HD cylinder head repair?

4047 is my favorite rod for aluminum castings. It has twice the silicon content of 4043, and gives better wetting, a lower melting point, and less shrinkage. Not the easiest stuff to find. Call around your local stores. There is usualy somebody with a box of it in the backroom.

As Ernie stated-4047 is a very good alloy, but hard to find.

4043 is a resonable alternative, however, as is 4145.

4043 should be available at any weld supply shop.

As a loose rule, most aluminum castings are a silicon based alloy. The silicon amounts will vary. 4043 is a 5% silicon alloy and 4047 is a 12% silicon alloy, if my memory is any good. (Check this-the 1970's were verey good to me!!) Additional silicon can reduce the melting temps somewhat-so pay attention to your base material. In tig-"Smoke the joint"-then add filler.

I have welded literally tons of Harley castings over the years, and have found that 4043 works as well as anything. Never had a problem.

I'd use 4047 or 4145 if I had it though. These alloys are great for appearance, but can be a bit 'runny' at certain times, due to their lower melting temps.Match your alloy to your requirements.

Do keep in mind that there are 5000 series castings out there-but they are rare.

It is important to keep in mind that we don't want to use 5000 series wire(magnesium alloyed) on a silicon based casting.There are definite metallurgical considerations here. A culprit known as mag-silicide, a great underbead cracker is easily produced.

Any 4000 alloy will give good welds on silicon based castings. The higher the silicon content, the better the "wetting" of the weld bead.

These 4000 series alloys will respond to heat treatment if desired, but they will give adverse results if anodizing or alumilite is being considered. The extra silicon can sometimes cause some cracking issues with relation to weld dilution.

Aluminum is not hard to weld, only different.

Keeping the repair to original dimensions can be important. If this is the case-heat the outer perimeter first. This will expand the casting, putting your welds in compression upon cooling, greatly reducing cracking and keeping dimensions closer. Try to keep a limit of 350-400 degreesF, so as not to upset any heat treatment the particular weldment may have had previously.

Hope this helps. any questions-email directly.

Good Luck

brad

There is a spool of 4047 on Ebay at the moment. Didn't know if you are looking for tig filler rods or spool. I suppose you could use the spool as filler rod too. You certainly would have a lot of it.

Good luck. Randy

Here is the auction