Re: Need ignition upgrade help/advice.
 

Yes, Pontiac introduced the first version in 1972 for their 455 HO that appeared to look like the HEI. It was called a unitized Ignition, the unit wasn't quite as big as the later HEI distributors but somewhat similar in appearance.

Re: Need ignition upgrade help/advice.
 

Peter, Pontiac, had "unitized ignition" as an option even as far back as 1963. However, it used the standard window cap and a divorced module that looked like a 9000490 transitorised voltage regulator. I know most people like the freedom of HEI, but I have not had good experiences with it in it's early years. That is why I still like points/condenser set up.

Re: Need ignition upgrade help/advice.
 

I had a look through ebay. Seems to be plenty of units to choose from out there. Looks to be another route I can take instead of building an HEI unit. Will probably be an easier conversion in the long run too... and I've heard plenty of good things about the MSD's.


Good info Powerstroke!


Prepping the truck today for the trip Friday. Grease, oil, fluids etc... I pulled the distributor cap and checked everything last night and cleaned the brass contacts on the inside of cap. That's about as good of an "upgrade" as it'll get before this trip.

May check the timing again too. I played with that a bunch within the first year of getting the truck. I ended up leaving it at the stock 5deg before and running it.

Re: Need ignition upgrade help/advice.
 

Made the 90 mile round trip this weekend. Truck did a bit better than I figured. Most of the big hills I pulled at 15-20, moderate ones at 30+/-. Aside from that, I kept it pinned at 45 and it sailed right along. Seems like those .059 jets helped out.

Estimated MPG was 7-8, which was dang good especially with a loaded truck and a 351.

Ignition upgrade will come down the road sometime. As for now, I'm glad I was finally able to road trip it farther that just 10-20 miles around town.

Thanks for all the help so far.

Re: Need ignition upgrade help/advice.
 

Looking at getting a used/rebuild MSD 6a for my 351 V6 - there are 3 different models of 6a which of 2 are for street/strip. The model 6200 is for 4-6-8 Even Fire motors and the Model 6246 is for Odd-Fire V6 - I know of Buick odd-fires that was used in the older Jeeps - would the GMC V6 be Odd-fire since there are people who rebuilt the Buick disturbtors for there GMC V6's to get HEI - only question I really need to know is the GMC V6 odd or even fire. :signthankspin: - Cliff

Re: Need ignition upgrade help/advice.
 

The GMC V6 is an even fire engine. This is due to the 60° angle of the block. The Buick V6 has a 90° angle on the block which is why it is an odd fire engine. Some of the later Chevy V6 even fire is a 90° angle block but the crank rod journal (where the two rod come together on a common journal) is shifted 15° to make it an even fire engine. The early Chevy V6 is an odd fire because the crank was not shifted 15°.

Re: Need ignition upgrade help/advice.
 

Not quite accurate:pullinghairout: 1978 on up Buick V6 engines are even fire!! What Buick did is offset the crank journals to make the engine fire like a V6 at a 120 degree angle. All f us that use a Buick HEI on our GMC V6 engines are from 78 and later even fire engines. Chevrolet really never built a fully even fire V6 out of their 90 degree block, it was a compromise, they didn't offset the rod journal on the crank as much as Buick did figuring it wouldn't weaken the crank as much but even the 4.3 Vortec still had some shake to it in the lower rpm range while the Buicks were as smooth as silk!!:upyes:

Re: Need ignition upgrade help/advice.
 

Dad had a '66 Buick Skylark, fancy Buick Special, 4 door coupe, with the 198 V-6, had the odd fire crankshaft, really sounded busy with a little RPM. Hooking that little V-6 to a Powerglide trans was a mistake, but with H78x14 snow tires it would run 70 easy in low. One often ignored problem with the odd fire engines was they were hard on timing chains & gears/sprockets. Bad harmonics from the irregular loads on the timing gears. Dad drove to/from work at odd hours of the night and day and the timing gear decided to pitch the nylon molded onto the cam sprocket about half way home one morning about 2:30. Was an ALL DAY event getting the car repaired, just made it back to work about 3-3:30 PM.
The Big Block V-6 engines being truck engines used more reliable gear driven camshafts. Can't say I've ever heard of a gear drive failing. Another unique feature was GMC putting the spark plugs inside the V of the engine, keeping the plugs away from the heat of the exhaust manifolds that typically glow orange hot while the engines are running hard. Heat doesn't effect the spark plugs but plug wires last many times longer.

Re: Need ignition upgrade help/advice.
 

Thanks for the reply:goodjob: - this should be helpful for others as well when doing ignition upgrades by either going with a MDS box or different disturbator. Didn't know that a MDS box would know the difference between odd and even since it's triggered by the points. :signthankspin:

Re: Need ignition upgrade help/advice.
 

Thanks for correcting my info. The info I had was base on what I remember from reading one of those car magazine back in the 80-90, maybe my memory cell lost some of the info. :ahhhh: