[ski_shop_cam]

Hey all - Stripped spark plug threads in the head, looking for advice, thanks in advance.

Background - I have an '03 RAM 1500 with the minivan engine (3.7L V6), 150k miles. Noticed a knocking sound, pulled the code, misfire on cylinder 6 (rear passenger side). Found stripped spark plug threads in the head on cylinder 6. Spark plug was completely loose and had been getting shot into the coil pack. One deepest thread is still intact (I could thread an adapter for a compression checker into them) but the threads on the spark plug don't reach that deep. Assuming a previous owner had over-torqued the plug in the aluminum head, who knows.

Here's the question - Anyone have experience with this repair? Did you take the head off or were you able to helicoil it in situ? If in situ, which helicoil kit did you use that offered sufficient length to get down to the spark plug threads and also allowed clearance to work in the limited space? Any other tips (things to remove for better access, how to keep the hole square, don't even try it without removing the head LOL, etc). Keep in mind this is the back cylinder and has limited access.

Thanks all

 

[djh3]

Unfortunately yes I have experienced this. On 2 different motors a 4.7 dodge and a 2.0 I think it was Neon. So the Neon litterly blew the plug out of the head. The 4.7 was galled when I pulled the plug out and basically pulled threads out with it. So what I did was run that cylinder to it's TDC to minimize space under it. Bought the thread insert kit. You will have to drill out the head some, then tap to put the helicoil/repair thread in. So while I performed this I tapered down my shop vac to about 1" hose so I could get close to plug hole. Turned on while I did drill and rethreading, hoping to suck majority of filings into vac. When done got hose into plug hole and sucked out filings. Then I shot a pretty good dose of WD into cylinder. With all the plugs out I rolled the engine over a few times. I may have shot compressed air in it first I think. Installed plugs and drove into sunset. The Neon my son traded about 3-6 months later never another problem. The 4.7 was in the wifes Durango and it happened @ about 90 k. I just sold it and it had 206k on it with no problems.

 

[ski_shop_cam]

Thanks djh3. Yeah that’s the basic plan I’ve had in mind. Need to take a few measurements tomorrow and see what I can find for various helicoil kits. Not much room above this cylinder so will probably have to find a right angle drill too. I’ll check back in with a few photos.

 

[69 XS29L]

HeliCoil uses red Loctite which will soften due to heat. I seem to remember some kind of small lock/friction point on a spark plug insert. You may be able to simply be able to tap it out again. If it is as loose as it seems, this might not be your option.
I cross threaded and broke off a plug in K-Car head many years ago. Ran the cylinder around past combustion to BDC I suppose, then just a bit up to make sure the exhaust valve was open. Set the shop vac to 'blow', stuck it in the tailpipe. Constant pressure to the cylinder blew all the fragments out as I drilled the plug base and retapped the plug hole.
Good luck.

 

[ski_shop_cam]

Interesting thought on the positive pressure, I like it. I ordered the Lisle 65200 kit off of Amazon, delivers tomorrow. Should save me from having to use a drill, even a small right angle drill has a tough time fitting square over this cylinder. Have some time-cert 500F thread locker to put on the insert threads, but the inserts have a knurled portion and they get swaged in. I'll check back with any tips once it's done (assuming we get there!)

 

[69 XS29L]

That looks like the setup for sure, solid. I don't remember anything that nice or specialized. The only plug my dumbass ever broke off in a head some other mechanic cross threaded, and I just got impatient getting it out. A hot engine, wobble socket adapter on an easy triggered impact would have avoided the mess. This happened back in '88 or so. Reliants had an inline 4cyl., plugs all facing front, easy to get to.

 

[djh3]

Correct on the red thread locker. But I think the kit comes with a "special" locker. Green would probably work. But it sounds like your on your way. Good luck.

 

[ski_shop_cam]

Yeah the lisle kit does not include thread locker. They also recommend a thread chaser which is not included, but they sell separately.

Any idea how to know if I’m at BDC between intake/compression or power/exhaust without taking the valve cover off?

 

[69 XS29L]

If locker is not included, then my guess is it's not needed, no worries. Can't go wrong with Lisle, OTC, MAC or MATCO special tools, they all look the same to me. Usually very well made in the U.S., they know their business.
Sure, compression/power strokes are easy to find, air is pushing out of the spark plug hole. 180 crank degrees in engine rotation direction after that is bottom, the exhaust valve should be open. If you don't already know, there's a couple ways to figure rotation direction, bump the starter is the easiest. A thin wood dowel or long skinny screwdriver inserted in the plug hole to rest on the piston should help you visualize it. Turn slowly by HAND, the dowel will follow the piston top.

 

[djh3]

Yes I use a coat hanger or welding rod.aluminium rod something like that.

 

[ski_shop_cam]

Ok checking back in on this one. The Lisle kit is is a pretty good setup. It uses threaded inserts and comes with four different lengths, including three in the 11/16" length which is what the '03 1500 would need (finish reading this before thinking that's the final answer!). Unfortunately, the three 11/16" inserts were manufactured incorrectly and had most of the threads on the inside bored out. I ordered some from O'Reilly and picked them up the next day, only stocked at the dist center.

In the back cylinder there is clearance to get all the tools in and out. You don't need a drill at any point, only ratchet and extension. I didn't have any existing M14 threads in the head so I had to apply quite a bit of pressure to get the tool to bite and cut initially. Once the larger threads on the tap started cutting it helped.

I used grease on the tap and would pull it out about every 1.5-2 full rotations to clean the chips off and put new grease on. Keep in mind you're cutting the significantly larger and cutting threads all at once, not just tapping a hole.

All was good UNTIL about 8.5 full turns in and then STOP. Tap did not want to keep cutting. After a bunch of in between steps, our best guess is that the larger diameter of the tap eventually interferes with the exhaust valve seat. Maybe you could power through this, we did not. Instead we used a shorter insert (7/16", which we took an additional 0.040" off of). The cleaning process was a combination of compressed air, shop vac with a straw taped to the crevice attachment (taped perpendicular to the hose, making it look like a fang, helps to get the straw in the back cylinder because you can't come straight in with the hose), and some blue shop towels taped around the end of a screwdriver (like a long q-tip) dunked in solvent to clean out grease at the washer surface and clean the threads before installing the insert.

We threaded the insert in with the time-sert 500F thread locker, and waited about an hour. Don't use too much or it'll be pushed out of the threads upward and try to glue the insert installer tool to the insert as well. Then we pulled the insert installer tool out (leaving the insert in), and then swaged it in place. NOTE: Make sure the insert is fully threaded into the head and that you have deep enough threads, you don't want the knurled section of the insert sticking up above the washer face. The swaging is somewhat difficult because you don't have swing room. We used a 4lb sledge with about 1" of swing, definitely swaged it some, TBD if it was enough.

Currently the truck is on the battery charger, hope to fire it soon.

 

[14vern]

🐏 👀

 

[djh3]

Mother is necessity of invention friend. Sounds like you got er licked. I had not thought about the valve arrangement on the Hemi vs the 4.7

 

[ski_shop_cam]

Or the real big boy - the 3.7!