TIG Pencil torch?

[Jim Davey]

 

[Jim Davey]

If you preheat tha casting first, you can get the heat into the metal faster so the torch isn't doing all the hard work. However, putting the torch head into a roasting hot tube (which is exactly what a port is) won't help cooling either.
If this is something you have to do then you are more than likely going to have to go water cooled to get the torch to last.

 

[Ed.]

The video link in post 3 says, that those are also available in a water cooled version that does 140A

 

[Jim Davey]

They are, and this can be improved upon by using a cooler with a powerful pump and efficient radiator.

 

[shambo]

Would it be easier for OP to use aluminium bronze or silicon bronze and braze it instead of actually welding it? Or is the melting point going to be too low for it to be regarded as a worthwhile repair?

 

[Jim Davey]

That could work just as well. A cylinder head shouldn't get anywhere near the melting point of either of those materials, in the port at least.

 

[shambo]

Would the head still need to be preheated first?

 

[Jim Davey]

I'd guess so, it's never a great idea to try and weld a pinpoint area of 18"x6" thick ally, without warming it up first.

I'm lucky though, I have a large oven that goes up to 350 degrees.
(Transformer added for scale!)

 

[shambo]

So even if brazing it would still need to be heated. Something to remember. I thought if brazing it the OP could get away without per heat

 

[Jim Davey]

You have to get the material up to temperature before you can get a weld, that's a big ask on something that is as big a heat soak as a cylinder head. So yes, pre-heating is pretty much essential.

 

[Chris Stevens]

if it's to build up the ports, and welding isn't that practical, try searching for the specialists who do porting works and find out what type of resin / epoxies they use. Might give you more options.

weldiong would be more permanent though.

Not a great idea to epoxy exhaust ports, which is what OP wants to weld.

 

[MCKDAVID]

ah, didn't catch that... never noticed it was the exhaust, must learn to read....

 

[hotrodder]

Aluminium bronze or silicon bronze and an aluminium cyl head wouldn't end well... they're both copper alloys with a melting temp around 400°C higher than aluminium
4047 filler wire is about as good as things are gonna get with regards to heat input needed as it's the Eutectic_composition for AlSi alloys and can be used for brazing ally as well welding it

FWIW if the job is a big lump of ally and i can't reach what needs to welded with a wp24w then i pass... gas coverage from a 24 can be fairly pants at times (putting a gas lens on helps but makes 'em bigger/bulkier) and when you're feeding wire through one side of the port (or whatever) with the torch stuffed down from the other end there isn't room to add another argon source and still be able to see what you're trying to weld. With aluminium and watercooled micro torches personally i've always found the gas coverage thing to be more limiting than amperage rating

 

[Chris Stevens]

OP doesnt seem interested in this thread now, so I guess he has been able to find a used head, which seems to me a lot less hassle than trying to weld up a bodged "porting" job?

 

[shambo]

Aluminium bronze or silicon bronze and an aluminium cyl head wouldn't end well... they're both copper alloys with a melting temp around 400°C higher than aluminium

Thanks for the info. I thought it required a lower temperature to braze with those.

 

[gt6s]

If it is not ground through and valve seat undamaged. Leave the exhaust port alone. It will do no harm. Unless of course we are talking two stroke.