Greetings: Changed the plugs on my2005 8 today. I thought it went too easily. My torque wrench is older than I am and just about works. So I tightened the plugs firmly but did not gorilla them. The car ran great no more shudder at idle . Now I read that overtightening can cause the plug to reach the Apex seals and tear them. Did I just screw up big time ??? Any info would be appreciated.
I[m old an senile.
OldDude

 

What did you set your Wrench at? It should be 114 inch lbs if my memory serves me correct but don't quote me. They are very easy to break (I know first hand expierence) but it should be fine as long as you didn't tighten them super hard and hopefully you put anti seize on them so they come out later.

 

Do NOT torque them to 114 ft-lbs. Mazda specs 114 to 156 in-lbs. This equates to 9.5 to 13 ft-lbs.

I've never heard that overtorquing can cause apex seal damage, but I guess it's possible. If you didn't "gorilla" them, it is probably fine.

 

My bad I forgot to put the Inches infront of my 114 it has been fixed.

 

I didnt even use my tq wrench on my plugs, cuz I mean 10 ft lbs of tq ? I can feel it with my hands, my rule is that just tighten it with hand, use some wrench to tighten it a bit more, turn it for another 1/2 circle then I stop.

I've changed my spark plugs 3 times, no problem.

Some piston guys overtighten their plugs, when they start the car it seems to be fine, but as soon as they push it, the piston actually *hit* the spark plugs tip and the whole motor was trashed

So as long as u didnt go *crazy* on it, u'll be fine

 

Greetings: I feel a little better based on the information you have given. I did put anti-seize on the threads and Dielectric grease on the cap. Not worried about breakage just over reaching.
I'm old and senile.
OldDude.

 

Your plugs have a washer on them. You can't tighten them far enough for them to contact an apex seal. I actually remove the washers on my plugs (RX-7). This gets the electrode right up next to the seals. If I'm not hitting them, neither are you.

Keep in mind if anyone installs their plugs the way I do and has a bad experience with it, it's not my fault! I have a 13B housing lying around that I can screw plugs into to see how far they go. I can't vouch for the Renesis housings although they SHOULD be the same.

 

Thanks RG. I feel better about it after all the input. The plug change made quite an improvement in idle quality. Two of the four plugs were carbon encrusted and had oil deposits on the threads after only 8700 miles. Looks like I need to redline it more often and not drive like an old man. Wait a minute, I am an old man.
Thanks again. OldDude.

 

OldDude, you need to drive it like and old man who likes to redline a lot.

 

Are both leading and trailing plug holes identical? Did you mic them by any chance? Since it's a machined seat, there's always the possibility of one being slighlty deeper than the other. Just curious, rg...

 

Greetings: Thanks you all for the help and concern. If RotaryGod and Charles R Hill
both think it is most likely OK, then it's good enough for me.
Now if I can only remember where I left my teeth.
Thanks again.
OldDude

 

The trailing plugs are sitting inside the housing with only about 4 mm opening drilled into the combustion chamber. The plug itself won't come near the rotor even if you wanted it to. The worst case, you'll bent the electrodes on the plug as it presses against the rotor housings external wall. Even if you do get longer plugs, you won't do any damage to the apexes on that one.

 

Trailing plug hole is 2mm more shallow than the leading.
Putting a 21mm plug in that position will distort the housing around the hole and will damage the seals.
That is why folks shim FD plugs in the trailing position.