? Does this problem with Vortec L30 & L31 V8 distributor caps, Also include 4.3L V6 Vortec caps ??
It seems most references here about failed cap epidemic are speaking of Vortec V8.
It seems the Vortec V6 & V8 distributors with "crab caps" are virtually same, but having either 6 or 8 hi-tension cap terminals.
Regardless of any differences between the two; Are 4.3L Vortec V6 owners experiencing same type cap failures and at similar frequency?
Hello rebelyell,
I'm trying to come up to speed on the whole 'shorter than average lifespan' of the V8 Vortec crab cap,
and as an old school distributor guy I realized that I was bringing some of my old assumptions
to a differently stressed high voltage playground.
In short, the pre-Vortec dizzy caps provided a simple, unique path straight up and out from where the
rotor is spinning to where the 8 spark plug wires are connected. (Aka: terminals) All 8 cylinders had a
separate yet
identical path. Old school tune ups mandated performing a good distributor cap inspection,
included taking a good look inside and ensuring that there wasn't carbon tracks between these terminals,
and if there was any doubt at all, replace it.
Enter the Vortec crab cap. Obviously cross-fire creates misfire = increased emissions & lower customer satisfaction,
so when it came time to meet the new, tighter '96 emissions + OBDII reporting requirements, the engineers wanted
to ensure that the factory wiring routing would remain the same for the entire life of the engine. And if you go to a car
show, if you look at 10 SBCs you will see at least 9 different methods for spark plug routing. (One guy brought 2 cars. :0)
Guess what? In order to sort out the spark plug wires according to Left and Right banks, the crab cap was
created. And the failure trend that I'm starting to look for is where the #3 spark plug path crosses the entire cap
and is routed right next to the center terminal. (where all 8 sparks enter and are coupled to the spinning rotor)
This looks to be a highly stressed area from the design. If the manufacturer isn't utilizing the very best high voltage
insulator materials in the cap, it seems to burn through in the area shown in the photo below:
You must be registered for see images attach
(Picture supplied by fellow GMT400 member {I added the arrows} while we were troubleshooting a
sudden no-start on his vehicle. And replacing the cap fixed the no-start.)
****
NOTE: The single biggest thing you can do to take some of the pressure off of your ignition system
is to back off from the original .060" spark plug gap, and run a .045" gap instead. (Per a GM TSB
from back in the day that's floating around.) Note: When I bought my chore truck the first thing
I did was remove the well-worn, rounded .063+" plugs and installed a fresh set of .045" gapped
plugs. 90% improvement in idle & part throttle operation right there.
The second thing to do is find some of
@L31MaxExpress's engine bay photos featuring the attention
to detail when it comes to routing the spark plug wires and mimic that as close as possible.
And the third thing to do would be to make sure the vent is clear and that the ozone being developed
during normal operation is being positively sucked out via his vacuum purge mod. Good stuff.
Last but not least, the things we fix best are those items that we understand most. We all know that
O2 (oxygen) is good for us but corrosive to metals. Well, O3 (ozone) that's generated by high voltage
arcing is even more corrosive than O2, so in a closed distributor we end up with a pretty harsh environment,
complete with a spinning mini-welder forced to work up to ~40 Kilovolts. Check out this short video of a
running engine equipped with a clear plastic HEI dizzy cap:
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NOTE: The old HEI dizzy cap was of large diameter, and with all that real estate underneath the cap it paid respect
with the 'inverse-squared' law that all high voltage circuits follow. So when the design engineers not only made
the Vortec dizzy cap smaller, but at the same time complicated the internal routing from rotor/terminal to
actual spark plug wire, they put a lot more pressure on the insulator material that the cap was made out of.
Final thought:
* '88-'95 TBI V8s ran a .035" spark plug gap per the factory sticker. Nice and quiet over there.
* '96+ Vortec V8s were originally spec'd a .060" spark plug gap. And made more horsepower with better
cylinder filling from the same CID, which again pushes up the KV needed to jump the bigger gaps in the
combustion chamber.
Mil-Spec solution:
Best cap you can buy, .045" gaps on your plugs, and suck out the ozone per L31MaxExpress's recommendation.
Do this, and your dizzy cap will no longer be the LIMFAC (LIMiting FACtor) in your engine bay's reliability.
The next best solution for normal owners who aren't pushing their GMT400 V8s like L31MaxExpress is doing? It would
be to use the best vented cap & the .045" spark plug gaps. And give your dizzy cap a good visual inspection on a
regular basis.
How about this? If your engine is running well now, then treat it to a fresh cap and take the 'known good' spare, put it in
a quart freezer bag, and put in the glove box. Or maybe the bagged dizzy cap in a small cardboard box under the seat. Just
remember where you stashed it. For you might end up helping a fellow GMT400 owner stuck on the side of the road/at the
gas station with a sudden dizzy cap failure. You know, the Boy Scout credo. :0)
Hope this is helpful. Heck, I hope that it's readable.
Cheers --
