1GR-FE plug thread - durability

I just replaced my plugs due to a combination of hard starting (extended crank), intermittent misfire and the fact that I don't know how old the plus were (bought truck used). Replaced with Denso/

$9 Toyota 90919-01235 Toyota Genuine Spark Plug

Toyota 90919-01235. Starts much quicker now.

I always dry torque plugs to spec. Several plugs had a small amount of oil in the coil (plug) hole, tiny leak from from the valve cover, I'm sure. Over 300k miles, I expected a bit. But, of course, I had my 3/8 drive torque wrench set to 15 ft lbs and, on one plug, after the crush gasket felt like it had crushed sufficiently, I didn't feel a click from the wrench. Of course I panicked. This wrench is very reliable, but I was extra cautious with the plugs because the heads are aluminum, and there was a little oil in the plug hole, so it's considered wet torque now. I loosened the plug and retorqued, slightly lower, using a 1/4" drive inch pound torque wrench. Got a nice consistent click this time.

I don't think the retightened crush washer/gasket would be a problem, as I've reused gasketed plugs years ago with no issue, but was wondering if anyone ever had a plug strip out on a 1GR-FE head? From what I've heard, these particular aluminum heads are extremely strong and if plugs are removed and installed with a cold engine, there's little chance of screwing anything up.

By the way, a previous owner or shop had replaced the plugs and snugged two of them to what I'd call 'nut driver' tight. I was able to remove them with almost no effort. Several had uncrushed gaskets, too.

But anyway, just wondered how much abuse these spark plug threads tolerate. I think the reason anyone might have trouble is from trying to remove a high mileage plug (possibly tightened a lot also) from a hot engine. Other than that, they seem quite robust.

 

I don't bother with a torque wrench. I go slow to feel the washer crush, then about 1/2 turn more.

Never blew one out of my 7k RPM Solo II car with aluminum heads, so I'd not fret it in my truck either.

I'd say you've ID'd your biggest risk, that being not knowing how they were treated in the first 300k. But if you found no cross threading and they are all seated well you should be fine.

 

Thanks Bill!

 

Something else occurred to me just now, if I had stripped threads, the plug would have been tight getting back out. It wasn't, felt perfect, and threaded plug back in just fine.
Thanks again for relieving my mind with good common sense advice.

 

I don't like torque wrenches for non critical fasteners, they can help if the person hasn't developed the "feel" for tightening a fastener "if" they know how to use one correctly but I've also seen people damage fasteners by using one improperly all the while thinking they're safe because they have that torque wrench in their hands. I seen them pulled out of a tool box with the previous value still set and witnessed them being used with extensions and even crows feet with no regard to the effect that's having on the leverage. I compared a cheap harbor freight TW to a snap-on and a craftsman digital a few years ago, lets just say I'll pass on letting HF determine if my hardware is torqued correctly.

 

It will be fine.
I used anti-seize an no torque wrench.
I finally broke down and bought a torque wrench capable of going to 15 ft/lbs.

I can tell for a fact, my "feel" was more than 15 ft/lbs.
I bet I was going closer to 20 than 15 with anti seize.

The thread engagement on the 1GR heads is pretty long.
You'll be fine.

You'll likely crack the porcelain and break the plug before you damage the head.
And you'll know pretty quick too. You'll get a misfire shortly at/after startup.

 

Thanks Deogee, you always help me out and I sincerely appreciate your advice! Have a great weekend!

 

I pulled factory plugs out of a 1GRFE with 180k miles on it. These are surprisingly robust engines.