Spark plug issues - help

About a week ago, during a short leisurely drive, the left front spark plug popped out of the hole. Looked in the engine bay and couldn't find it - probably fell on the road. I got a replacement plug and securely installed it.

For the second time, my left front spark plug has popped out of the hole during a drive yesterday - not sure if vibration is causing to loosen, but it's come out againn. However, this time I am having difficulty screwing it back in - as in it won't catch the grooves. Has the popping out caused the damage to the threads so that it doesn't catch? Does it need to be re-threaded? I've spent hours trying to thread it in - but no luck.

Basically you're screwed. If it popped out then the threads in the cylinder head are kaput.... But, it doesn't require a total disassembly of the head to make a repair. A kit is available that allows you to thread the cylinder head then install a collar similar to a heli-coil except it's a solid piece. That device is then screwed onto the spark plug and the plug and heli-coil like device is then screwed into the head. (use loctite) Once the device is securely fastened to the head, remove the plug and allow the loctite to dry.

Usually takes about 30 minutes to make the repair and it will be a lot easier if you remove the intake manifold.

http://www.popularmechanics.com/automotive/how_to/4212608.html

http://www.globalspec.com/FeaturedProducts/Detail/Helicoil_Spark_Plug_Thread_Repair_Kit_14mm_x_125/23773/0

what about the shavings? is it bad for the cylinder head?

Do you have to drill the hole bigger or just retap as is with the kit?

The shavings are so small that you don't have to worry about them... You simply use the supplied tap without drilling the hole larger.

I've probably repaired at least 15 or more cylinder heads by this method with absolutely no problems.

Trust me, it sure beats removing the engine from the car and then disassembling the engine to make the repair.

IT WORKS just take your time and if it's the #1 or the #3 cylinders, then it makes it much easier if your remove the intake manifold with the carburetor attached.

Use grease on the chaser tap, this will catch most of the chips and the few if any that may be missed, will blow out the exhaust when started.

I was going to post the same as the Dr.... but he beat me to it...

To add to this thread, since you're not drilling the spark plug hole to a larger diameter, the residue from the tap is usually nothing more than aluminum dust.

I know because I've repaired spark plug holes while the cylinder head was sitting on my work bench and I've seen the residue.. Believe me, it's inconsequential.

Got the spark plug thread kit - now removing the manifold...

Any how to's out there?

It's pretty simple. Remove the linkage arm from the carb. You may have to remove the fuel line and plug the opening and it all depends on if you can place the manifold and carb in an upright positon near the pulley. Next, remove the 2 nuts attached to the 8 mm studs holding the base of the intake manifold. Once loose, see if you can move the carb/manifold to the pulley area and stand the unit upright. If you can't then remove the fuel line and place the carb in an upright position on your work bench...

Follow the directions that came with the kit and you're done.

Thanks Larry - will attempt tomorrow. If all goes well, I can have a Sunday afternoon drive :)

I've gotten the manifold off - my hesitation/concern is that the angle at which I am attempting to re-thread is questionable. I there any chance I could screw this up by NOT tapping in straight into the plug hole or does the tap tool prevent that?

Never done this before and I dont want a $25 fix attempt turn into several hundred :)

Here are your choices. Remove the engine and perform the fix, remove the engine and replace the cylinder head. Look at the angle that the plug plug goes into the hole, line up your tap and go for it.

Usually, the tap is tapered on the end and will self center. You've got nothing to lose.. If it doesn't work then you're back to square 1 and will have to remove the head. Go forward with a little bit of confidence and all should work out well.

At my FLAPS yesterday I noticed a reverse tap for spark plug holes.

You insert it through the spark plug hole a bit into the cylinder and then expand it. It goes into the threads from the inside and starts tapping from there as you extract it. I think the theory is that there probably are good threads on the inside end of the hole to start the tap.

Michael, those work pretty well if you've cross threaded the spark plug hole but, in this case, the plug blew blew out of the head thus, all the threads are "toast"

In this instance, it probably needs an insert.

Wow!
Mike, where did you get the 356 logo? I'd like to have that embroidered on the back of my jacket.

Rich