Wonky Ignition Firing Behavior on 77 Scout 345

B&GScout

B&GScout

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77 SSii, 345, 4x4, 3 spd, Edelbrock 1406 with 5.5 psi regulated fuel pressure supply. Carb has stock rods and jets. Note until recently engine ran fine with this carb set.
Gold Box with Holley electronic 3* curved point Dist plumbed to ported vac on carb (passenger side).
Carb is tuned, 20“ manifold vacuum, A/F mix happiest at 2 turns each based on vacuum and rpm readings, hot curb idle sitting at 675 RPM. Choke fine.
Plugs all clean. *Wires all well seated on both ends*
Base timing 8* (tried 10-12* and in doing so noticed the below timing light behavior. Read on).
Distributor cap looks healthy, clean, seats well. Rotor same. No noticeable wear on either. Bushing seems fine, no wiggle.
Just replaced bad vac advance and new one from IH Parts is working fine. Mech timing seems to be fine and fully functional. Total timing is >25* scale.
New and correct PVC Valve.
No detectable vac leaks.
Fuel filter is good.
Just filled gas tank with fresh non-ethanol. Didn’t just top-off the tank, it was low. And that existing, remaining gas was only bout a month old.

Engine starts fine, does not struggle. Easily starts when cold and hot, rain or shine. Rock solid engine temp while operating.

In earlier thread I inquired about use of Flamethrower coil, but I am still using existing coil which Ohms at 1.5, doesn’t get hot. There are a number of photos of my dist there in that thread. (See “77 Scout 345 Coil Upgrade to Pertronix“ (started thread on Feb 13, 2021).
Am sitting tight on coil change so as to limit introduction of too many variables. So the only changes made as of late are new the PVC, plug wires, and the faulty vac advance canister replaced.

OK, so all above is background info.

My Situation Now
Been chasing small miss, I’ll call them bobbles. Detectable at idle, a bit more pronounced when slightly accelerating in 2nd and 3rd gears. No backfiring, pinging or anything like that. Ditto on hard acceleration once at highway speeds 55 MPH+ no pinging, no bogging.
Not smelling any excess exhaust or rich fumes at any time. It’s just those darn bobbles.

Here’s what I am homed-in on at the moment: I noticed when checking timing (#8 cyl) my standard timing light was in sync with the bobbles — engine would barely stumble and light would as well. Hummm...At first thought maybe timing light not picking-up well around plug wire, light was fine. Now I am thinking.... And since I can hear bobbles on both sides of engine via dual exhaust sounds I checked all other cylinders. I see same bobble result on cylinders 1, 5, 4, 8. Other 4 cylinders don’t miss a beat. This is very consistent, not random. Its actually very rhythmic.
Behavior of timing light aligns with bobbles and indicates some sort of ignition miss.

Scratching head. Is it time to pull gold box along with the dist electronics and install Pertronix? Many wise warhorses haunting these forums report the gold box is either off or on, no in-between and doesn’t exhibit these sorts of bobbles. I do wonder about the electronic module inside the dist??
*Also need to advise I just replaced plug wires with 8mm set.* Verified proper wire location/firing order — I don’t have any wires mis-seated.
These are quality wires but are a universal set I had to terminate myself (dist end) using good crimping tool. Like to think I did good job there. But did I?
Note I was very thorough with terminations and I DID ohm all wires after I built them. All ohm’ed fine, very low. (Am gonna take another close look at wires, will swap a “good” one with a bobble one to see what happens via timing light behavior.)

Anyone ever run across these ignition/firing bobble symptoms? What is that timing light telling me?

Paul
 
Check the voltage at the positive coil terminal while running and let us know what you find.
 
Chappie, I see 3.6 volts — measured from positive to negative across coil. When engine is running.

I have 10.6 volts when engine off, key ON (briefly for test), neg coil term grounded via jumper, meter pos lead on coil pos term, meter neg lead on ground.
I have 12.8 volts with same above config EXCEPT pos wires removed from coil and meter is on the pos wires (not coil).
Battery is 13.2.

