Casting my own aluminum head

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Seff
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Casting my own aluminum head

Post by Seff » Sat Nov 21, 2015 11:58 am

Born by the discussion here: viewtopic.php?f=8&t=265298

Goal: More power and more fuel economy (through the use of an overdrive unit coupled with the higher power).

Done through:
- Higher volumetric efficiency
- Better/more complete combustion

Limiting factors
- Flathead design
  • Head material: Cast iron has a thermal conductivity of 55 W/(m*K). This is rather poor, and means that cast iron has a hard time transferring heat from the chamber to the coolant, making for hot spots in the chamber, which cause detonation if compression is too high. This in turn is one reason why compression is traditionally kept low.
  • Flow: Air-Fuel mixture and exhaust gasses have to pass through a U shaped channel, and through the choke point of the combustion chamber. This impedes volumetric efficiency.
  • Flame propagation: The combustion chamber is long and irregular with the spark plug in one end, which causes the combustion to push air and fuel in front of it as the piston is pushed downward. This causes detonation of the unburned air-fuel mix. To prevent this knocking, compression is traditionally kept low in flatheads.
  • Chamber size: The combustion chamber is long and irregular with a huge surface area relative to the chamber volume. This has one of two effects - either the chamber surface leads to a lot of heat dissipation (and thus energy lost to the cooling system), or hot spots. Thus compression is kept low.
  • Valve placement: Due to the valves at the edge of the chamber, the chamber can't be made smaller in that end due to the risk of shrouding of the valves.

Proposed solution
  • Head material: Aluminium has thermal conductivity of 204-250 W/(m*K). This is, in the worst case, four times as efficient as cast iron.
  • Flow: Porting of the exhaust and intake runners should be easy - hogging out the intake isn't productive for making low-end torque, but the exhaust should flow as freely as possible. Larger valved runs the risk of more excessive shrouding - so none of that so far. Relieving of the block between the cylinder and the valves(the transfer area) shows limited results only, whereas raising the roof over the transfer area makes good power in flatheads. This should be compared to the lowered compression caused by a larger chamber.
  • Flame propagation: Shortening the combustion chamber overall length could minimize the effect described above - notice the difference between this original head and its chamber design and this "high performance" head - the original head has a chamber that extends up to 40% into the cylinder diameter, whereas the HP head has a far more "square" chamber (extending less into the cylinder diameter), promoting a more uniform and faster combustion. This, in turn, makes for less tendency to detonate, allowing for more compression. Theoretically. The compromise is of course the transfer area, that means a perfect circular chamber cannot be achieved.
  • Chamber size: See above:
  • Valve placement: Not a darn thing. :lol:
Casting ideas:
  • Baked plaster of Paris with 20% talc added in to prevent cracking, which has been baked to prevent exploding of the casting. Ideally the mold should be multiple use.
  • Water jackets; three ideas:
    1: Solid casting with drilled-out water jackets. Takes time, only allows for round water jackets that can be drilled from the outside of the head somewhere. Risk of cracking the casting or drilling through the casting.
    2: Two-piece casting: Allows for very detailed water jackets, but complicates the process since the mating surfaces need to be machined. Possible leaks around the spark plugs.
    3: Cast-in water jackets - hard to make in the dimensions needed by the size of the head, a risk that the material is stuck in the casting. A new water jacket negative would have to be constructed for every head casting.
Problems so far:
  • How big are the stock water jackets in the head? I need to find out whether aluminum benefits from the same size water jackets, or whether it benefits more from thicker material and less water jacket volume.
General thoughts?


