natedogg

Hey, I was just wondering how I could tell if a cross-threaded spark plug would effect my engine.

The guy that owned the car before me did this. I went to change my plugs today and my trailing plug on the front rotor was cross-threaded. It went in fairly smoothly however so I went ahead and capped it with the spark wire, took it for a drive, and it seemed to drive like before.

will a X-threaded plug hurt my engine? It's off center in the hole by maybe half a millimeter when comparing to the other trailing plug. I'm worried that the damage has been done and I will have to pull the engine and replace the front rotor housing all because of some guy's stupidity and inpatience!

jeff_oner

my dad was telling me about his old triumph in which he cross-threaded a sparkplug and while on the road it blew out the hole and messed up some other stuff in the engine bay. he had to have it machined. id imagine that it would be a lot worse on a rotary since the sparkplugs are in the block. anyway you should probably get it machined right away, before you NEED to have it fixed.

natedogg

get what machined? the engine block or the plug?
why couldn't I use a tap and die set on it?

Aaron Cake

iTrader: (1)

If the hole is stripped, leave the plug in it until you can fix it. In order to fix it, the engine must be disassembled to prevent metal shards from entering the rotor chambers. Not a small task.

If it is a trailing plug, you can probably leave it for a few years. If it is leading, it will have to be changed about once a year.

Dave B74

Any competent mechanic should be able to repair the problem with a helicoil. He should be aware of the procedure to make the repair without getting any aluminum in the chamber. A multitude of engines have been done without pulling it out. If it concerns you, have it done. If everything works well now, will it be that bad to wait? I would encourage you to seek out a good mechanic for advice before doing anything. There is no machining to install a helicoil.

Good luck!

Dave

89 GTUs road racer
89 GTU street car
87 Sport road racer in the works

natedogg

I will get a local guy to fix it for me. He has been working on 7s for about years. I hope he does it for free. He owes me anyway because I GAVE him my old steering wheel (the nasty two spoke wheel in my 87).

Anyway, he is going to trade me for my engine for a rebuilt engine with new seals, etc. ! I'm excited about it!