The Mustang Forum for Track & Racing Enthusiasts

Taking your Mustang to an open track/HPDE event for the first time? Do you race competitively? This forum is for you! Log in to remove most ads.

  • Welcome to the Ford Mustang forum built for owners of the Mustang GT350, BOSS 302, GT500, and all other S550, S197, SN95, Fox Body and older Mustangs set up for open track days, road racing, and/or autocross. Join our forum, interact with others, share your build, and help us strengthen this community!

S197 spark plug changing in mod motors

SO, cruising around the different sites, it seems like a lot of people are having problems with their mod motors and spark plugs, from the old SOHC 4.6 to the newer DOHC. So.. apparently having been one of the few people on the planet who has never had a plug blow out, stripped the threads or had to use a threadcert to put plugs back in, I consider myself somewhat of an authority on this.
I'm going to assume that those later model cars that have not had spark plug issues is primarily because they are still so new that they haven't been changed yet. Which leads us to the first point.
You have to actually change spark plugs once in awhile.. modern cars can go 150K plus miles without a plug change, but that doesn't mean you should. Since we are talking high performance engines, (or in this case, the truck I use to haul the car with the high performance engine) it pays to pull the plugs at least every 50K miles and have a look. Back in the day, plug reading was an art, you actually tuned by them, today, not so much because of all the electronics. But you say.. if the plugs aren't worn out, why change them, well just change them, and scrounge up an old school plug cleaner, clean the old ones, and put them back in later. Or, put them back in right now.. it doesn't matter. Once you start using one of these you will use them on everything, your hot rod, lawnmowers, chain saws..etc. A source is listed below.
Air Spark Plug Cleaner (harborfreight.com)

Point 2
Ford has built a plug where the threads descend into the combustion chamber.. while there are "problem solver" plugs available that fix that, I don't know of any that say Motorcraft or NGK on them, and the ones that do exist are exponentially expensive. Guys have tried warming up the engines first, doing plugs when the engine is cold.. whatever. this is what has worked for me. First, I prefer the engine to be cold, because I hate getting burned, I then go in, remove the coil packs (more on this later) and start to remove the plug. In almost EVERY case, you will start to loosen it, and it will bind up. This is where the built up funk from the combustion chamber is on the threads, if you continue to force the plug out, you will drag this through the head, destroying the threads, .. so stop. All you need is maybe a full thread loose, then go find some PB Blaster, and spray it into the plug cave. Go have coffee, go eat lunch, call your girlfriend, get on TMO, just let it sit for at least a couple of hours. When you come back, blow out the plug cave with an air hose to get rid of the Blaster, leaves, and whatever else might run into the combustion chamber. go ahead and start removing the plugs, most likely, you will find they will start to come out, then bind again, this is normal, screw the plug back in and out a few threads and you will find the plug will come out without damaging the threads. I'm not sure if the Blaster dissolves the funk or what, but it at least weakens it so the plugs can come out. I then fish the old plugs out with a magnet.

8w8Fqd6l.jpg

Point 3
Once the plugs are out, gap the new ones, I then run them in with a piece of fuel line, I do this for a couple of reasons, one is that since you can't really see the threads, and are doing it by feel, the rubber hose will slip instead of forcing the plug into the hole when it's cross threaded, so it acts like a safety, in that regard, it also gives you a lot of reach to start the threads, and can bend around the misc objects in the engine bay. By using the rubber hose, you can feel the plugs thread all the way into the taper of the head.. At that point, you only need to tighten the plugs, I'm not sure what the torque value is, and good luck at getting a torque wrench into some of the areas, so I just "tighten" them, remember they are tapered seat plugs, they just need to be tight, there's no reason to twist them out of the engine bay.

Point4
Remember when you pulled the coils off and left half of them in the plug cave stuck on the end of the plug?, What I do, is, I use a bit of white grease on the plug boot. I tried the dialectric stuff, but it crystalizes and IMO is worse than nothing. I don't go nuts with it, but it keeps the coil pack/plug boot intact when removing them.

UkdWT64l.jpg

And just for the record.. it's really no fun to work on the daily driver, or tow vehicle, but nobody wants to get stuck on the side of the road in Resume Speed, Arkansas either. My 2010 Ford F150, 3 valve with 177K miles on it was due for timing chains. Well, actually not, it wasn't making any noise, but I just felt sorry for it, so I put a set in. (my back is trashed so I have a friend that's a Ford master tech do it for me, but I have had plenty of practice). I change oil every 3K to 3500 miles, I use Pennzoil High Mileage in 10w 40. I also dump a pint of Lucas oil stabilizer in when I do it. The timing chains would've gone another 30K miles, no issue, they were remarkably well preserved. Also, when I replaced them I used factory Ford parts, not some Dorman junk.
I also replaced the oil pump, and contrary to popular belief, you don't need to drop the pan on a 4.6 to do this, you can sneak a flex wrench (8mm I think)under the pump and unbolt the pickup, let it drop into the pan (it won't go far) , bolt up the new pump, and fish the pickup out an reattach it to the new pump. If you happen to drop the bolt into the pan, just fish it out with a magnet. Disconnect the sensor on the balancer, crank the engine to prime the pump (I filled the pump as best I could with oil to begin with) once you have oil pressure reconnect the sensor and it will start right away. I think you would agree that the parts look great, especially for 175K plus miles.

