A billet aluminum block is best- but this is also the most expensive.
Aluminum blocks have been around for some time not, how to sleeve or treat the friction surface for the rings has been the problem. The way aluminum age hardens and reacts to high temperatures is much different from iron.
Some sleeving techniques work very well others don't!
But any good machine shop will know how to sleeve an aluminum block the right way. Cylinder sleeves have been around for a long time and over the years the problems have been pretty much solved.
Aluminum is lighter. Sleeves solve the durability issue. Aluminum rejects much more heat than an iron block; so the thermal efficiency is lessend. Aluminum can suffer embrittlement from heat cycling. Cast iron retains more heat and would therefore ultimately make more power...this might be useful if you were going to run a steady diet of E85 thru the engine. The alky burns cooler and cast iron helps retain the heat to vaporize the fuel.... You'll see a number of racer's use cast iron heads on an alky engine just for the heat retention.
Cast Iron is very heavy, and it rusts. Aluminum is actually more durable, since it doesn't rust. The cylinders are sleeved with steel in an aluminum block. It also has better heat transfer.
Sure cast Iron rusts but that actually seasons it and makes it stronger. Aluminum is lighter and has much less Tensile strength. however good engineering overcomes this inherent weakness. most cars today do have either aluminum block or heads or both.
The EUROPEANS once again are LEADERS with ALUMINUM ALLOY BLOCKS! It is NOT a good idea to use CAST IRON liners in an ALUMINUM block like GM does with ECOTEC engines! THe LINERS over time can L|SLIP and TURN as engine ages or overheats JUST ONCE! THis problem is REAL! <
Aluminium is lighter by about half but is softer so need to be lined or use a special alloy, usually Nikasil (Nickel Silicon Carbide) or Alusil (Aluminium Silicon Carbide).
Volkswagen air-cooled engine have used magnesium for years, it makes for light engine blocks, and no thay don't catch fire.
What exactly are the pros and cons of each? Wouldn't cast iron be more durable?
