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It was my fault. I made the cardinal mistake of thinking to myself, "The 7 is running great!". Not 15 seconds later as I reached the crest of the biggest, busiest bridge in the area I heard the most gawdawful noise come from the front of the car...BRAP, BRAP, BRAP...I thought I had blown a front tire and the remains were slapping the front wing every revolution. I hit the emergency flashers and got over to the slow lane. I wasn't going to stop in the middle of the bridge as that would have certainly caused an accident so I slowed and headed for the other end. As I progressed I realised it wasn't a tire but was still not certain where the BRAP, BRAP, BRAP was coming from. Had I blown out the side of the header???
When I reached the end of the bridge and popped the hood the problem was obvious. With traffic whizzing by inches from my bum I discovered the No.2 spark plug dangling on the end of it's lead. A quick check with a spark plug wrench revealed that the threads were gone. I drove the car to a nearby parking lot, BRAP, BRAP, BRAP and called the SWMBO rescue service. A quick trip to the auto parts store yielded a Heli-Coil kit which went in like a charm using only some of the 50Kg of tools in the boot (Just in case!).
An MG owner did stop by to offer help-Very good of him.
When the sealant has dried in a couple of hours I will pop back and pick up the car. Wish me luck!
Looks like I won't be getting any work that I had planned done today.

Cheers,
Rich[B)]

BTW: I put the used head on back in December. The plugs must have been overtightened at some point. I will be Heli-coiling the other 3 just in case.

1975 TR7 ACL764U

Well done Rich. I tried Heli-Coiling an alloy head, with a partially
stripped spark plug hole once. There was a bad spot in the thread
that caught the coil, & stopped it going in any further, even after
running the tap in a number of times. The coil just unwound itself.
I had to take it to a machine shop, & get it sleeved.

Tell me, how did you do it? Is it all that clean living stands you
in good stead with the boss, or do you just have to hold your mouth
right?

Hasbeen

Hasbeen,
I was really impressed by the Helicoil tap. Any helicoil I have used in the past used a special but standard looking tap. I am not sure if this type is a new development but it sure works well. The tap is a two level effort with a smaller diameter which recuts the original plug threads and uses them to pull the larger diameter tap through, which cuts the threads for the insert. There is a very sharp cutting edge in between which takes out the bulk of the metal before the insert cutter makes it's cut. I did have to break out the 1/2" ratchet but it didn't take a great deal of force to turn the tap. The most difficult part of the job was getting the angle correct.
I will be going to get the car shortly and will post a pic of the tap when I get back..

Rich

1975 TR7 ACL764U

Hi Rich,
Used the same sort of thing myself on a couple of cars in the past and if done correctly are as good as new (well nearly) Heres the type of thing for those who dont know-
http://www.timesert.com/html/sparkplug.html
We get our kit and inserts of our Snap On Tools 'man' out of his big white van full of temptation [;)]
Cheers John

LIVE LIFE A QUARTER OF A MILE AT A TIME!
1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6 WILL BE ON THE ROAD VERY SOON!
Read My Blog http://www.waringstowntr7s.co.uk/blogs/ ... hp/John215

It sure is nice to have nice crisp steel threads to screw the spark plug into. No doubt now if it's tight enough. Now only 3 more to go.
Here is a pic of the Helicoil kit. The long black tool is a punch used to expand the end of the insert, locking it in place. The kit includes inserts in 3 different lengths. The two shorter ones are shown.
The car made it home under it's own steam...or should I say. "compression", and runs the way it should.
I am now enjoying a successful recovery and repair with a Rum and Coke.[:)]

Cheers,
Rich


1975 TR7 ACL764U