As another check I connected a jumper, with engine running, direct from pos battery to pos coil term. Still 3.6 volts across coil. Looking for voltage loss now, where's it going?
At risk of TMI, during this round of work I encountered a rogue hot wire once buried in wire bundle. I surely must have disturbed it and it made its presence known. o_O The plastic connector covering the spade connector of that rogue was disintegrated. That bare spade contacted the heater control cable near bulkhead. Htr cable got really hot (welded inner/outer cable together). Wires running from Gold Box were laying against that htr cable. There is some heat damage to the insulation on wire going to dist that mates to the Blue wire on GB pigtail. Yellow side looks unscathed. Can’t be a coincidence.
 
Your distributor is not a Holley curved (or any other type of) breaker points. It's a Holley electronic with a reluctor wheel (mini throwing star) and internal pickup module (tiny black device with wires attached) that work in unison with the remote amplifier module on your firewall that is gold in appearance...collectively these components are often referred to as a Holley Gold Box system. Remote amplifier failure, from what I understand anecdotally, tends to be an all or nothing deal, with one or more temporary failures to start and or run, followed by intervals of apparently normal operation, which is then followed by permanent component failure. I'm not familiar with failure modes or behaviors that could be or are exhibited by the internal pickup device, but being that it is electronic, it like any similar device must have an expiration point. Please understand, I'm not in any position to suggest that your internal module is causing your reported symptoms. I'm merely speculating on it being a possibility to consider.
 
Oops, here is photo of damaged wire. The light blue connector to nowhere is the rogue. I capped it with the blank connector. Appears that rogue runs back towards bulkhead. Old elect choke wire? Dunno.
In my fingers is the lead from the distributor that mates with Blue & Yellow pigtail at Gold Box. You can see the U-shaped heat damage. It’s not bare wire anymore but may have been for a bit when the heat was on. Insulation must have slightly healed but damage was surely done. In effect it’s now a likely resistor.
Sorry photo flipped 90*.
so
7ABAD00D-4CF0-449A-BAA4-9E4D2E9A6B28.jpeg
 
It's good that you found that when you did. Let's hope that getting all that tomfoolery abated solves your performance issue.
 
If I now abandon GB in its entirety and go with Pertronix Igniter that will allow me to not worry with that wire repair, right? And just pull GB system out.
If so, best option for source to switched 12v for dist? Is there a wire in the harness feeding GB I can use?
 
The answer to both questions is Yes. Is there not enough excess in the damaged wire to snip out the bad and reconnect? I'm not a fan of splices in wire runs, but as an intermediate step and just to see if it makes your bumble bees go on hiatus or not. Just typing out loud.
 
Hopefully this fix solves the bobble you describe. Its possible the bare wire was grounding sporadically and shunting the signal causing the miss.
I am not a fan of the GoldBox. I have a truck that has been in the family since 1975. Between my dad and me, its seen well over 5 replacements. I would always grab them at the junkyard even when I wasn't looking for Scout parts. Many of the failed units died slowly over the course of a week or so. Not unlike the situation you describe. Until the point where it goes paws up.
Despite others chiming in about Pertronix longevity and performance, I can say I have had the same Ignitor 1 in this truck for nearly 30 years. I had to modify the reluctor to fit the distributor because it was made for a points set up before Pertronix made a kit to replace the Gold Box pickup. So longevity....? Pretty good I'd say. I have installed 6-7 in various other vehicles including other IHs, never had a problem. So if you get tired of chasing Gold Box problems, this is one option.
 
Thanks both. I’ll get a Pertronix coming. And in meantime I’ll splice the bad wire section on dist wire to see if in fact that solves the problem. Either way the Ptron is going in.
Am curious, what voltage should I normally see across the coil? Chappie, you still got your ears on?
 
