Casting a cylinder head

[hammers]

Hi. I am interested in casting a cylinder head for a 4 cylinder car in aluminium. (Let's take the issue of this not being a beginner project as read, it's a longer term goal).

It will be pretty much a copy of an existing cast iron head that I will scan using a 3D scanner, clean up and enlarge to allow for shrinkage. The purpose is to reduce weight and improve cooling.

What is the best way to turn this into a mold? If I get it printed on a rapid prototype machine, can they print a material that can be used as in lost-foam casting?

CNC machine it out of foam? It would have to be done in several parts due to the water chambers and ports.

I'm not too concerned if it ends in failure, it will just be an interesting exercise. I'm going to start by casting some replacement trim parts, hammerforms, and so on, and hopefully work my way up.

Thanks

[Redline]

That would be very in depth procedure.Useing cores and greensand would be your best bet. Lost foam could cause some problems.With greensand you could use the original head as a pattern .Then you would just need to figure out the core for the coolant passages and the intake / exhaust ports.Its a lot of work but it is possible.Are you a toolmaker, because that is a ton a manual machine work to lay out and machine.Wow if a diy person figures all that out then we are going to be on Mars sooner than I thought!

[JerryFlyGuy]

I'd have to say it's a project to work towards. I think you'd have some problems using the original head as a pattern, depending on what it looks like.

I've seen an alum head cast w/ lost foam. I know it was lost foam because I could still see the beading in the casting from the foam. It looked like the foam was cut in slices and then assembled. The slices were ~1/2"-1" thick.
The slices would enable you to get the proper interior profiles you'd need.
If you used these in conjunction w/ some cores for your various coolant and oil passages it might work. Another thought would be to do the slices and then where you have interior features, you could fill them w/ plaster. Let the plaster dry and assembly the slices. When you pour the casting the plaster will preserve the passages you need and you can 'wash' out the plaster..

In the end there is only 1 way to find out
If your just banging around in your back yard, what do you have to lose right?

Jerry [I've not cast Alum YET.. but I will be w/in the year if not sooner ]

[hammers]

What about contraction if I use the original head as a pattern?
Won't my casting end up a fraction of an inch too small?

This guy cast his own engine for his superbike at home. Granted, he is an exceptional case, but it is possible. I remember seeing the video of him dumping the hot casting into a drum of water from his swimming pool.

http://www.advrider.com/forums/showthread.php?t=62090
http://everything2.com/index.pl?node=Britten%20V1000

[maquiza]

I have also seen heads from lost foam. And you are right, they slice it, so you can have all the inner holes. They coat it with a refractory slurry, let it dry, and then the same sand that you will use for the mold box is use to fill the inner holes.

[thuffner3]

Z-Corp has a machine that will print in a material ready for puoring your molten Alum into. I thinnks it's called Z-cast.
You can check out there web site under zcorp.com I think. http://zcorp.com/products/zcast.asp

[schemo]

Originally Posted by hammers This guy cast his own engine for his superbike at home. Granted, he is an exceptional case, but it is possible. I remember seeing the video of him dumping the hot casting into a drum of water from his swimming pool.

dumping a hot cast part into a pool of water will will cause havoc to the integerity of the strength in the metal. the part will end up with thermal cracks internally. best best to cool a part is to cool it as slow as you can.

[JerryFlyGuy]

Schemo, that depends on who you talk to. I've heard it said [and read it] that you should actually use water on an alum casting after its set [past the slush stage] as its lock's in the alloy better w/ less precitation of the various metals in the alloy. When you want to make a T6 treated alum, you heat it for like 9 hrs at ~100deg below its melting point and then quench it in water, this improves the grain structure and machinablility of the part. So, it all depends on what your doing. I've heard that castings which aren't cooled w/ water are very soft and difficult to get to machine well, and have low strength..

FWIW..

Jerry [I'm no caster yet, but I've done some reading on the subject]

[FPV_GTp]

Hi

Have a look at this website , there are some great pattern makers here in australia making some very nice Ford cleveland V8 heads and some exotic vintage car heads and blocks.

