Sand Casting an air cooled head 1

[tdub13]

Background: I'm modifying a vintage 2T race engine (porting, intake, combustion chamber etc..) In stock trim, this motor needs better cooling.
I've found a cylinder head (sunburst style fins) that has more mass and more fin surface area, which I want to modify and duplicate in a casting.

I've also found a foundry that will cast this head for me for a minimal fee

My question is around the alloy that they use: 535 ALMAG. I copied this description from

http://www.lbfoundry.com/535-almag-aluminum-sand-casting.html

Aluminum alloy 535.0 is an aluminum magnesium alloy that does not require heat treatment to reach full properties. It has excellent corrosion resistance and machining characteristics. Milling and turning speeds are 4X faster than alloy 319.0, and 16 to 18 times faster than gray iron or malleable iron.

The anodizing rating is excellent and the color is satin white after anodizing.

The polishing rating is also excellent and the castings can be buffed to a silvery white color.

The weldability rating is poor and it also is not recommended for leak tight or pressure type applications.

Typically it is used for parts where dimensional stability and shock resistance is important, such as instruments. It is also used for marine hardware, ornamental fittings and castings where lighter weight and high strength is a prime consideration. Almag 35 is 10% lighter than average cast aluminum alloys, 64% lighter than gray iron and 69% lighter than bronze.


My major concern is that it's not recommended for leak tight or pressure type applications. Yikes! The wall of the combustion chamber will be at least 14mm thick. Should I go for it? Or is it a waste of time?

Thanks for any help or opinions! Todd

 

[tdub13]

Those are great suggestions. I've got a bunch of heads designed in solidworks, but I'm trying to stay in the spirit of old school engine building because I race Vintage MX. I do have a friend right down the street who could easily SLA my designs and I could have them cast. Or go directly to DLMS, but it would feel like cheating. I have ultimate respect for the old school pattern makers and their skills. I think that this head will have a little more "soul" if it's hand formed. The imperfections are what will make it perfect.

 

[FennLane]

Porsche 911s use an alloy with a relatively high Yttrium content and these heads have always performed well even on high boost Turbo charged engines.

I did have the Alloy designation but am struggling to find it now.

 

[RoarkS]

@FennLane, I would LOVE to see that spec. Everyone suggesting 356 or similar... are you sure about that? Doesn't 356 loose it's temper right at 350-375°F? I know it's used in liquid cooled engines all over the place, right next to Viton exhaust valve stem seals. but as far as air cooled with cylinder head Temps upwards of 500-550°F, 242 is the only thing I've seen used due to its high copper content picking up the temper temp. I've recently been looking at 4032 as a billet air cooled head... but can't seem to find high temp data for it.

 

[tdub13]

I'm still picking away at this project in my spare time. So please post up any suggestions you have for aluminum alloys that would be good for this application. Thanks!