Difference in expansion rate between iron sleeves and aluminum block? That's a non-issue. Here's why: Iron sleeves have a smaller coefficient of linear expansion than the aluminum block, but they are closer to the fire. The block for the most part is a little hotter than the coolant, and the sleeves are hotter than the block. Those temperature differentials have to be there for the heat to flow out of the cylinder.
How would an iron cylinder that didn't expand as much as an aluminum block cause oil burning? That's hard for me to see. The reason that we have to run several thousandths of clearance between the aluminum pistons and the iron blocks is because the piston expands that much more. So unless you have an iron piston running in an aluminum bore, the hotter the engine gets the less clearance between piston and cylinder, meaning there is less chance of oil escaping.

Also, think of all the millions of aluminum block engines that have to pass emissions for 100,000 miles. If they tended to become oil burners they could never be certified, never be sold at all in the USA.

So here's the real issue - Money and weight. A stock 440 block weighs something like 220lb. A cast iron aftermarket block, at least the World Products cast ones, weigh 320 lb. An aluminum block may weigh 120 lb. So going from the iron to the aluminum aftermarket block will take about 200# off the front end of your car. That's quite a bit less mass to try to steer, accelerate and brake. If you can afford it, it's the way to go in my book. Add in the repairability of aluminum over cast iron and it's quite an advantage.

Sure you don't NEED it, but most of us don't NEED more than Slant 6 type power to get our cars from pt. A to pt. B, either.

R.