Spark Plug and Helicoil Help Required
Discussion
Chaps
Just wanted to gauge opinion on the below situation from some of the experts on here!
I have recently gone to replace a set of spark plugs on a 'classic' 80's petrol turbo car that Ive owned for a number of years. Its not been used that much but when it has, it's performed well. The previous owner, unbeknownst to me, has replaced all but one of the plugs before, as the one that wasn't replaced turns in the plug hole! So its stripped the threads in the aluminium head no doubt, but rather than using the correct plug with a 16mm Hex diameter, he has used a 19mm Hex diameter plug. Now it turns both ways without coming out that easily, but it is not loose in the hole and requires a little effort to move the plug - i.e. not finger tight. So whilst it is obvious it will loose compression through the plug hole, I'm assuming the 19mm Hex is there to help prevent that and it has simply been bodged to sell it on!
So looking at the NGK website, most 16mm Hex plugs use a 14mm x 1.25 thread and the only 19mm Hex one I can see uses a 14mm x 1.25 thread also. I was thinking that the previous owner may have used a different plug thread to almost 're-tap' the aluminium so that it may seal better, but hopefully this is not the case.
So the ideal solution is to get the plug out and have it helicoiled but I really dont want to get into removing the head (end engine) and my dilemma is it runs at 99% of what it should do anyway.
So I guess my question is, I want to understand what the implications of helicoiling are and what could possibly go wrong with this procedure if done by a professional. Are you always guaranteed it will work if done correctly? Would there be any concerns with what I have mentioned above that are big red lights?
Thanks for the help and sorry for the long post!
Regards
C
Just wanted to gauge opinion on the below situation from some of the experts on here!
I have recently gone to replace a set of spark plugs on a 'classic' 80's petrol turbo car that Ive owned for a number of years. Its not been used that much but when it has, it's performed well. The previous owner, unbeknownst to me, has replaced all but one of the plugs before, as the one that wasn't replaced turns in the plug hole! So its stripped the threads in the aluminium head no doubt, but rather than using the correct plug with a 16mm Hex diameter, he has used a 19mm Hex diameter plug. Now it turns both ways without coming out that easily, but it is not loose in the hole and requires a little effort to move the plug - i.e. not finger tight. So whilst it is obvious it will loose compression through the plug hole, I'm assuming the 19mm Hex is there to help prevent that and it has simply been bodged to sell it on!
So looking at the NGK website, most 16mm Hex plugs use a 14mm x 1.25 thread and the only 19mm Hex one I can see uses a 14mm x 1.25 thread also. I was thinking that the previous owner may have used a different plug thread to almost 're-tap' the aluminium so that it may seal better, but hopefully this is not the case.
So the ideal solution is to get the plug out and have it helicoiled but I really dont want to get into removing the head (end engine) and my dilemma is it runs at 99% of what it should do anyway.
So I guess my question is, I want to understand what the implications of helicoiling are and what could possibly go wrong with this procedure if done by a professional. Are you always guaranteed it will work if done correctly? Would there be any concerns with what I have mentioned above that are big red lights?
Thanks for the help and sorry for the long post!
Regards
C
To do the job properly, the head needs to come off.
That’s said, I did see somebody helicoil a head by filling the cylinder with shaving foam to collect the swarf, then cranking it over with the plugs removed to eject the foam and swarf from the engine. It worked, but I think it should only be used as an I don’t give a toss about this car method.
That’s said, I did see somebody helicoil a head by filling the cylinder with shaving foam to collect the swarf, then cranking it over with the plugs removed to eject the foam and swarf from the engine. It worked, but I think it should only be used as an I don’t give a toss about this car method.
As far as I am aware helicoils were always used in ICE aircraft engines as a matter of course.
I had a cross thread in my Clio 172 cup (Renault themselves did it changing the plugs). I helicoiled all 4 at the same time. THe car went on to circa 200k with no issues. IIRC I was advised to do all 4 as it isn't a great deal of labour and the kit came with 4 plus the tools including the tap.
I had a cross thread in my Clio 172 cup (Renault themselves did it changing the plugs). I helicoiled all 4 at the same time. THe car went on to circa 200k with no issues. IIRC I was advised to do all 4 as it isn't a great deal of labour and the kit came with 4 plus the tools including the tap.
Wouldnt have any concerns on a helicoil done right.
Depending on value etc of the vehicle, you could try DIY in-situ, taking some sort of measures to try and prevent debris getting into the cylinder.
If it was something special and worth a lot of money, removing the head may make more sense. But good chance you could do an alloy head without too much fear of harm in situ.
Depending on value etc of the vehicle, you could try DIY in-situ, taking some sort of measures to try and prevent debris getting into the cylinder.
If it was something special and worth a lot of money, removing the head may make more sense. But good chance you could do an alloy head without too much fear of harm in situ.
stevieturbo said:
Wouldnt have any concerns on a helicoil done right.
Depending on value etc of the vehicle, you could try DIY in-situ, taking some sort of measures to try and prevent debris getting into the cylinder.
If it was something special and worth a lot of money, removing the head may make more sense. But good chance you could do an alloy head without too much fear of harm in situ.
This ^ Depending on value etc of the vehicle, you could try DIY in-situ, taking some sort of measures to try and prevent debris getting into the cylinder.
If it was something special and worth a lot of money, removing the head may make more sense. But good chance you could do an alloy head without too much fear of harm in situ.
apart from I would use a Wurth Time-Sert but only because I have been using them since the 80's Honda only used alloy heads and the cars we see back then sometimes met poor ham-fisted monkey's 
so I am biased towards Time-Serts for their repeatability Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff