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What Plugs

1685 Views 25 Replies 12 Participants Last post by  USMCMP5811
I need to replace my spark plugs and just wondering what are the best ones to use for the 5.9L engine?
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Autolite 3923 is what you'll want :bigthumb:
i like chapmpion truck plugs. the A3923 is an OK plug, only diff is its one heat range colder than stock. the 4070 champion is also one heat range colder than stock, but is a better made plug. or if you just want normal plugs get a champion 70, which is also one range colder.
(regular heat range for chapions are 4071 and 71 in the same order)
everyone likes their own certain plug, get whatever suits you best.
i just installed the 3923s and they seem to work good. Haven't driven it yet, just fired it up to make sure they were all wired right.
It sounds maybe a smidgen better. The +4s were getting a little gray on the ends.
Autolite 3923's and gap them to 0.035" :bigthumb:
why .35? I did 40 as per the factory requirements.
I may check into the Autolites or get the Champions. I used an Autolite on my dirt bike as I needed a plug and the dealer was closed and when I went to take it out the plug broke in half still in the bike after that I have not used them and not sure if I want to use them again.
I picked up the Autolites they were pretty cheap also. Now I need to find some wires I wanted MSD and last time I called Advance Auto Parts told me they had them turns out they have Mallory's for a similar price which I a$$ume are what they were telling me were MSD's. These are cut to fit which I don't want and he didn't reccomend either.

They had some Autolite Plug wires how are those? Which ones should I Run? I'm going to be using a Napa Dist. cap and rotor. I'd really like them to be red but that doesn't really matter I'm more looking for preformance.
I might just order the MSD's from Summit although they do cost a lot more than the Autolites.

Which degree angle do I need or does it not matter?
I had excellent results with Bosch platinums (just the single tip, not the fancy 2 or 4 tipped ones).

You will get as many opinions on spark plugs as you will with what kind of oil people think you should run!

just an update on the Autolite 3923's I installed a week ago. Truck doesn't run rough at startup anymore, seems to have about the same power, maybe a bit more (could be a plasebo effect).
The +4s were not unserviceable, they were a light gray color, which is good. I have kept them in the event the Autolites foul out or something else unforseen happens.
No pinging either. Fuel mileage is steady at 12-13 city, 15-16 highway.
So far so good, and they were less than $10 for a set! :bigthumb:
i had tried the Bosch platinums before, lasted about 3-4k miles before it started running like crap.
swapped in new champions and it was running fine.

over the years ive tried Autolites, Champions, and NGKs and the NGKs seem to make it run the best.

for plug wires i buy Summits DIY end kit for $24 or so and cut and crimp to length.

ive found that most parts store wire kits arent long enough to go over the MP aluminum valve covers.
I would just buy some Autolite, Napa, or other quality brand replacement plug wires. You're not going to gain very much, if anything, but sticking a set of $70 MSD, Taylor, INSERTYOURFAVORITEBRANDHERE 8mm, 8.5mm, or 10mm plug wires on it. Unless you want to spend that kind of money and the thought of having said products under your hood makes you sleep better at night.
:withstupid: I invested in a set of 7mm Accel wires and a MSD Blaster 2 coil...didn't seem to gain much if anything. The wires were OEM and were due for replacement, but the coil I just did to relocate it higher up from the ground.

I do keep my stock coil connector on hand, in the event that the MSD fails I can reconnect my stock coil.
doesnt anyone use ac delco plugs like me? i love mine it runs great! and they last a long time.
Aight I need to know quickly as I'm about to do it. Gap them to .035 or .040? My thing I borrowed from a friend to set the gap only goes up to .035 it's the biggest.
I gapped mine at .40, which is factory spec, and they seem to be working fine even in -7 degree weather.
You can pick up a gapper from autozone for $.99, it goes from .020 all the way to .10.
OK, here's a question for you... Anyone besides me ever had a problem with the porcelin(sp) on the Champion plugs cracking and breaking off? :cuss:

I was running Champions in my 99 5.9, #8 cylider cracked off it's porcelin and popped a hole in the piston and bent the valves...... :wall: Ok, new motor later (thinking it was a fluke) drop new Champions in the new motor, 6 months later, Truck starts runing like $hit, bucking, farting and skipping left and right, throws a check engine light. Throw the computer on it, #8 misfire. pull the plug, and low and behold, porcelin is cracked on the plug..... Pop a new set of champions in it :twak: :slap: , truck runs like a raped ape again. Last week, truck starts acting up again, throws a check engine light. Throw it back onthe computer, no codes found. :wall:

Reset the check engine light, but it still runs like $hit. Pull the plugs, and low and behold, # 8 Plug is cracked AGAIN! :cuss:

This time, I threw a set of Autolights in it because Autozone didn't have any NGK's. Truck runs great, but for how long? It just seems quite odd that # 8 keeps breaking plugs and this is on two diferent motors :shoot:

Any one else come across this?
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