Distributor Upgrade: HEI, odd fire vs even

[OldRed]

Hello folks,

I purchased a 1961 GMC 1000 series with the big block V6 this past fall. With the warmer weather here in Maryland I finally got around to spending some more time working on it. When I bought the truck it had been sitting for about 2 years, the previous owner purchased it from someone who must've made some cheap body repair (which has led to a good amount of rust now) and was basically driving it around town for fun on the weekends. It was going to get a total restore, ended up sitting outside for a while, and I wound up buying it as a non-driving, non-running project.

I wanted to make sure she would run before moving on to fixing the brakes/clutch (it seems there's a leak and therefore I'll have to upgrade to separate hydraulic systems and replace the clutch). I did not have spark, and rather than buy a new ignition coil, I figured I would upgrade the distributor as so many of you mention it makes a huge difference. Unfortunately, in my haste of night shift and excitement, I did not realize that there is an even fire Buick v6 and an odd fire, and purchased an aftermarket odd-fire HEI distributor.

I have already installed the new distributor, with the old gear from the points distributor, I purchased the collar/sleeve for it from a fellow member on here, and I also pulled my mechanical fuel pump (it went bad) and replaced it with an in-line carter electric fuel pump. I have spark at my plugs, and fuel to my carb (it came with a Holley), but the truck just won't run. I am 99.9% it's due to timing, which I can't get right because the odd fire distributors don't match the even fire.

So...in an effort to conserve just a bit of money....am I correct in thinking I can purchase just an even fire cap, and new mechanical weights for inside, and swap those two things? Or is there more to it? Does the internal HEI module need to be swapped? I really want to avoid having to purchase an additional distributor but don't want to continue making my life harder. Any advice is much appreciated, thanks!

[James]

I don't believe buying a cap will fix the problem. The stator that is below the rotor is made for an odd fire engine (the moving targets are not evenly spaced). That's is why when installing an odd fire distributor that the number one on the distributor aligns with cylinder 1 TDC on the compression stroke. Otherwise (getting it off by one post on the distributor by moving the wires trying to make it aligns) the timing will be further off on all cylinders. Odd fire timing intervals is: 90°-150°-90°-150°-90°-150°. Even fire timing intervals is 120° between cylinders.

I hope this help. And yes, you will need to buy an even fire distributor to make it work correctly.

[OldRed]

James,

I appreciate the reply. From what I gathered on the internet, four parts have to be replaced. The cap, rotor, pick-up coil assembly, and the main shaft reluctor (the part you mention). The first three are pretty simple to find online and purchase, however, I don't seem to be able to find a reluctor so far, so it looks like I will be purchasing a new distributor.

[lizziemeister'sV6]

Originally Posted by OldRed

Hello folks,

I purchased a 1961 GMC 1000 series with the big block V6 this past fall. With the warmer weather here in Maryland I finally got around to spending some more time working on it. When I bought the truck it had been sitting for about 2 years, the previous owner purchased it from someone who must've made some cheap body repair (which has led to a good amount of rust now) and was basically driving it around town for fun on the weekends. It was going to get a total restore, ended up sitting outside for a while, and I wound up buying it as a non-driving, non-running project.

I wanted to make sure she would run before moving on to fixing the brakes/clutch (it seems there's a leak and therefore I'll have to upgrade to separate hydraulic systems and replace the clutch). I did not have spark, and rather than buy a new ignition coil, I figured I would upgrade the distributor as so many of you mention it makes a huge difference. Unfortunately, in my haste of night shift and excitement, I did not realize that there is an even fire Buick v6 and an odd fire, and purchased an aftermarket odd-fire HEI distributor.

I have already installed the new distributor, with the old gear from the points distributor, I purchased the collar/sleeve for it from a fellow member on here, and I also pulled my mechanical fuel pump (it went bad) and replaced it with an in-line carter electric fuel pump. I have spark at my plugs, and fuel to my carb (it came with a Holley), but the truck just won't run. I am 99.9% it's due to timing, which I can't get right because the odd fire distributors don't match the even fire.

So...in an effort to conserve just a bit of money....am I correct in thinking I can purchase just an even fire cap, and new mechanical weights for inside, and swap those two things? Or is there more to it? Does the internal HEI module need to be swapped? I really want to avoid having to purchase an additional distributor but don't want to continue making my life harder. Any advice is much appreciated, thanks!

There's a NOS GMC V6 distributor that fits your truck on Ebay at this very moment. To make your life simpler I would purchase that distributor and throw all the mis-matched cobble parts you have in a box and put it on a shelf. With the new distributor your truck will be running and you can enjoy it. Pretty easy (plug and play). I see this happening alot on these old trucks and cars - people buy them and start upgrading them before they even know what they have. Most end up never finished and left in a garage or back yard in a sad state of affair. Sadly they end up scrapped and gone forever. Learn what you have before you start "improving". Work smarter not harder.

[OldRed]

@lizziemeister'sV6 you say it's a NOS distributor, so it's a points distributor? I hopped on ebay and was looking but did not come across anything on my initial search, but I'm also at work where there's restricted internet access so I'll give a second look when I'm home in the morning.

[lizziemeister'sV6]

Item # 276815651795 (GMC V6 distributor) - Yes it has points. Nothing wrong with points - that's what I run.

[Pfroman]

Originally Posted by lizziemeister'sV6

Item # 276815651795 (GMC V6 distributor) - Yes it has points. Nothing wrong with points - that's what I run.

You prolly know but If you go back to points with standard wiring, make sure your ballast resistor and coil are correct and working. I went to a Pertronix conversion and got rid of the resistor (and the crazy fusible links) altogether and swapped the coil. Also went with and AAW classic upgrade wire set.

[James]

Originally Posted by Pfroman

You prolly know but If you go back to points with standard wiring, make sure your ballast resistor and coil are correct and working. I went to a Pertronix conversion and got rid of the resistor (and the crazy fusible links) altogether and swapped the coil. Also went with and AAW classic upgrade wire set.

Ballast resistor? Do you mean resistor wire that run from the firewall to the coil? I'm unaware of a fusible link in the ignition system.

[OldRed]

Thanks for the info, yea I just ran a new wire to power the HEI distributor but did not remove the old wire, in case I ever went back to a points distributor.

I ended up purchasing an even fire HEI distributor off rock-auto for $63 bucks, which will be here Friday afternoon.

[Pfroman]

Originally Posted by James

Ballast resistor? Do you mean resistor wire that run from the firewall to the coil? I'm unaware of a fusible link in the ignition system.

Hi James-

My original wiring on my 64 had fusible links to the starter and a resistor wire from the firewall. Before I put in the pertronix unit I had changed to the AAW wire set and needed the ballast resistor per the instructions for a points set-up. So yes you are correct- originally it was a resistor wire. And there were fusible links going to starter, voltage regulator and some of the relays. The new wire set and fusebox gets rid of all of that thankfully. It was a bit pricey, but worth it I think as the old wiring was basically a huge fire hazard.

On another note- Have you experienced any oiling problems to the valve trains. I'm getting next to nothing up there?