Spit a plug, What to do?

2007 Tahoe Just under 200,000 miles

Short story, my engine spit the cylinder 4 plug. I installed a "heli-coil", "spark plug intert", "cert"... however you want to refer to it, a week or so after it happened. Something I had never done before and had my concerns but went through with it anyway. It lasted a few months then it happened again. I'm certain I did not install it properly and it spit the same plug with "cert" once again. I parked the truck and it's been sitting since wasting away. I've debated replacing the head but doubt my mechanical ability, selling it as a whole or parting it out. I've researched replacing the head and honestly I'm a bit intimidated. I hate to get rid of it, hence why it's been sitting for so long.
Anyway, I'm hoping for some advice. I'm not a mechanic but do almost all my own repairs/maintenance. I have a mechanic buddy that I have worked on my vehicles with in the past when things felt like they were beyond my scope but I've moved quite a bit of distance from him and doubt he would be available to help on this one.

Thanx in advance for any input.
J

Pull the head. In fact pull both heads, drop them off at a machine shop to have them gone through. They will be able to tell you if the one head is salvageable. If not, they can set you up with a used head that they have gone through.

Considering the miles on it, wouldn't hurt to put new lifters in while you have it apart.

What causes this to happen?

Over-tightened plug? Overheat softening the aluminum?
Seems like interference should just smash the tip..
Detonation should crack pistons first..

Heads on LS engines are incredibly easy to replace, just takes some grunt to torque them back on. Time consuming, yes. But not technically challenging. No expensive or specialized tools required either. You can probably do both in 8-10 hours total to remove and replace.

Do as @rdezs mentioned. Or call your local machine shop, or ask them to see if they have any heads already machined and ready to install. There should be an abundant supply of this generation of Gen IV heads around.

@mikez71 This is the first time I've head one of these engines spitting out a spark plug. No common at all. I think some engines like the Ford Triton 5.4 had marginal spark plug engagement on the casting. Basically a design flaw (and maybe combination or low or high factory torque specs? can't remember). Not the case on the GM engines.

S4NM4N said:

2007 Tahoe Just under 200,000 miles

Short story, my engine spit the cylinder 4 plug. I installed a "heli-coil", "spark plug intert", "cert"... however you want to refer to it, a week or so after it happened. Something I had never done before and had my concerns but went through with it anyway. It lasted a few months then it happened again. I'm certain I did not install it properly and it spit the same plug with "cert" once again. I parked the truck and it's been sitting since wasting away. I've debated replacing the head but doubt my mechanical ability, selling it as a whole or parting it out. I've researched replacing the head and honestly I'm a bit intimidated. I hate to get rid of it, hence why it's been sitting for so long.
Anyway, I'm hoping for some advice. I'm not a mechanic but do almost all my own repairs/maintenance. I have a mechanic buddy that I have worked on my vehicles with in the past when things felt like they were beyond my scope but I've moved quite a bit of distance from him and doubt he would be available to help on this one.

Thanx in advance for any input.
J

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I don't see how a split plug would require anything other than a new plug.
might not be any fun getting the broken one out but unless you damaged something doing so, i don't understand the need for a helicoil.

I did strip one out decades ago and that required a fix.

If I read the OP's description properly, sounds like it already had a helicoil and it blew out. A second one is probably not an option.

Why would it blow out on an LS head? Spark plug torqued down to the point where it's almost stripped, effectively weakening and damaging the threads.

strutaeng said:

This is the first time I've head one of these engines spitting out a spark plug. No common at all. I think some engines like the Ford Triton 5.4 had marginal spark plug engagement on the casting. Basically a design flaw (and maybe combination or low or high factory torque specs? can't remember). Not the case on the GM engines.

Click to expand...

Yeah I had a blown 5.4 Expedition back in the day, Ford used like 3 threads to hold the plugs in. Those motors already liked to spit plugs before adding boost…but helicoils and/or time certs were pretty durable, permanent solutions that Ford themselves recommended as the fix.

Or not tightened enough.

Doubeleive said:

I don't see how a split plug would require anything other than a new plug.
might not be any fun getting the broken one out but unless you damaged something doing so, i don't understand the need for a helicoil.

I did strip one out decades ago and that required a fix.

Click to expand...

