Changing Spark Plugs, Cross Threaded Plug Port

[4drftn]

changed my spark plugs today in my R33 gts-t (rb25) and all went well but doing the last one i discovered while getting plug out it was tight all the way out, put the new one in and it looked to be slightly off center and.

it has been previously cross threaded and has made it quite difficult and now a problem.

put it in straight, car seems to run fine with a very slight miss, and idles high (but idled high before doing it) but unsure if its from this because it was missing like mad before i changed them

now my biggest worry is losing compression, because the thread is stuffed it seemed to have not gone in as tight as it should tightening 1/2 - 2/3 of the way, but didnt keep trying to tighten it to much more as i didnt want to completely strip the thread, and push the metal down into the head

has anyone else had this problem? whats the best way to fix it? does the head have to come off? i was advised to use a heli coil, any alternatives, suggestions or comments.

cheers 4drftn

Edited March 21, 2008 by 4drftn

[adam-__-]

That doesn't sound too good. At one stage I thought I cross threaded the oil filter, but luckily it was just the wrong size filter.

Good luck with it though mate. Hope it isn't too expensive to fix up.

[sneezy32gt4]

If It were me, id definatly take the head off befor trying to re-thread it as metal filings etc will drop straight into the cylinder... its not to much of a c**t to take the heads off, just make sure you get all the torque settings for head bolts etc.

and if your not used to doing much mechanical work, try and do the job in one day, that way there's less likely chance of you forgetting something.

Good luck with it dude, id probally be in tears :S

[Proximity Motorsport]

well other than helicoils if you dont want to rip it off and you start to be loosing compression through the thread, try out some thread sealants. Loctite make a liquid thread tape.... not sure what temps it can handle but i used it in my plenum etc.. I think its in the 500 series of loctites, might be worth checking out. Personally though id go get advice from a mech

[tridentt150v]

Forget helicoils and all that other stuff, the only real permanent fix is a time sert. Costs around $100 for the kit, agents were in Newcastle, but you could get them at other places as well.

Use a drinking straw in the cylinder and turn the motor over by hand until you feel TDC. This position will trap any grease and scwarf at the top . Tap and insert/install the time sert, cold roll it etc. Take out your household vacuum cleaner and attach a small clear hose into the nozzle end [use tape] then feed it into the cylinder through the sparkplug hole and suck out any metal shavings that could have dropped in there, twist the hose about and cover as much of the piston top as you can.

Job done, and if done right, you'll have no problems at all.

If someone has a down bore arthroscope, borrow it and check!

[4drftn]

went onto a website for the time-serts and rang a few places about getting one installed but they all never heard of them, they all just tried to explain to me that the helicoil will do the job.

[Jmaac]

Helicoil it, its stronger than the original thread

[4drftn]

yeah i was thinking it will be stronger, the helicoil would be metal and the original thread would be alloy which is soft...

[QWK32]

nah, not really stronger. the helicoil is still pulling up against the alloy.

[Proximity Motorsport]

^^ yeah but if the helicoil is installed correctly with the super tight heat resist loctite etc.. it will make it stroger than the original thread, however if not done properly helicoils can lead to a great big f**kup

[4drftn]

whats the worst that can happen if installed incorrectly?

[4drftn]

well i got it done, he installed a spark plug adaptor, he said it would be a better alternative to installing a helicoil, only had to take the coilpack and plug out, didnt have to take the coil pack cradle.

took him about an hour.