Blew a spark plug out - how driveable is it?

Otter74 · 06-15-2019, 06:40 PM

I was having grand day driving in the mountains of West Virginia when early this evening the engine spit out the #6 plug. Threads in the head are screwed - the plug will seem to thread in but it never bottoms out and you can then just pull it out. So I have two questions while I figure out a game plan for tomorrow:

1) is the head permanently fixable - TimeSert or something else - or is any fix u,timately temporary and I'll have to replace the head?

2) is the car driveable long distances? Obviously it's not getting spark to #6 and I unplugged the injector so it's not getting fuel. The cylinder is still getting lubricated. So the fundamentals seem there. The engine is obviously imbalanced but this doesn't seem like a big issue. Not sure if the absence of heat on #6 only is an issue. I drove the car about 25 miles to my destination for the evening, and I'm ok driving it 90 miles to Pittsburgh tomorrow. in a perfect world, I'd nurse it home the 500 miles to Chicago. Sure it's slow and loud as hell, but all I'm concerned about is damaging the engine.

It's either get it home (renting a truck and trailer is going to cost a fortune, so I doubt I'll do that) myself or leave it in Pittsburgh, have someone fix it there (I've got a place to store the ar as long as needed), fly home and fly back later to get it.

Thoughts?

Trackrash · Trackrash's Garage

Drive it? No way. Fixing a head is one thing. A new motor is another....

Otter74 · 06-15-2019, 07:29 PM

Quote:

Originally Posted by Trackrash

Drive it? No way. Fixing a head is one thing. A new motor is another....

What is driving it as-is going to do to the motor? I'm not saying it won't do anything, because I'm not sure. I'm one of those types that likes to understand everything

eastbay · 06-15-2019, 08:09 PM

Do an Internet search on plug saver

ClickClickBoom · ClickClickBoom's Garage

https://www.toolsid.com/heli-coil/heli-coil-save-a-thread-spark-plug-repair-kits-22564871.html?gclid=Cj0KCQjwrpLoBRD_ARIsAJd0BIUmbV rvJi5TUDvdhZIw53UED_FiT_lG1CVXRlVgAF87OSc30eg7JfAa AvV0EALw_wcB

Any halfway decent auto supply will have one. Get a tub of grease to catch the chips, follow the instructions.

https://axleaddict.com/auto-repair/Blow-out-Spark-Plug-Repair-Using-the-Save-A-Thread-Heli-Coil-Repair-Kit-Ford-Crown-Victoria

Sboxin · Sboxin's Garage

. . . been there . . . Columbus to Albany . . .
Free advice - Uhaul truck and trailer - do not leave your car . . . unless you have very trustworthy friends in Pittsburg . . .

Also, if a plug blew out - what about the others ? It might be time for more engine work/maintenance ?

Wish you the best,
Regards,

Walt Fricke · 06-15-2019, 10:39 PM

I drove a VW bug from the middle of Mexico to Denver on 3 cylinders once. The tip of a valve pulled off, the valve fell part way in, got smacked back and the stem bent, which kept the valve up high enough that it didn't hit. I pulled the rocker, finished the Carrera Panamericana race, and drove home from the border. I don't recall if I pulled the spark plug, but upon disassembly I didn't find any additional damage.

I once, at an autocross, miswired my SC's distributor. Running on 4 cylinders wasn't super fast, but it ran. These engines have enough power on five for sure.

Is it possible to tap (is that all that is required for a plug hole saver, or do you need to drill first?) this in the car? #6 is just about as inconvenient as #4. I am dubious.

I would think driving without a plug in a cylinder would cause problems with the mixture - you have a path through the intake runner to the air box, and the air which gets up into the box that way is going to lean the mixture quite a lot, like any other air leak in the intake on the cylinder side of the air measuring system over on the right side of the intake. But maybe not?

One option is paying for some professional assistance, or at least opinion.

