Yes or no too free cylinder heads?

Hi everyone,

I'm a new member, and I have a lot to learn (and indeed equipment to build) before I can play, but… I’ve been offered a dozen or so cylinder heads (aluminium) for free.

Now I’ve read that these are mostly good quality casting aluminium, but some may be mag alloy (and I don’t want to experience a mag alloy fire).

Should I turn the offer down? Is there a way of testing if they contain magnesium? I think they are mostly Ford, Nissan and GM heads, maybe a VW or two? Nothing fancy in there. I understand the best way to go is with virgin alloy, but this seems a good source of aluminium to experiment with if I can get it to an ingot stage in the future.

Also, if I can decide what is safe, would I melt these one head at a time, cast that head into ingots and not mix alloy from another head or doesn’t it matter?

Sorry for the beginners questions.

Thanks,

Ian

 

It depends, hydrocarbon residue and steel hardware in the aluminium can cause problems from the iron dissolving in the aluminium can harm it's properties. A small foundry wouldn't bother with the effort involved and just buy in known ingots but if you're getting up to speed and building a furnace if may be worth having free material to experiment with. Don't forget you are going to have to break the heads up into manageable chunks for the crucible too.

 

Thanks Mark,

I was thinking that I could try to remove studs, knock out valve seats etc and de grease them as much as possible. I know it’s not the same as buying ingots, but it’s free and gives me something to play with while I learn a little.

Cutting them up could be an issue. My bandsaw isn’t big enough to do these. I may be able to get access to a large one at my friends place of work? It’s worth asking.

 

You can try putting some saw cuts in the cylinder heads then get them off the ground with a piece of wood and smack them with a sledgehammer to break them, I haven't tried cylinder heads but it works fine for big ingots.

 

Ian, I would suggest "go for it". They may contain a small percentage of magnesium but generally this would be no more than a "trace" in this particular application. Many, many years ago we made thousands of beautiful and mechanically sound castings from a continuing supply of automotive pistons. The spec at the time was "Y alloy". We melted the whole piston assembly including rings and pins and transferred the aluminium from the melting furnace at just over the melting point to the casting furnace. This avoided any iron, and copper contamination from the mix. I recommend that you do something similar, maybe even dropping it into ingot moulds for re-melt later. There will be all manner of potentially ferrous contaminants in a cylinder head too. Be aware that there will be a healthy (or unhealthy) amount of smoke generated when you brew up!

There are incredibly tight quality controls maintained in the manufacture of automotive components so you can be sure that the base quality of the alloy is sound.

Lastly, do remember to de-gas before you make your castings. The oils and residual carbon in the heads will make this essential.
It all sounds daunting now but I think it worth while. And you know, nothing ventured nothing gained. Report back to this site as I think this may be of interest to many here.

Good luck, John.

 

YES you can. It still amazes me how I can grind a "weak point" on a large square ingot and take sledge hammer to it. Still some wonder that I can still do it physically too! Something satisfying about it for an unfathomable reason. John.

 

That will be experiment no.1 Mark. Thanks for the idea. I should be able cut an inch or so into them with a grinder, then I’ll give them an introduction to a 12lb sledge (it was my fathers from his days in a colliery blacksmiths shop).

Thanks for the advice John. I’ll remove what I can and clean them as well as possible, but I’d imagine they will still have a fair amount of contamination in oil passages etc, plus any ferrous bits I can’t remove.

I was thinking about pouring them as ingots as a first step. I read earlier that re-melting cast scrap ingots can help with de-gassing?

your right, it’s a bit daunting, but I’m enjoying myself as I’m learning.

many thanks, Ian

 

I've got an even better idea for you Ian. Kelly will kill me or maybe remove me from this forum but...
Just going to have supper (tea in UK) will write shortly. John

 

Thanks Kelly. Simple tools I have many of, so punches and cold chisels will be used as suggested. Thanks for the tip with the table saw. That could also be an option.

I don’t think any of these will be Mag. I haven’t collected them yet, but I did have a look at them and they are all quite heavy. As you say, experience is priceless here. Hopefully I’ll learn to tell the difference without finding out the hard way.

thanks, Ian

 

The only issue I've seen with pistons is aging of the alloy: I've seen some products around the 20+ year age that have become fragile if handled a bit too heavily, where the break occurs you can see large fern-like silicon crystals in the break. We had to recast a part from a 25 year old machine that was sat on the bench a bit too heavily and the base plate casting broke. This was made from a mix of scrap pistons so it could have had anything in it. I don't know how true it is, that pistons in cars get heat treated every time they are run for an extended period. You could dilute with purer aluminium like electrical wire from old welders or powerline aluminium to lower the silicon content.

 

Will the same apply to the cylinder heads? I’m unsure if they will be the same alloy as pistons? But good advice. I could add some clean aluminium to the mix when melting the pieces of head.

I’ll have to find a source of ingot moulds or do people here generally fabricate their own?

cheers, Ian

 

It's only the pistons that can have this issue, not the heads, known as a "Hypereutectic" aluminium alloy with up to 19% silicon according to Wikipedia: https://en.wikipedia.org/wiki/Hypereutectic_piston

 

Differential expansion can work for you, if you heat up an aluminum head in an oven, the valve seats will literately fall out.

 

Excellent, I only have the heads, so not as much to worry about there. I’ll collect a few of the heads on the weekend.

 

Good point Rocco, thanks for that. I’ll see what I can come up with.

 

What we have to be alert to is the composition of the piston alloy does not change. Mechanical properties may well do after being slammed on the head a few million times though! Normality is restored upon re-melting. Sorry, I was going to teach Kelly how to suck eggs from a previous conversation but thought that I would review new content before I start rambling again.
Thinking about that, without dialogue and sharing stuff nothing will ever happen and progress stops. Not accepting the "you can't do that" syndrome also falls under the same umbrella I think. Example #1....
When I was little more than a grown boy I had an ongoing and urgent need to straighten/bend cast iron. I was local to but not a member of a fine institution, The British Cast Iron Research Association. They had been very helpful (off the record) to me in the choice of Cast Iron grades and the choice of best sand for purpose etc. However after being, I'm tempted to say lectured but that was not really the case, told that that option was "impossible" I went back to the "well watch this" challenge and continued to perform the act on a daily basis.
Maybe I should open chat about this as opposed to a private chat here. Just another ramble. I'll finish catching up on this topic and then reply to Ian. Maybe I should learn how to paragraph instead of bending iron!
John.

 

Correct! Maybe we should also differentiate between Magnesium alloys and aluminium alloys containing magnesium. The latter being much more tolerant of elevated temperatures. John
Same topic, keep away from aero components!

 

You will fall out with your wife too! John

 

FWIW, when I did it, I used a divorced friend's oven.