DMD Australia Cylinder Heads - http://www.dmdaustralia.com.au/head.html

DMD Australia Austin Healey 3000 Alloy Block Project Pattern Making Process - http://www.dmdaustralia.com.au/block1.html

DMD Australia Austin Healey 3000 Alloy Block Project Casting Process - http://www.dmdaustralia.com.au/block3.html

DMD Australia Austin Healey 3000 Alloy Block Project Machining Process - http://www.dmdaustralia.com.au/block4.html

DMD Australia Austin Healey 3000 Alloy Block Project Assembly and Testing - http://www.dmdaustralia.com.au/block5.html


These guys , from what i can tell are using the old method of hand making molds .

Hope it is of some help

cheers


PS: Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic!

[gonejunking]

I'll throw my 2c worth into this, as I am making a few repoductions of Riley heads.
You can use the head that you have to pull a mold from to learn the basic's of mold making. I was given a head to pull a mold off of, but I could not cut it apart, to see how the water jacket's were shaped. So I waxed up the head, and used RTV silicone to make a mold of the head. I made a mold of all 6 sides, then put the 6 sides together and filled the cavity full of wax. Now I had a wax cast of the head. With the wax cast, you now have the locations of the valves, sparkplugs, intake/exhaust ports, waterjackets at the parting surface, and combustion chamber. From here, I get a head gasket, glue it to my surface plate, take a plaster mold of the combustion chamber's, place them in the gasket, then start building the waterjacket, and the runners for intake/exhaust, valve guides.

When you get everything to fit, you put the 5 sides of your mold over your core build up, then pour more wax into the mold. When the wax set's up, remove the head from the mold. Look for defect's, then cut it up to see if your matl is thick enough around the waterjackets. From here, you have to scale it up, to offset the shrinkage in aluminun. It's alot of work, but it can be done!

I joined this group so I could get the info to build a 3 axes router to make moldmaking easier for myself. I just started ordering parts, and will post my build, and the moldmaking for the first head that I do.

Jeffrey

[acondit]

Originally Posted by gonejunking I'll throw my 2c worth into this, as I am making a few repoductions of Riley heads. You can use the head that you have to pull a mold from to learn the basic's of mold making. I was given a head to pull a mold off of, but I could not cut it apart, to see how the water jacket's were shaped. So I waxed up the head, and used RTV silicone to make a mold of the head. I made a mold of all 6 sides, then put the 6 sides together and filled the cavity full of wax. Now I had a wax cast of the head. With the wax cast, you now have the locations of the valves, sparkplugs, intake/exhaust ports, waterjackets at the parting surface, and combustion chamber. From here, I get a head gasket, glue it to my surface plate, take a plaster mold of the combustion chamber's, place them in the gasket, then start building the waterjacket, and the runners for intake/exhaust, valve guides. When you get everything to fit, you put the 5 sides of your mold over your core build up, then pour more wax into the mold. When the wax set's up, remove the head from the mold. Look for defect's, then cut it up to see if your matl is thick enough around the waterjackets. From here, you have to scale it up, to offset the shrinkage in aluminun. It's alot of work, but it can be done! I joined this group so I could get the info to build a 3 axes router to make moldmaking easier for myself. I just started ordering parts, and will post my build, and the moldmaking for the first head that I do. Jeffrey

You can section an iron head to get an idea of the water passages and the like but you can't use the original head as a pattern. You have to build a pattern that is larger than the original by the amount of the metal you are casting in shrinks on cooling. For aluminum we used 1/4" per foot (about 2%).

So if you use a head gasket as the basis for laying out your pattern when you cast the head it will be smaller than the original head by the amount of shrink. That means your head bolt holes, water passages, and combustion chambers will not be in the correct locations.

Alan

[jgro]

Take a look here: http://www.lindsaybks.com/bks8/chas2/index.html Steve Chastain goes through how he made a cylinder head for a flathead in his second book. Buy it, it's got some good info in it.

jgro