Time Sert is the BEST fix for blown spark plugs, and in your case, because you tried the "cheap/worst" fix that they recommended at the parts store (same as I did... was not aware of "better" or "best" fixes that were available), you now HAVE to use an oversize insert... and Time Sert's 5600 is the best of them, and a permanent repair. You did good!
Now for your "open valve" detector. If you go to Wise Auto Tools,
http://wiseautotools.com/calvan-cv-389-4000-leak-tester-to-determine-valves-are-closed/, they have a very simple, "inexpensive" detector from Calvan (SKU 389-4000, $21.99). Basically a valve, hose, and rubber stopper that fits in the spark plug bore hole... blow in a little air pressure, and when you rotate the engine to where the valves in that cylinder are fully closed, pressure builds up and pops the stopper out of the bore. Then all you have to do is check to see that the piston is not at the top, and do your repair.
Good luck.
First of all, I didn't put the helicoil insert in this Explorer. That was done by the prior owner who didn't tell me that it had a prior repair. So I bought it with the prior repair already having been made although I wasn't told about that.
I threatened to sue him (I'm a lawyer) for failure to disclose that, but decided not to do it because at the end of the day he actually did me a favor because (as you say) the only alternative left was the Time-Sert 5600 kit, which is pretty clearly the best repair for this problem.
Obviously, a helicoil won't work.
So although he should have disclosed that to me, as well as another problem I found out about later (as per below), I really didn't have any damages to speak of because the Time-Sert repair is the way to go.
As far as that repair goes, I agree that it's likely a "permanent repair" (I certainly hope so) although I've only put a bit over 200 miles on the vehicle since I made the repair. But if you look at this post -
http://www.ford-trucks.com/forums/991189-spark-plug-thread-repair-with-photos.html
you'll see that as of his last update on pg 3 he's gone 50,000 miles and the repair is still holding.
As far as my original question, I used the notch on the crank pulley, the TDC pointer on the block and the firing order, together with my homemade hose and rubber stopper tool and the position of cylinder
#7 , to determine when both valves were closed and the piston was near the bottom of it's run.
My homemade tool, which Wise Tools sells for 20 bucks, cost me about $2.00 (for the rubber stopper and the hose). I drilled a hole in the rubber stopper to fit a piece of new brake line that I had left over, and an old valve stem to connect the hose to my compressor. Worked like a charm.
I just used a wooden dowl down the spark plug hole to determine piston position up or down.
Beware that when the piston is all the way down on the power stroke the valves are not fully closed. The exhaust valve has already opened somewhat, tho perhaps not enough to matter. So you want to lower as far down as it will go without the valves opening at all. That requires turning the crank by hand quite a bit, but it's easy enough to do if you remove the bolts that secure the lower half of the fan shroud and move it out of the way (it looks virtually impossible to actually REMOVE that part of the shroud, so just move it around to get better access to the crank nut)
Another thing to be careful about is making sure that the tools involved in the Time-Sert repair don't drop down onto the piston. I used some tape wrapped around the tools at the appropriate spot to prevent them from going far enough down to hit the piston. Just wrap enough tape around the tool so that the taped spot is too large to go through the hole you're working on.
That proved quite valuable when I used the final driver which almost came loose from the "wrench" because the set screw that secures it into the wrench had come loose. You drive both driver tools THROUGH the inserts and thus you have to re-thread them back into the insert to remove them from the cylinder. That can be a bit tricky and in fiddling around trying to catch the threads of the insert the tool can easily come loose and drop off into the cylinder. If there isn't something to stop it, it will go on down until it hits the piston and could possibly put a hole in the piston. I used painters tape for the tape.
The other thing I did was to use the rubber boot from a spark plug coil which I taped to my vacuum cleaner tool to help in sucking out the aluminum bits that are created in making the repair. I added a straw to the rig later so that it would go all the way down to the piston and hopefully get all of the bits out, tho' I think there's really no way to get ALL of them out.
Still, they are tiny aluminum bits that likely burn up or blow out the exhaust valve pretty quickly, so hopefully no harm done.
Now that the weather has turned chilly here in NJ, I found out that this Explorer ALSO has the dreaded "blend door" problem.
I'll post a new thread on that because this post is already too long.
