Good, you've thought that problem out. Neither that F-150 or Mustang was one of FORD'S better ideas, makes me wonder why I've bought several more since.

On your old ag tractors, PERTRONIC's is the brand of solid state replacement system used. They get about 50-50 approval on antique tractor forums. I think the ability of the installer enters into some of the unsatisfactory installations.

Re: GMC V-6 ignition question
 

Greetings, POWERSTROKE!

Regarding the Pertronix Solid State Ignition conversions, the instructions include with them are easy to follow, and the only reason that there should be any complaints with these conversions is that the installation instructions were not followed. Personally, I installed a Pertronix conversion on an IHC Super H Farmall for a friend of mine, and he is extremely pleased with the outcome of that installation. I would have no problem installing a Pertronix conversion on any of the older GM applications. Pertronix is far superior to the old point and condenser set ups of years gone by!

Re: GMC V-6 ignition question
 

This was on a 62 I saw and my first time seeing one. It has a button for conventional or CDI. I remember Heath Kits but I thought they just did radios.

https://i.postimg.cc/sgNmw7V3/IMG-2228.jpg

https://i.postimg.cc/28X4nWFm/IMG-2227.jpg

Re: GMC V-6 ignition question
 

Greetings Funky!

I have to admit, this is the first time I've seen a Heath Kit. From what I'm seeing, it looks to be a bit more complicated to install as opposed to the simplicity of a Pertronix conversion.

Re: GMC V-6 ignition question
 

The Heathkit Capacitive Discharge appears to be the same unit sold as the Delta Mark 10. We put one in the 68 GMC back in 1974, it basically piggy backs on the the ignition coil as I do recall and it doesn't do away with the points. Basically its the predecessor to the MSD6AL. Ran the Delta box for 11 years, about 5 years after installing it my father was driving the truck and it went dead on him, the ignition coil had be replaced. After the truck was handed down to me, some 3 years later I noticed the tach needle bouncing around and not reading accurately, I went so far as to buy a new Factory Tach and still no difference until I disconnected the Delta box to reveal another dead coil. I can assume this Capacitive Discharge box was blowing coils but Ironically after it blew the coil it just did the job as a coil and kept the engine running just fine but was throwing off my Tach, I removed it for good and put in a new coil with the intentions of switching to a true Breakerless electronic ignition so then came the Buick HEI conversion and that was the best thing next to the Holley 500 upgrade.

Re: GMC V-6 ignition question
 

I put one of those Heathkit CDI units together back in the '70s and installed it on one of my trucks. The big advantage as far as I was concerned was that it reduced the current across the ignition points to a small fraction of normal, so that points would theoretically last "forever".

Re: GMC V-6 ignition question
 

Here's the history of Heathkit, from Wikipedia. I had a friend who built their color TV, back in the day...
Heathkit manufactured electronic kits from 1947 until 1992. After closing that business, the Heath Company continued with its products for education, and motion-sensor lighting controls. The lighting control business was sold around 2000. The company announced in 2011 that they were reentering the kit business after a 20-year hiatus but then filed for bankruptcy in 2012,[1] and under new ownership began restructuring in 2013. As of 2019, the company has a live website with newly-designed products, services, vintage kits, and replacement parts for sale.[2]