A couple weeks ago, the car started running rough all of a sudden. Found that a wire was off No 1 plug, AND the plug was loose. Last had them out for a valve adjust begining of July, right before a 360 mile round trip to the sierras, with no issue.

Anyhow, pulled the plug, and put it back in, trying to feel for cross threading evidence, but it felt fine. Car ran great again.

Now, today, on a 80 mile round trip, it loosened up not once, but twice.

What could be causing this?

What torque value did you use?

I usually just get them hand tight, then give them about a 1/4 turn (hard).

What should I use for a torque value?

It may be time for a plug fix kit

Only about 8k on rebuilt heads. Holes were welded up an retapped.

That being said, I have heard the inserts are not that bad. Seem to recall hearing that 356 racers went with inserts because of all the pulling of plugs and re-installing.

Who sells the kits?

Uh, before you freak out here, get a torque wrench and tighten them properly to the proper torque. Hand tight and a quarter turn ain't gonna cut it. I'm on my phone so don't have access to the torque spec. someone will be along to let you know what it is.

I think it's 15 ft. pounds

edit: threads are prob stretched by now.......

Ok, torquing to 18. Feels solid. Will check torque when cold, and see what happens.

You might wanna check them all while your at it. How much more did it go than the quarter turn?

Actually, probably about a quarter turn.

Well, its still backing out, so I am certain my threads are F'd or I have got a crack developing. Time to drop the engine.

Both heads were rebuilt once, with three out of 4 plug holes getting welded due to cracks. It will be interesting to see if this is the one hole that did not have a crack.

I have access to a pair of 1.8 heads, and seem to recall they are a better design. Have them gone through is an option, I suppose, if there are advantages that anyone can point out. Of course, then I need to source new weber manifolds.

Soooooo.....which way to go?

Pull head, have hole repaired, reinstal?

Have 1.8 heads gone through, swap out?

Any other recommended "while I am in there" tasks?

1.8 head need the plug moved, larger valves installed with new seats, and intake manifold studs removed, welded and moved to use as 2.0 liter heads.

I would pull the head , fix the plug with a threaded insert, put it back on and drive it.

Rich

Don't put anything past the Time Serts. Especially on a low-torque place like a SP hole. They make kits especially for them. Save yourself some money and do it that way. Might even do the other one while its out? John at Aircooled.net even rents Time Sert kits for a month at a time and the serts themselves are only a dollar or two a piece.