IKJWKDUl.jpg



Lucas Oil Products Heavy Duty Oil Stabilizer (1 qt.) 10001: Advance Auto Parts


Point 5, When you remove the wiring clip from the coils be very careful, where the coil clip meets the actual coil pack is very weak, the heat only makes this worse. There is a clip on the wiring harness that must be depressed in order for it to be removed. If it doesn't come off, push it back on, trigger the clip and try it again. Some times this coil/ clip interface dies on it's own, but here's no need to force the issue. In this pic, is the weapon that I use to defeat the clip (not shown) it is pointing at the weak spot in the coil pack.

LoTiYLEl.jpg
 
Last edited:
3,594
3,396
Good points & I will add one, use a spark plug socket
Yeah, but I've had a lot of issues using one, don't get me wrong, I'd like to use one, but when the little rubber washer stays on the plug instead of staying in the socket, it gets aggravating. Maybe I need to pony up for a decent set of Snap On sockets and leave the brand X at Home Depot
 

xr7

TMO Addict?
416
407
Exp. Type
Autocross
Exp. Level
5-10 Years
Minnesota
Yea, if you are changing plugs regularly a quality plug socket is a must, especially when you are doing plugs way done in a well like these Coyotes. I would usually pack a piece of shop rag between the extension and the socket hole so it would pull of the plug. Luckily it was pretty rare that I was changing plugs on that type of engine.
P.S. I have one of those Harbor Freight plug cleaners. Purchased a looooong time ago. Snowmobiles, snow blowers and a Kawasaki 500 triple 2-stroke that like clean plugs, often.
 
Last edited:

xr7

TMO Addict?
416
407
Exp. Type
Autocross
Exp. Level
5-10 Years
Minnesota
Anybody got a picture of a Coyote combustion chamber with the sparkplug installed? I'm thinking you could put the plugs in a lathe and cut down the excess threads?
Ford does seem to have problems figuring this out. First we had about for threads so plugs blew out, then they came out with that skinny two piece plug disaster. Somebody needed to slap mister sparkplug engineer's knuckles with a slide ruler.
 

Grant 302

basic and well known psychic
People who strip threads and monkey stuff up often probably shouldn’t be changing their own plugs.

I’ve removed countless plugs from aluminum heads. Hot, cold, warm, two stroke, four stroke, flat head and most cylinder counts you can think of including 5. Mostly for the tuning aspect.

I’ve never stripped a plug.

I always use a plug socket.

Never had a problem. Even with the notorious 2V modulars.

I use anti-seize on the threads. Just a bit. I’ve used both stick and tube types. Yeah, don’t put it on the conical seat. Or you would likely over-torque.

My guess...and it’s a complete guess, but I think most plug thread problems are from people who cross thread. Like I said, I don’t know and can’t know what the mechanically challenged do.

I use the socket to do the install on Modulars. Using my fingers on the end of the extension. Simple.

I’ve used Craftman and cheapies from misc parts stores. Main thing is to replace when or before the rubber insert completely wears out. Keep that one as spare. Or use it to throw at other racers in the pits.
 
3,594
3,396
People who strip threads and monkey stuff up often probably shouldn’t be changing their own plugs.

I’ve removed countless plugs from aluminum heads. Hot, cold, warm, two stroke, four stroke, flat head and most cylinder counts you can think of including 5. Mostly for the tuning aspect.

I’ve never stripped a plug.

I always use a plug socket.

Never had a problem. Even with the notorious 2V modulars.

I use anti-seize on the threads. Just a bit. I’ve used both stick and tube types. Yeah, don’t put it on the conical seat. Or you would likely over-torque.

My guess...and it’s a complete guess, but I think most plug thread problems are from people who cross thread. Like I said, I don’t know and can’t know what the mechanically challenged do.

I use the socket to do the install on Modulars. Using my fingers on the end of the extension. Simple.

I’ve used Craftman and cheapies from misc parts stores. Main thing is to replace when or before the rubber insert completely wears out. Keep that one as spare. Or use it to throw at other racers in the pits.

I think the big issue is that guys just ream them out of the plug hole even though they don't want to come out because of the crud on the end of the plug. It really is a problem when those threads project into the combustion chamber. I've started to remove countless plugs, only to find they bind, I don't force them out.
 

