FAQ: Which Spark Plugs & Ignition Wires should I use?

Jack the R wrote:

I don't have any mods, the 104's have started caking up.

NAPA didn't have 605's. I asked cause I hadn't heard of anyone running 606's.

What to you mean by caking up.
Can you provide good pic's of the spark plugs electrodes and ceramic heat sinks.?

If 104's are caking up or otherwise collecting by-products of combustion then you want to look at another heat range plug.
I don't think you should be using 104's on a non-modified engine. If you have absolutely no mod's then use a standard AC Delco plug for a stock engine or even the high mileage plugs they offer for bone stock engines. (I just read your statement about no mod's) (stock engine)
My car had over 80,000 miles on the originals before i changed them and they could have gone longer, except i was making changes to the engine.
Return the Autolites and put stock AC Delco's in a stock engine. You'll be happier and your engine will be happier.
If you do chose to try the Al's you have to gap them to 0.060" or 0.065" with a wire type feeler gauge and try them. Before the cold weather sets in again, remove and inspect. If they look good keep em, if not go back to the stock recommended AC Delco's for the winter.

Question: with a stock engine why did you put Autolite 104's in, in the first place.????
It's just not the correct heat range plug for a stock engine.
I'm questioning the 104's for my level of mod's to be honest.

104s will usually not foul in a stock engine - if driven regularly in a spirited manor. If you idle a lot, or mostly cruise (low boost conditions), they may not be appropriate for a stock set up. I've never heard of a case of this happening other than Jack.

Even so, I think Jack got quite a few miles out of those 104s, and the only thing lost was $10 for a new set of plugs. Better to start cool and work your way hotter, imo, if you are concerned with keeping knock down.

AL606 are perfectly suited for our stock engine, no need to return them.

JR,
I was under the impression that you do not drive the car on a regular basis, only occasionally.
Maybe you can clarify this.
How many miles do you drive in a years time.?

I don't disagree with Aaron about the need not to return the current plugs, but if your driving a non-modified car and not putting an excessive amount of miles on it and not driving it at it's limits all the time, then the AC Delco OEM recommended plugs will last close to 100K miles and prevent you from having to change them sooner.
That's the only point I was trying to make.
If your driving habits are different than I thought then experiment as you see fit.

AA - Thanks!

Rick W - I showed these pics a while back, you may have already commented on them -





I got 7k miles out of them. When I put them in I was planning to mod the engine, but with the expense and time I've put into adding on to the garage and remodelling the house, the car mods haven't happened.

I don't drive much, less than 2k/yr. I'm becoming a more laid back driver, would rather get all this building done before replacing a tranny.

I have 104's in mine and just recently removed all 6 for inspection and have that same mark on the side of the electrode. Strange dark spot or discoloration if that is what we can call it on all 6.
Yet the plugs were burning good all around the rest of the insulator to the point of being white, which would normally indicate a lean condition. Yet Derek took it out with the scanner and found no lean condition or KR. So I will stay with these for a couple of thousand more miles or unless I change superchargers.
I can't see the second pic well enough to comment, but the first one is eerily similar.

In the first pic, I've scraped off some of the build up.

My exhaust smells like all the fuel isn't burning, thought I'd change the plugs and see if that fixes it.

I certainly would considering what you have just said and noticed.
You obviously want to burn all the fuel/air mixture you can for efficiency.
But you knew that.

Jack the R wrote:

In the first pic, I've scraped off some of the build up.

My exhaust smells like all the fuel isn't burning, thought I'd change the plugs and see if that fixes it.

...you have no/a poisoned Cat?!?

Albertj

Rick, have you replaced your LIM gasket? Deposits on plugs #2 and #6 were my first clue that coolant was seeping into the cylinders.

Hey, it's Jack's fun time again. 606's are longer than 104's, and too long for my deep socket. The tip of the plug goes up into the hole where the male prong of the ratchet needs to be. WTF!?

IIRC someone on here told me spark plugs only need to be hand tight. I can put the socket on the plug and torque it by hand, if that' s enough torque. Want to confirm that before I continue. Spark plugs vibrating loose FTL.