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Re: Casting my own aluminum head

Post by Wolfman » Sun Nov 22, 2015 6:48 am

Fascinating !
I have never considered such a thing. But along the same line, I just worked on an early 50s Pontiac straight 8 engine. While looking for parts, I discovered there is a wealth of intel available on these engines being built up for racing use. A lot of this being the same as you are suggesting for the L-134 and both are flat head engines. You might check out that aspect.
You plan to do your own casting ? That is an art in it's self.
I have a good friend that was into show cars and had a top fuel funny car at one time.
He got interested in Bonneville speed records and bought the forms and a set or two of partially and finished hemi head conversion for a flat head Ford. The engine that held the world speed record back in the 50s. An awesome accomplishment. The forms were made from Walnut. A beautiful piece of work in themselves. He had some serious health problems a few years ago and has sold it all. :cry: But he is still going.
My next question, where you headed with this ? Sounds time consuming and expensive. Anything like this requires a lot of experimenting. What looks good on paper ends up in the scrap heap a lot.
Also seems like a lot of work for what may give a little performance boost. An L head is not the most efficient design. Why you don't see them in use anymore.
Building any kind of performance engine is a package deal. You can't just change one part for best results.
Obviously, you are more than an amature or at least have done your home work.
Be interesting to see where this goes.
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Re: Casting my own aluminum head

Post by Seff » Sun Nov 22, 2015 11:36 am

Hi
Thanks for the interest.
My knowledge of flathead hotrodding potential was indeed gained from reading various flathead performance forums and guides. It's all theoretical knowledge at this point, sadly.

My casting knowledge isn't great, but then again; you don't waste metal, you just melt it again at try once more. No waste of materials means no waste of money.

Walnut forms? The piece you shape the sand or plaster around, or the mold you pour the aluminum into? I'd think that walnut would burn.

I'm heading towards more low-end power so I can run a higher gear without lugging, leading to improved fuel economy and improved power. The second goal is learning to understand engines a bit better - plus, I study Automotive Technology, so it's school relevant.
The L head is indeed a very limited design, so the true goal is: taking advantage of modern fuel to make more power and/or better economy.

As you rightly say, it's a package deal. I'm reluctant to dig too far into the block until I've made sure the head won't explode when run. At that point I would start porting and otherwise improving flow. Maybe even a new/reground cam.

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Re: Casting my own aluminum head

Post by Wolfman » Mon Nov 23, 2015 6:26 am

The walnut form was to form a sand casting. The walnut was in the shape of the head. Once the sand was formed, the walnut was removed, leaving the shape in the sand casting the metal was poured into. Walnut, a hard wood, was used because the wood was easier to work with than metal and still held up for the limited run of heads that were cast. Once the casting was formed, the sand was knocked off and the metal head removed for machining. A one at a time thing. Not for mass production.
Volumetric efficiency on an L head design is pretty bad. Since the valves are to one side instead of overhead, any increase in valve opening, duration and overlap along with the inertia of the escaping exhaust gas that would improve volumetric efficiency pulls as much incoming fuel and air from the intake, out the exhaust as into the cylinder. The valves are next to each other. The cylinder is to one side. Split manifolds with larger ports as well as headers helped but was only affective to a point. Here again, this approach is for maximum performance and at a higher RPM to improve maximum horse power. Not what you are looking for. You say you want better low end torque. I would think more lift would be most effective at low RPM.
An increase in compression would help. There is a high altitude head for these engines that would improve low end torque. Taking advantage higher 89 to 93 octane fuel used oday over the 68 octane used back in the day, makes this a good approach. Increased timing with the higher octane fuel would also help.
IH had a Horse power issue with their C-60 cub engine. The low compression, L-head engine used cast iron, flat top pistons. An 8 HP 4 cyl. :roll:
One of the answers, they replaced the flat top cast iron pistons with a lighter, domed top aluminum piston. The dome was to the valve side, not in the center and reduced the combustion chamber volume, increasing the compression ratio. A simple up grade and produced about a 50% HP increase. 8 HP to 12 HP.
Never seen anything like this for an L-134 but if you are going to make something, it is an option and more suited to the results you are looking for.
Milling the head would increase the compression ratio and be simple to have done. Not sure how much you can safely take off. ??? Maybe someone else knows.
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Re: Casting my own aluminum head

Post by Seff » Mon Nov 23, 2015 6:41 am

An interesting read!
Thanks for the tips on casting procedure. One at a time is what I'll be doing until I've perfected the design. I doubt there's even a real market for these heads.

