[VooDoo]

Well.. I need to do aluminum buildup (weld some holes shut, then drill and tap - sparkplug holes)

BUT what is the best material? Besides copper, dont have copper.. BUT bronze? Brass? Stainless? Mild steel? It will have 28mm wide and 100mm long "axle" in the sparkplug hole, so there is "some" mass to it. ANd it will be welded from the combustion chamber side.

[79jasper]

Just a quick question, sparkplug hole on what?
If it's a ford triton engine, it's so common that they make a helicoil specifically for that.

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[VooDoo]

Lotus omega cyl head. SOmeone allready did use the helicoils.. And they are gone too. SO the hole is **ked up.

ANd there is some cracks in the combcustion chamber, so welding will be needed.

[79jasper]

Ah, never mind.
All I can say, is your filler will need to be able to stand up to the constant expansion and retraction from the heat cycles.
But that's about as much help as I can give.

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[VooDoo]

4047 filler.. Done gooooood in past. No problems ever.


I think the brass or stainless would be way to go? bronze may couse problems... zinc boiling?

[Braehill]

VooDoo,
Given your choices, I'd would go with the Stainless.

Len

[Superiorwelding]

I also agree with the SS. One warning however, even though you are on a/c you can still melt or "weld" the SS so I would use as thick and big a piece as possible. Jody had a video using a thick piece of SS as a backer for alum.
Copper or brass will work as well.
-Jonathan

[Arno]

Perhaps bit left-field. but would/could a carbon/graphite rod work as well?

Might be agood idea to fit Time-Sert inserts as a final fix too. They are more robust than helicols and should give a much longer service life. ( http://www.wurth.co.uk/hand-tools/threa ... ric-coarse )

Having said that.. With such a rare cylinder head it may be useful to get a machinist involved and perhaps see if it's an option to grind out all the damage/cracks and then completely fill and re-machine the sparkplug holes?

Probably will need to bolt the head down on some form of base plate and (pre)heat and cool it gently to stop it warping.

Bye, Arno.

[zank]

I personally use bronze heat sinks for steel and titanium. You want to pull the heat away. Stainless does not conduct heat as efficiently as bronze or copper. The higher heat conductivity also makes it less likely that you will actually puddle the heat sink itself. Just my $0.02.

[TRACKRANGER]

I know you mentioned you don't have copper, but if this is an expensive component and failure is not an option, then it might be worth investing in copper to help you do the job.

Good preparation often takes more time than the job itself. Selecting and incorporating the appropriate backing material is all just part of the proper preparation process. Stainless may work, but don't expect it to pull the heat away from your weld region.

[rick9345]

4 parts to brazing with Graphite

http://turnwrightmachineworks.com/2014/ ... ng-part-1/

I belive Braze wets at higher temp than Alum

could call him to ask about TIG

[Rick_H]

I also use a piece of bronze 95% of the time, works great.

[VooDoo]

Well.. we did make a copper backing and worked great.

BUT there is a another broblem.. Its pretty rare cylinderhead that im working on and its CRACK SENSITIVE.. tried to weld some more after part was ~only 100c temp.. Crakked after welding. It was like "stopping the weld.. ping-ping-crack" Like strait away.


SO.. IT needs heat to be welded.. but how much can i preheat cast alum?

[Rick_H]

I would pre and post heat to 350°F....them wrap it up in a blanket and let it cool very slow....

[VooDoo]

How long postheat? hour?

[steeldr.]

any metal will work if you don't direct the arc on the backup material. The molten aluminum will not bond to any metal , its not hot enough. Weld one side ,then turn over and check for non fusion ( grind out with a carbide burr) then weld the other side and prep for drilling or milling.
I have welded several motorcycle heads using this process,and using 4043 al. filler wire with good results........Ron