piston hitting spark plugs

[dilldb]

Hi I just changed the spark plugs and they were bent at the tips so I reinstalled some NGK ones that I got at canadian tire. They're gapped right but a week after I installed then I checked one and it was a little bent. I'm not sure what exactly would be causing this. I'm hoping it's just tons of carbon build up. What do you guys think? The truck still runs but not that great since it skipped a tooth on the timing.

The tuck is a 84 nissan 720 2.4l 4x4 king cab... Any help would great.

[lctmjw]

Wow, if you're piston-whacking the plugs, you almost definitely have the incorrect ones. If you're sure that you have the right plugs, look for signs of detonation/pre-detonation. Prolonged detonation causes enormous stress on lots of things, including plugs, and could easily cause bent electrodes. Notice any knocking/pinging? You say that you're a tooth off timing-wise, I'd work to rectify that before all else. Having jumped time won't precipitate the piston striking the spark plug(s), but could cause detonation if the timing is advanced by skipping a tooth, though I would think if you "jumped" time it would be slightly retarded, not advanced. My Z24 is an 8 plug engine, I assume yours is the same?

[dilldb]

Yeah mine is also 8 plugs... later today I'll go check exactly what plugs they are. When I pulled the plugs out the tips were brown and the end of the threads were black. The engine also backfires out the intake.
Also I think the plugs tips bending are progressive. I don't think they bend in the first ignition but after a few hundred. I wont be driving the truck till I can fix these problems I'll be changing the timing chain and gears asap. One more thing is one of the last owners of this truck changed the timing chain with a used one and when I got it the timing on the distributor was adjusted all the way to one side. When I tried adjusting it it would run rough so I'm thinking that the timing could of been out a tooth since the last owner changed it and didn't bother to fix it properly. Anyways thanks for the reply it really helps ^^

[lctmjw]

Yeah, it totally sucks following the "work" on a vehicle performed by someone who doesn't know what they're doing, or doesn't care to do it correctly. Since you added that it's backfiring through the carb, I'll go a little further out on the limb with detonation being the cause of your bent electrodes. Either way, you have timing issues to resolve. Why would the previous owner replace a t chain with another used one?

[dilldb]

I'm not sure exactly... I've heard that he's careless and into bad drugs. I just hope that the piston and walls are in good condition. The truck has about 305 xxx km on it and doesn't burn a drop of oil so it should be good.

[dilldb]

I just installed a new timing kit. The engine runs so much better now. The plugs are not bending anymore... and I looked into it and I do have the wrong plugs(but they were not hitting the piston) I'll be getting new ones soon. The spark plug timing was off by a lot but now it's set to 3 degrees. So everything is almost perfect now ^^ thanks for your help! when I first saw that the spark plugs were bent I almost rolled the truck down a hill xD.

[lctmjw]

Good to hear, glad you're on the right track and it's running better.