Howdy, had something happen today that I've never seen before, curious if anyone else has had a similar experience. Short version: I had 6 new AC Delco plugs fail with less than an hour of run time. Longer version: I was working on my wife's '48 Chevy sedan delivery with a '76 Chevy 350, it's a stock engine, no crazy mods. A couple months ago I had changed the plugs and wires and there was about 30 minutes of run-time on both, but it wasn't running well. I had time today so I was checking the timing and the engine started missing, I shut it down, made some adjustments and checked connections then fired it back up and it was worse. I shut it down and checked everything again to make sure all my wires were connected correctly, right firing order, etc. and when I restarted it, I could barely keep it running. I felt the p***enger exhaust manifold and it was only warm to the touch, driver's side was hot. Messed around with it some more and I couldn't get it to run at all. I pulled all the plugs, put them back into the wires and laid them across the manifold and cranked it over, and I only got spark off a couple. I went through and checked all the plugs and only two were firing, I checked those 2 plugs on all the wires and they were good. The other 6 wouldn'd fire on any of the wires. Basically, over a period of about 30 minutes today I had 6 of my 8 plugs fail, they were AC Delco R44T Copper core, purchased new and they had less than an hour total run time. I changed them out for a set of new NGK plugs and the engine fired off and ran smooth, no issues. Bad batch? Has anyone seen this before?
@Ryan Skiles By chance did you look in cap & rotor . Also did you move the non firing plugs to the known leads ( spark plug wire) that where firing just to verify each non firing / bag plug? Or ignition firing tester between plug wire & sparkplug .. If you still have the plugs , go to another Vehicle & just hook up one plug @ time to see if fires , make sure you ground plug . I had a issue like 40 years ago 44T where bad around 3,500 rpms like a rev limiter good before & after , took me a while to figure out change plugs no issues after.
Two obvious possibilities, bad plugs or something not often thought of, damage during shipment. It's pretty rare in either case. You might want to contact the maker and see if they want to do a QC on them and have you ship them back (on their dime). Tuneup masters tried to use some eastern Europe sourced TM branded plugs. They didn't last long on the shelf or in cars. I've seen Champions with the porcelain that broke around the center electrode. Tip pointed up, it looked fine. Tip pointed down, the gap was shrouded by the insulator. Both of these were in the 80s, but they stuck with me. AC was usually fine, but I did prefer NGK. Again, this was last century, so changes have almost certainly been made since. Haven't changed many plugs recently.
@Ryan Skiles AC Delco RT44T's are now made in China [so it is a lucky dip] Check the resistance of the plug core, and also check for continuity of the tip to the threaded body [I've heard of plugs with hidden cracks in the porcelain causing shorts. NGK aren't immune t these problems [just less likely] I have an O/T Aussie Falcon SW Barra that runs NGK iridium plugs [which are expensive] I've been chasing my tail on an under load misfire, so I replaced the NGK's for another set and the problem went away. 3000 kms [2000miles] later the misfire was back haunting me. Now "I knew" it wasn't the plugs because they are good for 60000 miles, So I purchased a new set of OEM coil packs. But the misfire still persisted under load. Now me being the "king of cheap" had another Falcon, so I swapped plugs from vehicle to vehicle. The misfire followed the plugs to the other vehicle [I should've done this before buying the coil packs] Anyway I purchase another set of iridium plugs and the problem was solved ............ Or so I thought. Approx 3000 kms later and the misfire was back. Now I was getting pissed off replacing spark plugs at $25.00 each ,so I cheaped out and purchased a set of cheap NGK BKR6e's [$4.50ea] It turns out than Ford used this plug in their turbo Barra engines [so all the voodoo "bone pointing" about burning out the coil packs etc is pure ********] It's been running fine ever since [$27 vs 2 lots of $150]
The two things I have found to be good at killing plugs quickly is too much fuel or too cold plugs. Both scenarios prevents the plugs from getting hot enough to burn off deposits during low power usage (idle/cruising) and eventually the buildup prevents them from making good spark, either by insulating or short circuiting them. In this day and age we also have to consider the possibility of fake parts, the chinese have a habit of putting brand names on their own (usually inferior) copies, so unless you can be sure they were actual AC Delco from some large chain selling that brand you never know. That cheap ebay purchase from some noname seller could be cheap because it's fake parts.
I have never got a bad NGK plug , been running their racing plugs in the coupe for 25 years in various SBC engines. I usually buy multiple sets right before the season starts from Summit.
