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Thats kind of like asking if pineapple or coconut is better. Depends on what your doing. They are just different and have different characteristics that make them better than the other in certain situations.
I am an average guy driving Detroit iron powered by iron blocks. I do not plan on building a supercar which requires $$$$ aluminium block/heads so the iron V6 stays in my truck and iron V8 stays in my car. If I were going to build up a muscle engine it would be a SBC based on a 350 iron block. What can't it do? 200 mph for 500 miles at Daytona or Talledega speaks volumes.
Put me down for iron unless it's a motorcycle engine. Harley had to eventually go aluminium in that regard as they were being killed off. I still prefer an air cooled 80s Suzuki GS in line 4 engine.
Those NASCAR Daytona, Talladega engines have an average lifespan of 600 miles.
The aluminum engines run at Daytona for the Rolex 24 hrs last around 3,000 miles.
Ford, GM, all the foreign co.s are using aluminum engines for endurance racing.
in other words these aluminum blocks have a liner, whether it is a steel liner, or a coating, there IS STILL A LINER in the block, not bare aluminum.
ok so where did i say that cast iron is better? the fact is that i didnt. and again, bare aluminum cylinder walls are not going to wear long, you were talking about coatings which is still a liner on the cylinder wall.
so again i am right.
i will say that given the opportunity, as i noted in my original post, if the rules allowed it, i would use aluminum blocks and heads for building an engine for the reasons i stated. but that doesnt mean that aluminum is better or worse than cast iron. just different.
Thats kind of like asking if pineapple or coconut is better. Depends on what your doing. They are just different and have different characteristics that make them better than the other in certain situations.
Audi's very successful endurance racing diesels have aluminum blocks, likely as difficult a test of blocks as you're likely to find, no steel liners either.
It will be awhile before engines from million dollar race cars trickles down to us. If you buy a diesel truck, you will get a cast iron block. These vehicles are designed to work, they are designed to be cheap because they exist in a competitive market, and they are deigned to last.
Aluminum with sleeves for everything else on the street. Drag racers running high boost still love iron blocks.
In terms of carbureted engines: You don't need an aluminum block to get a lot of benifits - just aluminum heads. You get the benefit of light weight and better heat dissapation, which allows you to up the compression without detonation.
Cast Iron block for ultra durability and a long life. The biggest problem with aluminum is that it's a delicate metal and once overheated, it can warp and crack leading to complete engine damage ( ALM heads are the perfect example of this). Plus aluminum is a softer metal and can easily break, and scratch if not handled properly especially on accessories parts like brackets, idle tensioners, water outlet housing, and even suspension components.
With modern cars being so weight conscious and automakers looking for every reason to reduce weight for fuel economy purposes. It doesn't make sense to put an all cast iron engine in a small lightweight vehicle. So a small aluminum 4 banger works in this case.
For older bigger heavier cars, the old cast iron big block engines like a Ford 460 a Chrysler 440, and a GM 428 and the celebrated Chevy 350 blocks were all bulletproof and reliable beyond what many people thought in those days. Could an all aluminum engine have worked back then? Who knows, due to high cost of ALM, and that maybe the engineering just wasn't there as far as building a reliable lightweight aluminum V8 for mass production.
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