advice on heads

[jamesheath]

Hi all,

Our engine assembly is finally progressing nicely.
The engine has the original 2 bearing splashfed crank, crack tested, ground and re-metalled. It has new pistons at +60 thou.
The inlets are slightly enlarged. I'm planning to use it with the standard side draught zenith, though I do have a pair SU carbs that I could use....
It's going in a special, but quite a period one. I was planning to use the orignal head, but I do happen to have a Supaloy head in good condition:
   
Is there any point in fitting the Supaloy? I'm not planning to use the car on Trials etc, at least not at the moment.....

Cheers,

James

[dickie65]

Hi,
The Supaloy head should be higher compression than the late Ruby Head which will help make the most of the engine.
As you are building a Special then the Supaloy would be the sensible choice.
The standard carb is not a bad option if its in good condition. If you fit the Austin 10 version you will have some gains in speed.

[Terry McGrath]

Supaloy heads, being fairly shallow, have a tendency to warp.

[Ruairidh Dunford]

I would use the Ruby head with a single SU.

That combination will give you reliable brisk running. Do check your larger inlet valves don’t touch the inside of the head.

[Alan]

I agree. The late Ruby head is just as good as most aluminium ones, with the added advantage they are less likely to warp or leak.

[Bob Culver]

Alloy heads for cars generally became fashionable ion the 1930s because of low octane petrol comp ratio was very limited. It was generally reckoned that wth alloy about another ratioo could be run without excessive pinging (example  the stock Ford V8) models)
With modern petrol the breathing limitation of side valves limit comp ratio before the fuel does, so the alloy heads of no real advantge. (In theory the hotter the head the more fuel efficient the engine is as less heat being conducted away!). The Ricardo patent style as lte Ruby was more or less universal to the last production side valves (Ford Pop, Studebaker Lark)

[jamesheath]

Thanks everyone.
I'll go with the original head then.
It keeps the under bonnet looking fairly stock...
I might start with the zenith, and maybe move to the SU if I feel the need....

[Alan]

What you could do is measure the iron head to see that it’s 1.5 inches thick and if so and therefore unmodified, get 60thou planed off it. If you have big valves you will want to check clearance.

[Chris Garner]

I agree with Terry about the warping. I've never been a fan but recently have been forced to use one in an engine I built for a friend who wanted to keep it. It took me several attempts before I was happy with it.
One tip - put it in the freezer overnight and whilst still frozen fit it and torque it well down. Remember to use a thin HC head gasket.