Jack the R wrote:

IIRC someone on here told me spark plugs only need to be hand tight. I can put the socket on the plug and torque it by hand, if that' s enough torque. Want to confirm that before I continue. Spark plugs vibrating loose FTL.

Proper Spark Plug Torque is 20 ft. lbs. (27 Nm). Have at it He-Man

Jack the R wrote:

Hey, it's Jack's fun time again. 606's are longer than 104's, and too long for my deep socket. The tip of the plug goes up into the hole where the male prong of the ratchet needs to be. WTF!?

IIRC someone on here told me spark plugs only need to be hand tight. I can put the socket on the plug and torque it by hand, if that' s enough torque. Want to confirm that before I continue. Spark plugs vibrating loose FTL.

yeah, and some folks say you don't have to burnish hub faces before putting on new rotors... where is that torque wrench??

Albertj

It will run long enough to drive to the store and buy a longer socket.

Thanks, will look for the socket.

Jack the R wrote:

Hey, it's Jack's fun time again. 606's are longer than 104's, and too long for my deep socket. The tip of the plug goes up into the hole where the male prong of the ratchet needs to be. WTF!?

Hey now, this is a clue to my earlier question about the 100-series vs. the 600-series...

Jack, are you saying that the interior dimensions of the plugs are the same, but the exterior dimensions are different?!?

What's the firing order on the L67? There's an eensy tiny chance I got a couple wires reversed - really not likely but why not check and be sure?

Eldo - I can't find your earlier question, but I'll help if I can.

The outside part of the 606 is around 1/4" longer than the 104.

I didn't notice a difference in the interior dimensions. If you want to know badly enough I can pull one of the 606's back out and get a picture of the two together.

Jack the R wrote:

The outside part of the 606 is around 1/4" longer than the 104.

I didn't notice a difference in the interior dimensions. If you want to know badly enough I can pull one of the 606's back out and get a picture of the two together.

I think you've hit upon it! The longer the outside of the insulator, the more heat it is going to suck from the tip of the plug. However, if you could pull one of the easy plugs from the front of the motor, it would be very helpful in answering this eternal question...

EDIT: AA's right, I wrote the insulator theory back-asswards...

Sure, I'll pull a plug and get a comparison pic, but - isn't the 606 the hotter plug? It's also the longer plug, which suggests the extra length of the ceramic part has something to do with making it hotter instead of cooler.

I think Eldo's question was answered on page 10 of this thread.

Of course the 606 is going to be longer than a 104. It is also a little longer than a 605, which is a little longer than a 104. A 104 is longer than a 103. The length is a result of having more or less insulator material, which keeps more or less heat in the cylinder, making it a "hotter" or "cooler" range plug. More insulator = hotter range.

The length of the plug (or insulator) corresponds to the last number (heat range) of the plug's code. 6 is stock (long), 5 is 1 range cooler (shorter), 4 is 2 ranges cooler (even shorter), etc..

So nobody knows the firing order for the L67?

Jack the R wrote:

So nobody knows the firing order for the L67?

165432 = Firing Order

2 4 6 - rear bank of cylinders
1 3 5 - front bank of cylinders

Jack the R wrote:

So nobody knows the firing order for the L67?

RTFM... J/K Jack, I'm sure you were just looking for some quick feedback.

Or, Google is your friend.

Jack asked for firing order, but Rick was nice enough to include cylinder location.

He could have been a jerk and said: "1-6-5-4-3-2"

Rick - thanks, everything was o.k. but it's good to know for sure.

O.k I have a set of 104's in my possession and want to swap them out for my stockers and a new set of wires too.Question is,are 104's too cold for a stock engine??I do get on it pretty frequently and have read that 104's are suggested for anything at 6-12 psi of boost,and seeing as how our engines make 6-8 psi stock I figured I'd be safe as long as I "clean em out" with a few on ramp bursts of W.O.T. Am I correct in this??I don't want to foul them up and have to change them again anytime sooner than 20k-ish.I am geting ready to do this tonight,so sooner the better as far as a reply goes...thanks,Don