Norm Peterson

Corner Barstool Sitter
930
702
Exp. Type
HPDE
Exp. Level
5-10 Years
a few miles east of Philly
I think the big issue is that guys just ream them out of the plug hole even though they don't want to come out because of the crud on the end of the plug. It really is a problem when those threads project into the combustion chamber. I've started to remove countless plugs, only to find they bind, I don't force them out.
The difference between a machinist or a mechanic and a wrench-turner, no? People in that last group aren't allowed anywhere near my tap set for much the same reason.


Norm
 

Grant 302

basic and well known psychic
I think the big issue is that guys just ream them out of the plug hole even though they don't want to come out because of the crud on the end of the plug. It really is a problem when those threads project into the combustion chamber. I've started to remove countless plugs, only to find they bind, I don't force them out.
Seriously, I don’t know how that’s possible. I’ve never ‘forced’ out a plug either. And I can’t say I’ve ever thought carbon or combustion residue was the issue. But water vapor from combustion and the dissimilar metals of the aluminum head and spark plug cause galvanic corrosion at the threads. So aside from the intial torque to ‘crack’ the plug loose, there should be no special effort to get the plug out. It should come out without using a wrench. Just using your fingers on the extension.

I think the fubar mistakes are made putting the plug back in.

The difference between a machinist or a mechanic and a wrench-turner, no? People in that last group aren't allowed anywhere near my tap set for much the same reason.

So a ‘machinist’ is a guy who ‘fixes’ all his mistakes with a tap? 🙃
 
3,594
3,396
Seriously, I don’t know how that’s possible. I’ve never ‘forced’ out a plug either. And I can’t say I’ve ever thought carbon or combustion residue was the issue. But water vapor from combustion and the dissimilar metals of the aluminum head and spark plug cause galvanic corrosion at the threads. So aside from the intial torque to ‘crack’ the plug loose, there should be no special effort to get the plug out. It should come out without using a wrench. Just using your fingers on the extension.

I think the fubar mistakes are made putting the plug back in.



So a ‘machinist’ is a guy who ‘fixes’ all his mistakes with a tap? 🙃

Well I guess you change plugs a lot, over maintaining is definitely a way to prevent the problem, I've had very little issue on my performance cars, but when I first pulled the plugs on my 99 GT, my 01 Cobra and my 2010 F150, everyone one of them sent up red flags.
 

Grant 302

basic and well known psychic
Well I guess you change plugs a lot, over maintaining is definitely a way to prevent the problem, I've had very little issue on my performance cars, but when I first pulled the plugs on my 99 GT, my 01 Cobra and my 2010 F150, everyone one of them sent up red flags.
Well not so much anymore, but back when I was drag racing and helping a lot of friends work on theirs...and when doing my own tuning in the 2V, and the other 2V plus the Terminator...and then further back in my 2-stroke/motorcycle days. I’ve only cracked into the coyotes for a peek.

But I don’t just mean MY engines. I mean I’ve never been ‘afraid’ to change the plugs on aluminum heads on other people’s cars. I suppose that’s why I’ve helped many do it. And wouldn’t hesitate to do it today. It’s not rocket science. My plug changing stuff is in the same yellow craftsman toolbox with the black lid circa ‘80s vintage.

Just don’t ask me to do it on an F-body...I’m not squeezing under that cowl for anybody.
 

xr7

TMO Addict?
416
407
Exp. Type
Autocross
Exp. Level
5-10 Years
Minnesota
My only experience with problem sparkplugs were with the Ford engines, had a few that blew plugs out of the head, 5.4L engines. I suspect the problem here may have been improper torque from the factory. Problem may have been solved by retorquing plug shortly after being put in service. These engines also had about four threads in the head for the plug so not much margin for error.
The other were the real skinny plug they used on the 3 valve head. Those were best removed by crack it loose, liberal use of PB Blaster and come back in an hour and see if they move or need another shot. The problem was two fold, carbon locking the plug in and the original plug is two piece! You know there is a problem when Ford has special tools and procedures developed for removing broken plugs. Lastly Ford also changed the 3 valve cylinder head during 2008 production, they went back to a conventional plug.
One of Fords "Better Ideas"
ford_motorcraft_pzt_2fe_spark_plug.jpg
 
Last edited:
3,594
3,396
My only experience with problem sparkplugs were with the Ford engines, had a few that blew plugs out of the head, 5.4L engines. I suspect the problem here may have been improper torque from the factory. Problem may have been solved by retorquing plug shortly after being put in service. These engines also had about four threads in the head for the plug so not much margin for error.
The other were the real skinny plug they used on the 3 valve head. Those were best removed by crack in loose, liberal use of PB Blaster and come back in an hour and see if they move or need another shot. The problem was two fold, carbon locking the plug in and the original plug is two piece! You know there is a problem when Ford has special tools and procedures developed for removing broken plugs. Lastly Ford also changed the 3 valve cylinder head during 2008 production, they went back to a conventional plug.
One of Fords "Better Ideas"
View attachment 63162

Looked good on paper though..
 

TMO Supporting Vendors

Top