300TDi Cylinder Head in Cast Steel

[Boydie]

Just out of curiosity but how many 300TDi owners would be interested, seriously interested, in buying a cast steel cylinder head for their engines?

I was chatting to a patern-maker mate of mine while we were sucking on a few beers and looking at a spare "evolution" cylinder head I have in my "man shed". He was of the opinion that he could reproduce it in steel with improved waterways as the steel would'nt be prone to cracking and would naturally take greater combustion pressures, not that I'm interested personally in upping the boost from the standard 14.7psi. but the improved cooling does interest me as well as the reduced risk of cracking.

The current cost for a new head, complete with valve guides and valve seats here in Oz is arround AUD $1250.00, - which is what I paid for this spare one, the steel one would be almost double that (arround AUD$2000.00) but would be virtually indestructable, the down side, apart from the cost would be the increased weight, almost double the standard alloy one. I would need to have firm commitments for about 50 of them to make the casting worthwhile and for the price to be at this level, a one off would be enormous !!!

As I listed in a previous post I had the three triangular water-ways in my engine block TIG welded up to increase the plane between the cylinders, these waterways are not mirrored on the head so they are to all intents and purposes redundant, I dont understand why the cylinder head gasket has the cut-outs to match the block and I "filled" them in with red high termperature gasket material when I fitted the head, the engine has now done well over 25,000 kilometers with no problems so I guess it works.

[Phil Hancock]

Are you sure the head is actually steel and not SG iron? Some steam loco cylinders needed casting a few years ago to replace the original steel castings which were long ago scrapped, British Steel Corporation(remember them?) were going to do the castings and said that they could not guarantee the castings to be without defects, but if they were cast in SG iron it would have the mechanical properties almost of steel but be easier to cast as the metal is more fluid when molten. They also said that back in the day that it was a regular occurence to do weld repairs on the steel castings before they went for machining. These cylinders were a lot larger and noware as intricate as a cylinder head for a little diesel.

[Tanuki]

"Steel" is a very wide and flexible descriptor - unless you specify the precise alloy involved along with the processes used it's impossible to guess what the characteristics of the resultant object will be. And, TBH, the characteristics of steels are rather inappropriate for cylinder-head duty.

If given the choice between a [cast-iron|steel] cylinder-head and one made from an appropriately specified aluminium-alloy, I'd go for the aluminium-alloy one every time - because its thermal-conductivity characteristics are predictably better. You're not looking for fatigue- or tensile-strength [which is where steels are good] in a cylinder head.

[Spongie]

If given the choice between a [cast-iron|steel] cylinder-head and one made from an appropriately specified aluminium-alloy, I'd go for the aluminium-alloy one every time - because its thermal-conductivity characteristics are predictably better. You're not looking for fatigue- or tensile-strength [which is where steels are good] in a cylinder head.

Have to agree going like for like casting isn't really a great idea due to the inefficiency of steel for thermal conductivity you would be wanting larger and more cooling ports.

Currently the tdi uses the aluminum head as a secondary radiator. All the hot alloy dissipates heat into the air faster than the cast iron block. Conversely it also dissipates more into the coolant too.

[honitonhobbit]

The big difference in reliability between the 200 and 300tdi heads is the quality of casting. The 200 was a flipping expensive engine to produce (in car profit terms) and the 300 was always designed to save costs. The head casting on the 300 is nowhere near as good as the 200. Better to cast a 300 Head in Ali but tidy like

[Boydie]

The material John nominated was melted down engine blocks with additional carbon. Due to the improved strength of the head the water-ways would be increased, (as I said he wasnt impressed with the "evo 2" new one I have). For example he cut down an old distorted one I had as a door stop and the thickness of the base (above the pistons) is massive - almost 5/8" in steel form would only need to be 3/8" to handle combustion pressures well over the standard 14.7psi,

Anyway, from the general response here on the forum I guess its another pipe dream

[Phil Hancock]

As engine blocks are cast iron and you proposed adding more carbon that does not make steel, you want less carbon to end up with steel.

[Boydie]

????? Phil. Engine blocks are normally made from fine grain mehonite (spelling??) as are disc brakes, as such they are not cast iron but low carbon steel. But I'll take a small cutting off my spare block and have it tested.

Cast steel is a lot lighter than cast iron and has a far finer grain, its also stronger and is far easier to machine. Cast iron is heavy, large grained and woefully poor to machine and tap, its camparitivly "soft" and would need to have liners in the cylinders.

One of the main attractions with a non-alloy head would be the lack of possible corrosion, especially arround the infamous "P" gasket.

[Phil Hancock]

Whenever I have done or seen done any machining to cylinder blocks, heads, brake disks or drums the swarf, dust and smell/taste of the dust says to me cast iron. Meehanite is cast iron. Google it.

[Boydie]

Phil, thats a bit like saying stainless steel is steel and that titanium is just another alloy.

True cast iron is brittle and has large granules and wears easily, meehanite is a refined cast iron with smaller granules to improve its thermal properties (as in disc brakes) and because of the smaller granules it's easier to machine - the smaller granules also make the compound stronger.

The last rtue cast iron object that I can remember seeing was my late mothers Singer sewing machine table legs and treddle.

[Phil Hancock]

Yes the 'traditional' cast iron is brittle, but cast iron comes in a lot of grades that will vary massively in their properties and uses and have done so for many many years, IIRC a series petrol crankshaft was SG iron as an example as was the crankshaft in my old pre WW2 designed truck. Adding extra carbon to any grade of cast iron when melted does not make steel as steel has less carbon content than CI.

Simply put Molten iron + Bessemer convertor to burn out the extra carbon = steel.

Cast iron family carbon content 2.4% to 4%

Steel family carbon content, up to 0.3% for mild steel going up to 2% which is high carbon tool steel.

[Boydie]

. obviously we could have a full on discussion on this toppic, and like most engineers still not arrive at an agreement - thank goodness there isnt an accountant involved in this thread to mess it up. suffice to say that an acceptable definition of "steel" is an alloy of iron and various other materials and chemicals as against pure iron in a cast form.

[Phil Hancock]

You are not now throwing wrought iron into the pot now are you???

[Boydie]

Nar Phil, I've contracted John to make me one up, I will pay for and own the moulds (at considerable cost) but enough said. While alloy is certainly a lighter material and a better medium for heat transfer it corrodes farfaster than cast steel and unless you go to very expensive and sophisticated alloys as in titanium its weaker and softer. Most of the existing design hassles "P" plate gasket etc. we will redesign along with better exhaust porting and exhaust manifold to bring the turbo in at arround 1100 instead of 1800 RPM. With the cast steel head, leaving the boost at 1 bar.the combustion areas can be a lot thinner and this equates to more water in the head and better water flow, I'll keep you informed. ETA is 20 weeks.

[Spongie]

Have you tried on AULRO more likely to have uptake locally to be fair

[Boydie]

Yes Spongie, been there, done that and the cost puts most people off, understandably so too.

My interest is mainly in the engineering aspects of what it should be and could be so I'll press on regardless and if its a better head then I'll see if others are interested. From my aspects this will be more fun than I had in the late 60's when I worked as a combustion engineer at Aston Martins when they were at Newport Pagnell just before I emigrated to Australia.