Re: Need ignition upgrade help/advice.
 

Right you are... part of the reason I try to stay off forums sometimes unless necessary.

You guys mind as well just have at it and keep rolling, as I said before I'll update as I go.

I have to get a sticker this month and drive it in the Memorial Day parade. So by next week I'll have a chance to play with the engine for a bit. I'm going to check the vales again too. I did them once but the engine wasn't hot enough so I'm sure the clearances are off.

Re: Need ignition upgrade help/advice.
 

Checking in for an update...

Over the past month I reset the valves while hot (some were pretty tight). That made a bit of a difference now that they are opening and closing properly.

I also ordered a set of .059 jets, two sizes up from the recommended. Just got through installing them and going for a test drive. Definitely a bit more responsive when shifting up. Top speed pulling a hill at 45, seems better.

I may take it to a cruse night tomorrow and see how it does on a short trip power wise. I should really throw a 2000lbs tractor on the back and see what happens...

The initial goal is to do a 85 mile round trip to a tractor show weekend of the 22nd and 23rd. Lots of hill climbs on that trip, could have a nice parade behind me!

Re: Need ignition upgrade help/advice.
 

Get rid of the points ignition and go with electronic ignition. My choice is the GM HEI and there is the Pertronix which is an easy retrofit because it fits into your stock distributor.:thumbsup:

Re: Need ignition upgrade help/advice.
 

For the HEI upgrade check out jolly's www.6066gmcguy.com site under V6 performance upgrades. For the Pertronix conversion go to www.vintageperformance.com/retrorockets.:upyes:

Re: Need ignition upgrade help/advice.
 

Thanks Bigblock. That looks like the next upgrade I'll be doing. May lean towards building the HEI distributor if time allows. A couple owners before me converted the 350 on my '77 GMC pickup to HEI. For an older carbureted engine, it starts fast and runs great.

Re: Need ignition upgrade help/advice.
 

That's odd because a 77 GMC would have come with an HEI as standard equipment:whattha:

Re: Need ignition upgrade help/advice.
 

Maybe it was. I don't know much about the 70's years... The guy put a mild cam in it along with a Edelbrock 500cfm 4 barrel. Distributor was replaced too with one of those fancy aluminum looking ones... blue distributor HEI cap... so I just figured it was converted.

He used to pull a trailer with it from Colorado to New Hampshire so it was built up some.

Re: Need ignition upgrade help/advice.
 

5tractorguy, I put on an MSD6 and MSD coil on my 478 in the Massey tractor. The points in the distributor only act as a trigger so they do not wear like they do when running normally. It made a great difference, starts better, runs better, plugs stay cleaner with my larger jets. An MSD6al has rev limiter chip capability if you want that. There are many MSD units for sale on Ebay. I have bought five of them there to put on various pieces of equipment, cars and trucks I have. I have never run a Pertronix so I cannot offer a first hand experience to compare them to MSD. I just know we are very happy with the MSD system.

Re: Need ignition upgrade help/advice.
 

+1 Dave. I would add to use premium wires.

Re: Need ignition upgrade help/advice.
 

Yes, HEI was used as early as '72/'73 model year on some engines, Chevy used it a lot in '74, and on everything in '75.

I had a '70 Nova with 307 V-8, and a '77 Firebird with 301 V-8, HEI was a much better system.

Installing an MSD 6AL sounds like a great idea. They make speed limiter chips low enough to match the Big V-6's operating range, 3000-3800, and 4000-4800. Take your pick.

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:

Re: Need ignition upgrade help/advice.
 

Back in the early 70 I had a jeep with a Buick 225 V6, odd fire. It had a symmetrical distributor cap (just like the inline 6 engine) but the rotor and the point cam was different. I had to be sure when I had to pull the distributor that I get the number one distributor tower aligned up with the rotor when I reinstalled it. Having it off one position and moving the plug wires to compensate would make the engine run rough.:banghead: