Which helicoil size for r53 cooper spark thread retap?

[ReaderScars]

Spark plug no.1 wants to be elsewhere. The threads on the plug are fine but the head threads are gone.

As per this vid at about 26sec, I want to retap and insert a helicoil:

https://www.youtube.com/watch?v=UPPM5yH9Kik

Possibly by using one of these kits:

http://www.ebay.co.uk/itm/Spark-Plug-Thread-Repair...

Can anyone tell me what size I require?

[E-bmw]

I take it you do realise you need to remove the head to do that?

Otherwise you WILL end up with loads of metal swarf in the combustion chamber.

In answer to your question they are either M14 or M18, and I think both are x 1.25 pitch, but not 100& sure on the pitch for M18.

There are also solid threaded inserts that may be better for spark plus from a sealing viewpoint.

http://www.engineering-supplies.com/product/13987/...

This is just one type, there are many, I am sure someone else will be along with more pertinent experience soon.

[ReaderScars]

Thanks, but there are plenty of people who have done this - or had this done - with the head in place due to the precautions you can take to reduce dropping swarf (lots of grease on the tap, regular extraction and cleaning/new grease), as well as McGuyvering some narrow flexible tube to a hoover to clean the chamber out afterwards.

However I appreciate your warning as well as the link.

[E-bmw]

OK, you sound like an anecdotally guided expert so crack on!

You clearly don't need our advice!

Edited by E-bmw on Tuesday 19th January 18:17

[ReaderScars]

Well, once I get a straight answer to 'what size helicoil do I need?' I might be on the way

[Megaflow]

Measure the spark plug.

[Mr2Mike]

ReaderScars said:

Well, once I get a straight answer to 'what size helicoil do I need?' I might be on the way

You could just measure the spark plug that fell out of head. If you don't like to get off your chair too much then use the web to find out what NGK plug code is required for the year/model and use the NGK spark plug decoder to determine thread diameter and length.

Edited by Mr2Mike on Wednesday 20th January 22:14

[E-bmw]

^^^^ Wot they said.

In other words why should we be bothered to google what you can't be bothered to?

[ReaderScars]

E-bmw said:

...why should we be bothered to google what you can't be bothered to?

You don't need to, you're a genuine expert rather than an internet one like me.

[ReaderScars]

Megaflow, MR2Mike - I get the new threaded insert has to be the right/matching pitch to the plug, but can I just retap or do I have to drill out?

Additionally this US site, Pelican Parts show a load of different sizes for the insert:

http://www.pelicanparts.com/cgi-bin/ksearch/pel_se...

I was kind of hoping someone, having done this job in this model, would see the thread title and respond.

[thebraketester]

If you've never drilled and tapped before I suggest either letting someone else do it who has, or doing a fair amount of practice before hand.

[Megaflow]

ReaderScars said:

Megaflow, MR2Mike - I get the new threaded insert has to be the right/matching pitch to the plug, but can I just retap or do I have to drill out?

Additionally this US site, Pelican Parts show a load of different sizes for the insert:

http://www.pelicanparts.com/cgi-bin/ksearch/pel_se...

I was kind of hoping someone, having done this job in this model, would see the thread title and respond.

Generally, very generally, the pilot drill for the helicoil tap is just bigger than the OD of the original thread. You are supposed to drill out first, but I have fitted helicoils by tapping the original hole before when space is an issue to get the drill in.

[Mr2Mike]

Megaflow said:

Generally, very generally, the pilot drill for the helicoil tap is just bigger than the OD of the original thread. You are supposed to drill out first, but I have fitted helicoils by tapping the original hole before when space is an issue to get the drill in.

M14 heliCoil requires a 14.3mm drill prior to tapping. Going straight in with the tap may be possible, but it could get very tight and snapping a tap off in the spark plug hole is guaranteed to spoil your day.

[ReaderScars]

Mr2Mike said:

M14 heliCoil requires a 14.3mm drill prior to tapping. Going straight in with the tap may be possible, but it could get very tight and snapping a tap off in the spark plug hole is guaranteed to spoil your day.

Thanks for the info. Some of the spark plug repair kits I've been looking at have drill bits, some don't, hence the confusion on my part.

However have spoken to a local spannerist who's done a handful of time-serts on minis and it looks like he'll be taking this on.

[PositronicRay]

ReaderScars said:

Mr2Mike said:

M14 heliCoil requires a 14.3mm drill prior to tapping. Going straight in with the tap may be possible, but it could get very tight and snapping a tap off in the spark plug hole is guaranteed to spoil your day.

Thanks for the info. Some of the spark plug repair kits I've been looking at have drill bits, some don't, hence the confusion on my part.

However have spoken to a local spannerist who's done a handful of time-serts on minis and it looks like he'll be taking this on.

That's a sensible option.

[mattyc69]

E-bmw said:

OK, you sound like an anecdotally guided expert so crack on!

You clearly don't need our advice!

Edited by E-bmw on Tuesday 19th January 18:17

What a loser.......