You won't see any voltage "across" the coil. Just because there is a + and - the reality is they are both positive voltage. The + gets voltage from the ignition switch and then also powers the Pertronix. The negative post goes to the other wire of the Pertronix to trigger the coil for each firing event. This is the same for the Gold box or points.
If you do the Pertronix, you'll want to make sure there is no resistance wire or porcelain resistor. If it was an original Gold Box truck, there shouldn't be. The Pertronix will want full 12v. Buy the recommended Pertronix coil too.
Incidentally, if you were to ever think about fuel injection, you could also modify your distributor to accept a GM HEI pickup and amplifier. Look for Bill Hamilton's write ups. He sells Hamilton EFI kits here and his timing mods are what's needed. But its also a stand-alone alternative to Pertronix or any other electronic conversion. At a fraction of the cost. You just need to be handy with some of the fabrication.
Let us know how it goes!
 
Lots of water under the bridge since I asked the question. Unfortunately I was not specific enough in my question. I wanted to know voltage to ground while running. Was looking for low voltage. Petronics is a great way to go, the one in my Scout is about 30 years old and never missed a beat.
 
This is good stuff, great community. Thanks again.
I spliced the bad section on dist wire. It didn’t help. Dang It!
Closely examined the damaged wire section. The insulation was definitely damaged but wire strands all visually look fine in the damage section I removed and likely it was doing its job. Oh well. Still have the bobbles. Nothing is easy!
Have Pertronix Igniter on way. Should be here mon or tues.

Chappie, voltage you had me check is 11.8 with engine running, meter on pos coil term, meter neg lead on engine ground. Battery at that moment was 12.2. All seems fine there.
Dealbreaker, you are correct in that there is no porcelain resistor in my GB config. Nor is there the old 72” resistor wire. Looks to be a clean GB config.

Will let yall know how the Igniter works out.
 
12.2 volts at battery with engine running or stopped? You should be seeing in the range of 13.5 to 14.5 volts across the battery terminals while the engine is running. Might need to blip the throttle to make sure the alternator has been excited to begin charging. If you don't see those higher numbers especially with increased revs, then you have a charging issue...which would absolutely have a detrimental affect on the lightening make it happener system.
 
Scoutboy, Alt is ok. 14.6V at battery and 14V at coil. Thanks for spotting that. So appreciate you guys wracking your brains and turning every stone. Engine was loping when I did earlier/above volt checks. When rpm at 700 or so, all’s well.
 
Update. Ignition bobble/missing problem solved. It was loose plug wires on distributor cap. Yep, it was.
Recall those new 8mm plug wires with 90* boots on distributor that were tricky to fit/seat well in cap? Boots were crowding each other. When engine warms, the boots are more pliable and some would creep up the tower. The boots were just too thick and would push/shove on each other and could unseat clip ends and actually loosen the wire.
Explains why I could get engine ok only to have it go wonky again later. At first it was consistent with certain cylinders then became more random days later as I probed around, resetting boots, checking wires, gold box, reluctor, etc looking for cause.

Very ok for yall to smile. I did. Bonehead on my part. I knew boots were cramped. Just didn’t think they could actually loosen a clipped-in plug wire. Live & Learn. Its usually something simple.
Will still convert to Pertronix Igniter once it arrives in next day or 2.

Thanks again and warm regards gents,
 
No one is entirely immune from the self-inflicted wounds when working on these rust piles. Glad you figured it out and that it was something so easy to remedy. Thanks for updating us.
 
Oooh good...an easy one! Many of us have gone all hot-rod on the Scout motor with the 8mm wires. For your next set, save the hassle and get the Packard or Standard 7mm set from RockAuto with the straight boots. Looks clean, no fuss with connections. And like Scoutboy says, go NGK 3332s the next time you do plugs. That's a change you'll actually measure on the Butt Dyno.
As for the Gold Box, it'll break your heart sooner than later. They always do. Good you have a plan in place.
 
Yeah, I put a set of 8mm...I forget which brand on my Scout engine years back. They were meant for a BB Chev, but they worked well for my app...but I have a Delco dizz so I think the tower spacing on that cap is a bit less crowded than on a Holley cap.
 
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