Go to "Rock Auto", type in the NGK part number (the 4 diget #) and check the price. You'll be floored.
I went through the exact same thing a few years ago with some AC Delco plugs. Except mine ran good for about the first 500 miles. Two different sets of them. I switched to a set of NGKs and have been good ever since.
I've gotten new plugs with gaps way off. I always check them before use. If the gaps are wonky the plugs can foul quickly and quit firing.
That's really strange. For like the last 20 years I can only think of a single one that didn't work at all.
Plugs never come pre gapped, you always have to gap them to your application. The same plug used in different engines can have different gaps depending on the engine.
I had a bad one a couple years ago in my little yard tractor. Intermittent miss on a 3 cylinder engine. Brand new NGK plugs, one would randomly ground into the threads. Replaced the one plug and it's been fine ever since. NGK is not immune to defects.
I buy all my spark plugs thru sparkplugs.com (big brown truck) even tho I live where there a hundreds of outlets for them. NGK is choice for racing and if they are stock for the vehicle. Fords only get Autolites.
Spark plugs...I recently took a set out and put them back in. Not that it matters, but that many not p***ing a current, you have to wonder? A picture is worth a lot of questions getting unanswered. Ok...maybe it's me, but someone has to ask, was this an example of FAFO? Because it sure sounds like it. I say that because many a times, I did. Not saying it is, just if it sounds to good to be true, what do you think? My question is did you repackage them and return em or just **** it up and get the NKG's that seemingly fix things?
Not a FAFO situation but I appreciate the question, I went through the plugs systematically trying them on all leads: the good ones were good in all locations, the bad ones were bad. The bad ones had previously been good until they suddenly weren't. All 8 were purchased at the same time. No, I didn't repackage and return them, they're sitting on my bench. When I replaced them with the NKGs it fired right off without missing a beat. Here's the plugs. Here's the plugs
What’s the recommended gap? Those plugs have large gaps? Also seems from the pics, that the ground electrode is past the centre ekectrode.
45 for HEI (75-up) also ranged up to 60. 35 was common for points. So long as they aren't very tight or very large, that shouldn't be the spark/no spark he's experiencing. The ground strap 'shrouding' or completely covering the center electrode is common. Racers may cut this back at the cost of plug life and might get a bit more HP. See pics here. http://www.wallaceracing.com/plug-reading-lm.html
I've never had luck with AC plugs. NGK for me was hit n miss (no pun intended) as they were great in my sleds and Harleys, junk in less than 10 rounds and the drag strip. I see a lot of love/hate for Autolite around here, but those have yet to fail me. I ran the same Autolites in my racer for a full season. Cleaned and gapped just once. Champions used to be the end-all do-all for me, some time in the 90s I couldn't trust em any more. Today's "imported" parts are rolling the dice. I have **** load of new plugs in their OG boxes from the 70s and 80s. I don't have them all cataloged but perhaps I should. I think I have like 2-300
Cool, As an excuse to discover something new, how about taking a meter to them and checking resistance? You have 8 so a pattern may appear? And they should have a value to compare to listed somewhere? I ***ume you identified the failed plugs from the ones that still sparked? Someone mentioned the coil, I'll ask specifically about the distributer, have you looked at the cap and rotor? Admittedly, I looked at it and thought, that's weird, when did they redesign that? I don't doubt a problem exists, but has a plug change cured it, I'm not so sure. In this instance it was the distributor as the cause. But who knows, maybe you did just get a bad batch of plugs? As far as testing the plugs past a resistance check, I'm also going to ask if you have a HF GTAW at home? I'd be curious if they'd p*** a HF current through them?
I think the vast majority of us here have had a brand that was once trusted burn them. What they sold back then isn't what's coming across the counter now in a vast majority of cases. Even if it's the same plant and the ins***utional knowledge did get p***ed on, production output and profit margins are even tighter. The only constant is change. That doesn't always mean better.
Ebay is loaded with metric **** tons of old US made spark plugs. I also buy old nos US made tune up stuff at swap meets when I see it. It started a few years ago when I went to my local auto parts to buy some points...the guy looked at me like I was nuts. It was then I realized that no GM car had had points for 40 years at that point. I felt old. I also laughed when he said tbe offshore **** points they now sell were $18. It takes longer to get the parts you need..but you won't have the problem the op did. The old nos stuff can often be had for a song to boot.
The spark will find the path of least resistance I wonder if the plug gap was large enough on those 6 plugs that the spark then found another way to ground. Cap/plug leads/coil lead/rotor arm….
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