Technical Stripped spark plug hole thread...

[Pugglt Auld Jock]

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Expanding taps were patented in 1870

If you don't know they exist, you don't know to look for, ask for them, I guess the back tap became popular with the rise of aluminium heads 1990s

Looking at the prices £5 upwards, Sealy ones are around £15

I've come across expanding reamers and used them, but never thought about an expanding tap. I first saw this type of expanding tap some years ago, which, of course, is intended very specifically to clean plug threads and overcome the swarf problem. However an expanding tap for use in the normal way? Never knew they existed. Every day's a school day as they say.

 

[velvet]

They should go in dry if you are going to torque them up using a torque wrench

Oiled will over tighten them and risks damage

They are coated, no need to oil read link in post 5 should explain everything

Start them by hand they are at an angle



View attachment 476234

although even with an ali head , it can feel dry and stiff..as you say too much is no good

 

[velvet]

They can be re threaded without removing the head.

Looking at that video again, that tap enlarges the hole to allow for the insert so it seems to me that a fair amount of swarf must drop into the cylinder. Does that insert take any make of spark plug ? Is there a standard thread used on all spark plugs ?

 

[Pugglt Auld Jock]

Looking at that video again, that tap enlarges the hole to allow for the insert so it seems to me that a fair amount of swarf must drop into the cylinder. Does that insert take any make of spark plug ? Is there a standard thread used on all spark plugs ?

Nope. Different diameter for different plug sizes and different lengths of insert too. Right kit needs to be bought.

Some swarf in the bores is pretty inevitable. But plenty of grease on the tap and only taking a small "bite" before backing out, cleaning the tap, regreasing and taking another bit helps a lot. Piston at TDC compression stroke before you start and blow out with airline when finished.

On many engines access makes this a variabley difficult job. And don't forget all the plugs may not be aligned identically. For instance the FIRE engines have two plugs with axis leaning slightly to the N/S and two leaning to the O/S.

 

[koalar]

Looking at that video again, that tap enlarges the hole to allow for the insert so it seems to me that a fair amount of swarf must drop into the cylinder.

Already answered

Don't overly worry about the metal swarf

Start the engine with the plug out, blows the majority out

The rest will either pass the exhaust valve or get burnt off

There not big enough or hard enough to cause any damage

The head doesn't burn because it large and soaked the heat away

Small aluminium pieces burn

If you follow the advise in the link I post and you are careful,.the plugs should come out and go back in with any damage, unless they were installed incorrectly in the first place

Three years is nothing

 

[DaveMcT]

A low cost endoscope camera will allow you to look into the cylinder for debris. (Lidl has one right now). Get a rubber tube slim enough to go down the spark plug hole and gaffa tape it to your vacuum cleaner. Check before and after to be sure there's no debris.

 

[velvet]

A low cost endoscope camera will allow you to look into the cylinder for debris. (Lidl has one right now). Get a rubber tube slim enough to go down the spark plug hole and gaffa tape it to your vacuum cleaner. Check before and after to be sure there's no debris.

good idea