Helicoiling of spark plug threads. 1850.

[MIG Wielder]

Is it possible to Helicoil a spark-plug thread with the head still on an 1850 ? I've seen a generic Helicoil tap that does not need a drill and there are 2 You-tube videos that show that this can be done. One by using a high pressure air-line to blow out the swarf and one by using a heavy grease on the tap to catch the swarf and doing it one turn at a time.
What do you reckon please ?
Thanks very much,
Tony.

[new to this]

I think for spark plug holes your better to use time serts ,my brother had one fitted on his Stag while the head was still on the car

Dave

P,S time serts are solid where Helicoils are round wire coils

[cleverusername]

My advice is be very careful. I have ruined a head trying to fit an insert. I didn't have a bench drill and tried to drill it by hand. Slightly off square meant the sparkplug could no longer gas seal in the head.

Even if there is a method that uses a tap, it must involve removing material to make room for the threaded insert. Only proceed if you are certain you can tap/drill the hole absolutely square and straight. If you have any doubts about that, take the head off and use a bench drill or get a machine shop to do it.

[soe8m]

Yes you can. I have a tap specially for inserts. The first part is the original 14mm thread to follow the plug hole and centre, the following step is a roamer and the third is the oversized tap. It's a one piece tool and it's just a matter of screwing into the existing plug hole. It's "plug" size and the hex at the end is also plug size so when there's room for a sparkplug there's room for the tap.

Never use grease when tapping in alloy. Use only thin lubrication like wd40 or similar to have a nice sharp thread in alloy.

Jeroen.

[MIG Wielder]

Hello All,
Thanks for your replies.
I found the combined M14 / Insert centering drill here.
Brilliant product ...
https://www.ebay.co.uk/itm/Time-Sert-44 ... SwwvZZVqLC
... but the cost is quite high and what really defeats it are the import charges

Thanks for the hint on WD40 to get a good thread ! I like the idea of the Time Serts.

Cheers for now,
Tony.

[new to this]

Yes you can. I have a tap specially for inserts. The first part is the original 14mm thread to follow the plug hole and centre, the following step is a roamer and the third is the oversized tap. It's a one piece tool and it's just a matter of screwing into the existing plug hole. It's "plug" size and the hex at the end is also plug size so when there's room for a sparkplug there's room for the tap.

Never use grease when tapping in alloy. Use only thin lubrication like wd40 or similar to have a nice sharp thread in alloy.

Jeroen.

I would put grease on the tap ,that way as you tap the thread the grease well stick to any swarf

Dave

[soe8m]

Yes you can. I have a tap specially for inserts. The first part is the original 14mm thread to follow the plug hole and centre, the following step is a roamer and the third is the oversized tap. It's a one piece tool and it's just a matter of screwing into the existing plug hole. It's "plug" size and the hex at the end is also plug size so when there's room for a sparkplug there's room for the tap.

Never use grease when tapping in alloy. Use only thin lubrication like wd40 or similar to have a nice sharp thread in alloy.

Jeroen.

I would put grease on the tap ,that way as you tap the thread the grease well stick to any swarf

Dave

You can't make a thread with grease on a tap.

Jeroen

[soe8m]

Hello All,
Thanks for your replies.
I found the combined M14 / Insert centering drill here.
Brilliant product ...
https://www.ebay.co.uk/itm/Time-Sert-44 ... SwwvZZVqLC
... but the cost is quite high and what really defeats it are the import charges

Thanks for the hint on WD40 to get a good thread ! I like the idea of the Time Serts.

Cheers for now,
Tony.

Well, mine was around and similar to this.

https://www.amazon.ca/OEMTOOLS-25647-Sp ... B000CMHL1C

https://www.ecstuning.com/b-heli_coil-p ... 33414~hec/

Jeroen