Having a shop help with repairs, temporary or permanent, may be the best approach. Sewickley in Pittsburg is the closest I can think of offhand, and Duane Smith knows these cars: dsmith@sewickleycars.com. Steinel's, a bit SE of Cleveland, is a good Porsche shop also. Someone may know of a better, closer, place. I just know these guys from race officiating.

Like you, I'd like something more specific than "just don't drive it any more." That may be exactly the right advice, but some explanation of what and how further harm is going to occur would be helpful.

All I can think of offhand is maybe a lean mixture, and you could do something about that by seeing if you could remove the intake runner for #6 and blocking its connection to the air box. Though perhaps removing the #6 intake rocker would be easier and maybe better - there is a whole lot of stuff over by #5 and 6 to get in your way getting to that runner.

As long as the engine compartment isn't very dusty, maybe you'd not suck much dusty air into that cylinder?

The engine is going to be out of balance, but you can keep the revs down to help with that. A chance of twisting the crank would not be on my list of worries.

You say you disconnected the injector. Good move, for sure, but where is the continuous (CIS injection) fuel flowing to? Did you find a way of plugging the line from the fuel distributor?

But you really should check out the U-Haul option, so you have some idea of the relative costs of things. I have trouble imagining repairing that particular spark plug hole without dropping the engine.

Checking the other plugs sounds like a good idea, considering. I can think of two potential reasons for this one being spit out: One is that it wasn't tightened on installation, but that would allow you to screw it back in (with maybe just the top few head threads broken off)and you say it just spins. The other is that someone along the line cross threaded things. When you have the engine out (at least eventually), pulling all the plugs to check for thread integrity might be in order.

Are you a PCA member? From time to time Porsche owners caught in a pickle get ahold of someone from the local PCA region to see what help can be had. You never know - maybe someone with a trailer might take your car at least to a local shop.

SCadaddle · 06-15-2019, 11:26 PM

Quote:

Originally Posted by ClickClickBoom

https://www.toolsid.com/heli-coil/heli-coil-save-a-thread-spark-plug-repair-kits-22564871.html?gclid=Cj0KCQjwrpLoBRD_ARIsAJd0BIUmbV rvJi5TUDvdhZIw53UED_FiT_lG1CVXRlVgAF87OSc30eg7JfAa AvV0EALw_wcB

Any halfway decent auto supply will have one. Get a tub of grease to catch the chips, follow the instructions.

https://axleaddict.com/auto-repair/Blow-out-Spark-Plug-Repair-Using-the-Save-A-Thread-Heli-Coil-Repair-Kit-Ford-Crown-Victoria

Holy Smoke! That dude in the video must have torqued that plug and insert to 200 ft. lbs. with a 1/2" ratchet setup!

Otter74 · 01:43 AM

Walt, thanks for that detailed note.

I forgot to mention that the car is running on a Megasquirt for fuel and ignition (Ford EDIS), so no CIS.

The engine compartment is a ton les crowded than a stock one, but I can't imagine tapping and threading anything with the engine in the car unless you had, I dunno, nanobots. Or ninja skills. Access is a PITA even though you can at least see the VC.

And I am very fortunate that I do have someone that I would 100% trust leaving the car with. It would sit with the owners Triumph TR4, Ferrari 456, old Packard and I don't remember what else. For working on it, the people from there recommended Charlie Hsu (sp?) first if I'm patient and then a shop named I think German Motor Works or soemthing like that (don't have it written down)

I think it might be cheaper or easier to have a transporter take it home than to rent a U haul.

As for why the plug blew out, that's the mystery. This actually happened to me once before either last summer or the fall before. I was in New Glarus, WI that time and didn't have tools with me but was within a short walk of a farm supply place so I just walked down, bought a few tools and screwed the plug back in. Thought it was bizarre but didn't think much of it again. At the time I figured it was loose and unscrewed itself, which doesn't make a lot of sense in retrospect but then again I screwed it back in and there it sat for 5-10k more miles....until last week when I put new plugs in. Felt OK when I threaded it in but obviously the threads were damaged and 800 miles later, boom. It's possible the threads were damaged when the top,end was rebuilt by the PO in 2013.

