Cylinder head aluminium v Iron

[shane]

I would be grateful for opinions on the performance difference that can be expected from using a Dave Dye head compared to a Ruby head with appropriate mods.

Any detailed information on modifications would be appreciated.

I have had conflicting advice on the benefits and would be grateful for further opinion.

[Chris KC]

My tuppence worth is whichever you choose, don't go above 6.5 compression ratio for a road car with a standard bottom end.

[Reckless Rat]

I believe the location of the spark plugs is better on the Dave Dye head compared with the Austin one. General combustion chamber design is roughly similar, but the Austin one is prone to oiling plugs if the engine is a bit worn. Performance wise I think they'll be roughly the same.

[JonE]

The Ricardo LOOKS like it will perform better! And can be machined for slightly lower compression variants. It also saves you one gasket/water leakage point.

[Steve Jones]

The combustion chamber design on the later HC Austin head is pretty good but the head has one, fundamental, flaw as noted, above, by Bruce. That is the position of the plugs over the edge of the cylinder bore. If you have any oil coming up the bores than these heads have a tendency to oil plugs. If you've built your engine correctly then oil shouldn't come up the bores and past the rings but even on a well built engine, over time there inevitably will be wear. The Ricardo heads also have a good combustion chamber design but have the plugs positioned over the inlet valves well away from the bores. Other advantages of the Ricardo head include it being a late 1920's design (important in some applications) and the integral top hose connection means one less potential leak point.

Putting my money where my mouth is, I've five Austin 7 engines and four of them have Ricardo heads (the fifth is a bog standard engine in a very standard car). You pays your money and you makes your choice but have a look round the paddock at any event with a number of competing Sevens and these days, you'll find the majority have Ricardo heads.

Steve

[Reckless Rat]

Austin head here:



You can just make out the shadow of the cylinder bore and the plug hole is right on top of the outer edge.

As a point of note, my 33RP has this head fitted and has run without problems for several thousand miles. The difference in torque compared to the Low Compression head is impressive, but you need to be wary of ignition advance if you're using an Austin crank... discretion is advised!

I use B5HS plugs.

[Chris KC]

I've never experienced plug oiling with a '37 head, or perhaps I'm just too thick to notice it. Or maybe I've been lucky.

What I have done though is warp an alloy head like a Smith's crisp through an overheating incident (several hundred miles from home), which is why I tend to prefer cast iron.

I'd suggest using a corrosion inhibitor with one of these alloy heads, as replacing the outlet branch seems not to be an easy option.

[shane]

Sorry, I should have been clearer on the spec the engine will be for race use but I  am trying to modify or use original components anywhere they are visible but not at the risk of performance.

I have phoenix crank and rods slipper pistons, Paul Bonewell race camshaft and lightened and balanced flywheel.

[Alan]

I’d use a ‘37 head. Machine 60 thou off the face and radius the combustion chamber where is overlaps the bore. Check that there is enough valve clearance. With slipper pistons it should be fine.

[Charles P]

I have a machined 37 head on my car. Oiling plugs is very rare.
I've always suspected the folklore about the tendency to oil plugs comes from the days when the standard of engine rebuilding was "it'll do"

c