Spark Plug Hole?

[brewsy]

Hi All,
Trying to do my research for my long term project so hoping that one/some of you may be able to offer some advice?

Stock VW spark plugs appear to be 14mm in size and on the heads I want to use, 1300DP, they are notorious for cracking between the plug hole and valve seat.
What I'm looking for is a method to reliably fill and then redrill the hole but probably at 10mm therefore leaving more 'meat'.

Any ideas?

Cheers,
Marc

[samotorsport]

Never tried it myself but had the same idea in mind, couple days ago I TIG welded a broken cooling rip at a cylinderhead and it worked pretty well.
Preheated it to 100 celsius in an oven and welded it with standard AL 99.5 filler rods.
Guess there are better ones around
Might be an idea on how to weld close the holes before redrilling them.

[leec]

It may be worth speaking to Lee Maynard (Lee's Heads) or GAC VW . Both specialise in VW cylinder heads.

[mikko k]

Al 99.5 rod is too soft. You have to use AlMg5 rod.

After welding you should replace valve seats. They will get too much heat.

[samotorsport]

In my case it was only a little corner at a cooling fin , but fir the spark plug hole i agree , different rod and seats to be checked redone.
Guess when this kind of work a complete headjob is the best way to go anyhow


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[brewsy]

Thanks Gents,
Interestingly I saw a video the other day from Papadakis racing in the states where he plugged the direct injection ports on the new Supra/BMW 6 cyl engine.
They made an ally plug that was an interference fit, nitrogen cooled it and then inserted into the head.

Therefore I was thinking that if that would work on a 1000BHP high pressure turbo engine then it should probably work in this application.

Now to find somebody in the UK that can do it...  

[samotorsport]

I am not to sure about this , i guess they plugged the hole for a different reason
In your case the original materiel would still be thin and tend to crack . Maybe even quicker due to the fact it is put under stress even more due to the tight fit of the plug.
I guess the only way you can have more real material to prevent crackd is to add some by welding it in.



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[brewsy]

I guess the only way you can have more real material to prevent crackd is to add some by welding it in.

Hmm,
Fair point and perhaps only one way to find out!

Papadakis did it because they didnt need/want DI on that motor and just disconnected the fuel and electrical supply to the injectors but it turned out that they were designed to be cooled by the fuel going through them and overheated and 'blew out' allowing burning charge directly out of the top of the cylinders!

Cheers

[Martin S.]

How about threaded inserts? No welding required. I wonder if anyone makes an insert that would let you drill/tap the stock hole and allow a modern 12 mm plug to be used.