Flat6pac · 06-16-2019, 02:37 AM

I would think the damage would be in just the top couple threads
You’re not going to blow a plug out of a dozen threads.
Grind done the first couple threads on the spark plug so to lead you past the damaged threads
You should get the plug in and working.
Bruce

Dave Kost · Dave Kost's Garage

Otter,

Sent you a PM with my contact info.

Let me know if I can help.

Dave

Quote:

Originally Posted by Otter74

Walt, thanks for that detailed note.

I forgot to mention that the car is running on a Megasquirt for fuel and ignition (Ford EDIS), so no CIS.

The engine compartment is a ton les crowded than a stock one, but I can't imagine tapping and threading anything with the engine in the car unless you had, I dunno, nanobots. Or ninja skills. Access is a PITA even though you can at least see the VC.

And I am very fortunate that I do have someone that I would 100% trust leaving the car with. It would sit with the owners Triumph TR4, Ferrari 456, old Packard and I don't remember what else. For working on it, the people from there recommended Charlie Hsu (sp?) first if I'm patient and then a shop named I think German Motor Works or soemthing like that (don't have it written down)

I think it might be cheaper or easier to have a transporter take it home than to rent a U haul.

As for why the plug blew out, that's the mystery. This actually happened to me once before either last summer or the fall before. I was in New Glarus, WI that time and didn't have tools with me but was within a short walk of a farm supply place so I just walked down, bought a few tools and screwed the plug back in. Thought it was bizarre but didn't think much of it again. At the time I figured it was loose and unscrewed itself, which doesn't make a lot of sense in retrospect but then again I screwed it back in and there it sat for 5-10k more miles....until last week when I put new plugs in. Felt OK when I threaded it in but obviously the threads were damaged and 800 miles later, boom. It's possible the threads were damaged when the top,end was rebuilt by the PO in 2013.

manbridge 74 · 06-16-2019, 05:25 AM

Put the plug and tool back in. Fashion a metal strap between valve cover studs to fit over spark pug tool to hold it all together. Drive home and repair correctly.

porsche930dude · porsche930dude's Garage

maybe you can use a longer plug with added washers to get a few more threads of engagement. I think id just wedge or strap it in there somehow.

manbridge 74 · 06-16-2019, 06:39 AM

Yeah, maybe a socket and extension that is just proud of v/c surface would be easier to hold down.

Otter74 · 06-17-2019, 10:24 AM

I'd like to thank in particular Walt Fricke for helpful posts and Dave Kost for offering another place to leave the car if I needed it.

After an uneventful drive from Davis, WV back to Pittsburgh and booking myself a one-way on Southwest for Sunday evening in case I needed it, I ultimately decided to drive it home. Leaving the car would have enforced a return for Grand Prix weekend

(which I'll likely do anyway) and freed up a garage space at home for 4-5 weeks to allow me to do some maintenance on my normal cars without kicking something out of the garage, but in the end I concluded the only risk of driving it home was FOD in the cylinder and that that risk was very low, below my threshold for accepting it.

There was no way anything was getting threaded in that plug hole - yes, all 12 threads are stripped. I may not be able to see it, but I can feel it. The drive home was merely loud. I kept the revs down but otherwise drove normally.