I agree with all you've said about L head modifications, and about the RPM focused modifications not being my goal. Easier breathing is never bad, though.

The pistons you describe sound like pop-up pistons. I haven't been able to find such things either, nothing in the 3.125" diameter the factory bore is.

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Re: Casting my own aluminum head

Post by lt.luke » Mon Nov 23, 2015 8:58 am

Someone like Lunati will custom grind cams, will someone. Like Sealed Power or Moog custom build Pistons?

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Re: Casting my own aluminum head

Post by Seff » Mon Nov 23, 2015 9:27 am

I would think a custom ground cam requires only that you reprogram the grinder, whereas new pistons need new machining or maybe new casting molds?

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Re: Casting my own aluminum head

Post by lt.luke » Mon Nov 23, 2015 11:13 am

Seff wrote:I would think a custom ground cam requires only that you reprogram the grinder, whereas new pistons need new machining or maybe new casting molds?
I didn't say it was easy. But they would have a lot of the technology already in place which might cut the costs.

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Re: Casting my own aluminum head

Post by Seff » Mon Nov 23, 2015 11:31 am

Absolutely. Hey, asking is (normally) free.

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Re: Casting my own aluminum head

Post by lt.luke » Mon Nov 23, 2015 11:36 am

Seff wrote:Absolutely. Hey, asking is (normally) free.
That's funny!

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Re: Casting my own aluminum head

Post by lt.luke » Mon Nov 23, 2015 11:38 am

Thought... Might be a bad one. The poster said nothing with a dome shape is availible in a 3.25" diameter, but I wonder if another (larger) piston could be turned down to the appropriate 3.25"? 3.33" could be an option of the OP punched his block .080 over, which I've heard mixed reports that is possible.

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Re: Casting my own aluminum head

Post by Seff » Mon Nov 23, 2015 11:59 am

Well, here are stock replacement pistons for the L134. That shows a compression distance of 2.167". Filtering for 3.125" bore pistons gives us no other usable pistons. Filtering for 3.130" and 3.135" bore gives us nothing with close to that kind of compression distance. The L134 pistons are pretty old-fashioned.

It looks like someone like Arias make custom pistons. But they're expensive like hell, of course.

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Re: Casting my own aluminum head

Post by bazza46 » Mon Nov 23, 2015 1:03 pm

Why not try to obtain a Kaiser Supersonic head? It'd be a lot easier and probably not as expensive as you think. It raises compression, improves fuel flow and transfers heat so much better and it's been the result of much effort and research on the part of engineers.
The quickest and easiest way of increasing an engine's power (apart from supercharging), is to raise the compression.
Any increase in compression in a side valve engine has to be obtained by reducing the combustion chamber volume on the valve side, as the pistons already go to within the gasket thickness of the pistons to produce a 'squish' area, which improves combustion spread.
Just my thoughts.
"The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt"..Bertrand Russell

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Re: Casting my own aluminum head

Post by Seff » Mon Nov 23, 2015 1:27 pm

Well, I DO have a wanted ad up for one, but it seems so very simple that it COULD be made in my back yard.

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Re: Casting my own aluminum head

Post by Wolfman » Tue Nov 24, 2015 6:12 am

Your back yard sounds like an interesting place.
Back to more cam lift, one way to get more is, re-profile the cam lobe. Instead of trying build up and regrind the cam lobes, leave the high point of the lobe as is and grind the rest of the lobe. Readjust the valve clearance and you have instant lift. Does not change the over all profile, just more lift. An old racers trick.
You still need to find someone that can grind the cam. Never heard of an over the counter performance cam for an L-134.
Reducing the combustion chamber volume has it's down side. The combustion chamber on an L head is the only path for the air/fuel mix to enter the cylinder.
A smaller chamber to increase the compression could also be a restriction to flow.
Back to the Farmall C-60 pistons. One of the advertised improvements was the "dome" caused turbulence in the cylinder, giving better fuel mix dispertion in the cylinder and improved combustion as well as higher compression.
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