Spit not split. The plug threads were ruined so i put helicoil/cert in place but did it wrong I guess and it spit the plug again with the cert attached to the plug.

rdezs said:

If I read the OP's description properly, sounds like it already had a helicoil and it blew out. A second one is probably not an option.

Why would it blow out on an LS head? Spark plug torqued down to the point where it's almost stripped, effectively weakening and damaging the threads.

Click to expand...

Can't say why it happened the 1st time. The plugs were in quite a while, honestly past needing to be replaced. 2nd time I'm guessing was my fault by not doing install properly. I was very careful and used a scope to look into cylinder but must have done something wrong?

S4NM4N said:

Spit not split. The plug threads were ruined so i put helicoil/cert in place but did it wrong I guess and it spit the plug again with the cert attached to the plug.

Click to expand...

still doesn't make sense, what is a "spit" spark plug, you must mean "stripped" ?

Doubeleive said:

still doesn't make sense, what is a "spit" spark plug, you must mean "stripped" ?

Click to expand...

I think he's saying the spark plug was basically "ejected" from the threads? Stripped in the process? I'm just guessing here...?

S4NM4N said:

Can't say why it happened the 1st time. The plugs were in quite a while, honestly past needing to be replaced. 2nd time I'm guessing was my fault by not doing install properly. I was very careful and used a scope to look into cylinder but must have done something wrong?

Click to expand...

J - Plugs were probably over-torqued, or the threads seized to the aluminum threads in the head, shearing them off when taken out.
Did you use a dab of anti-seize on the plug threads before installing? I always do and have never had stripped threads, nor had any plugs come loose.

If you've done other work, replacing the heads is not beyond your capabilities... is just kinda scary the first time you do it. Watch some Youtube videos and you'll see it's not too bad. Getting a rebuilt set of heads from your local machine shop or cylinder head exchange is a great option. They'll take your old heads as cores. Good opportunity to install new head, valve cover and intake gaskets and get her sealed-up and leak free.

FWIW just did my first helicoil 2-weeks ago at age 67. Have wrenched on cars since I was 14 and never needed one until now. We had bought our '13 Tahoe used and the PO took it to dealer/shops for service. Had leaky valve cover gasket which should have been easy... found out why it was leaking. Whoever changed the valve cover gaskets before had massively overtightened all the hold-down bolts. Should only have been 99-108 inch/lbs. Thought I was lucky as all the hold down bolts seemed to come out fine except for rearmost on driver's side which wasn't anywhere near as tight as the others. Cleaned up everything, installed the new gaskets bolt seals and proceeded to torque them down with a small 1/4" ratchet and 8mm socket. Snugged the front three and when I got to the rearmost bolt, it initially started to grab but it gave way and just spun... stripped. Removed the bolt and the aluminum threads were still wrapped around it.

A $40 6-1.0 metric Helicoil tap, $40 insert key and $10 drill bit all to install the $1.89 helicoil insert. Also had to buy a right angle drill adapter at Harbor Freight ($20) so I could drill-out the damaged threads before re-tap and install the helicoil insert. Pretty straightforward and saved having to pull the head!

Wishing you best of luck as you proceed w/swapping out those heads!
Kevin

The inserts to repair the heads are not all the same, aluminum heads have more threads than cast iron heads but both use a 14 mm insert or heli coil

If you used the shorter cast iron insert it would explain why the plug & insert blew out, the softer aluminum needs all of those threads to hold

If that's the case, I would get the correct insert kit, re-tap the hole & install a new plug with the new insert and a liberal amount of green loctite on the insert. Tighten it well & let it sit overnight

You will likely never get that plug out again if you do this because a liberal coat of loctite will creep between the plug & insert a little; so buy a good quality plug but that green loctite is designed for extreme heat & permanent bonding so it might do the trick to get you the last 100k out of that LS

You have nothing to lose at this point, just be careful to do this insert correctly & that you have a long enough insert to use all of the threads in the plug hole

Good luck!

As stated above, never seen or heard of a plug spitting and or splitting on a LS! Sounds like plug hole is stripped and if it can't be repaired then pull heads.what heads are on it?

There are various mfgs of inserts, so it is worth a look for a slightly larger dia to try again. Measure what you now have as a start.
Do NOT use heli-coil type, only full insert.

Timesert. https://www.timesert.com/