In a perfect world I dream of being able to TimeSert (or whatever) the plug hole without taking the head off, but I'm not willing to bet on the odds that cutting lube will hold all of the shavings from cutting new threads and keep them out of the cylinder. So it looks like once the engine is out, the head's coming off and I'll be asking new questions

David

pampadori · pampadori's Garage

you might be surprised how well a smartphone can fit down near the spark plug holes and the quality of the imaging with the flash on. Could you take a video to see the condition of the threads?

pmax · pmax's Garage

Quote:

Originally Posted by Otter74

After an uneventful drive from Davis, WV back to Pittsburgh and booking myself a one-way on Southwest for Sunday evening in case I needed it, I ultimately decided to drive it home.
...
in the end I concluded the only risk of driving it home was FOD in the cylinder and that that risk was very low, below my threshold for accepting it.

500 miles on 5 cylinders, must be a recent record of some kind. Curious how much oil got spat out on the covers after 500 miles ?

Crud getting into the cylinder with the open plug hole is a good point. Hopefully the oil cooler area was relatively clean.

Otter74 · 06-17-2019, 11:43 AM

Quote:

Originally Posted by pampadori

you might be surprised how well a smartphone can fit down near the spark plug holes and the quality of the imaging with the flash on. Could you take a video to see the condition of the threads?

Good idea - I hadn't thought of that. May not have done me much good at the time as I only had my iPhone 5S on me and the camera isn't that great and there wasn't a lot of light. But my work Samsung has an excellent camera - I'll try it tonight.

Quote:

Originally Posted by pmax

500 miles on 5 cylinders, must be a recent record of some kind. Curious how much oil got spat out on the covers after 500 miles ?

Crud getting into the cylinder with the open plug hole is a good point. Hopefully the oil cooler area was relatively clean.

I had a look under the engine lid in Pittsburgh, and it looked normal then in terms of oil. I'll look again when I get home, but I'm betting nothing significant. And it is pretty clean in there.

Walt Fricke · 06-17-2019, 01:29 PM

There must be some ways of adding suspenders to well greased cutting tools when preparing the hole for an insert.

One way guys change valve springs on an intact motor is to shove a bunch of string down the plug hole, and then bring the top of that piston up until it presses the string stuff against the valve heads. Of course, you leave an end of the string out so you can get it back out.

If you have a hemostat, or a grabber, you could probably reliably get the in through the plug hole to retrieve it. My notion is that you could grease the string liberally, and extracting it might get any chips which got in back out.

Nobody is going purposely to put aluminum chips into a combustion chamber. But a few small ones seem unlikely to cause any serious harm. I once decided to attach carburetor air horns through the air filter base with slot head screws rather than the studs and nuts which were usual for the purpose. The screws backed on the track eventually, the horns moved, and some small steel screws got sucked into various combustion chambers. I could hear when it happened as my wife was taking the final few laps of a race.

Some of the screws were spit out the exhaust. Some were embedded in the head or a piston. All this cleaned up reasonably well (no valve damage)though hardly perfect internal cosmetics.

While drilling/threading you might be able to blow air in the intake so it would come out the plug hole while you worked. Having a bore scope for use when done would be useful - you could use it to see what might have gotten into the combustion chamber. The grease on such chips might allow you to use the scope to fetch them out.

And someone who has done this on an intact engine may read of your problem and have better practical advice.

I'm assuming pulling the engine so you don't have to work while a pretzel is in order here. If you can put the engine up on a stand, you can rotate it so the plug hole faces straight down. A bit more awkward working on it, but you'd have gravity on your side relative to chips.

We are often cautioned not to put anti-seize on the plug threads, sometimes by guys with darn good credentials. But I'm more afraid of damaging the threads in the heads than I am of the plug not having good electrical connectivity to the engine, so I have always used anti-seize on the plugs for my VW and Porsche air cooled, aluminum head, motors.

carreradpt · carreradpt's Garage

Otter74. I also blew the plug in #6 a handful of years ago a 100 miles from home. I was able to thread it back in and made it home. My neighbor had a scope and the threads were about shot. Time for a top end at 161K. #6 was time serted. That was about 35K miles ago.

I figured somehow I missed torqueing that plug snugly. You can bet I double check them pups now. Good luck on yours.