I was talking to a buddy of mine about the way that engines have changed over time. Neither one of us could come up with a good reason for doing what the auto manufacturers have done/did with their engines.

Why did the manufacturers start using aluminum heads on the cast iron blocks? That was always a source of grief - the head would inevitably warp and ruin the engine. Seems like it they stuck with cast iron it would have been
a) Cheaper (cast iron is cheap)
b) Would eliminate head warp due to having 2 metals in contact with each other
c) Only be about 50 lbs heavier.

Why did they decide to go this route? Or put another way, if they decided to change the head, why not the rest of the engine?

 

There are a lot of engines with aluminum heads and or engine blocks. Reliability all depends on how they design the cooling paths.

Many of the high perfromance cars have at least aluminum heads. Due to better cooling they can give a bit higher compression and more power. Also every hundred pounds of weight is about 1/10th in the quarter miles.

I used to be on a Chebby Impala site and there was a lot of discussion about the aluminum engines and heads used in the Camaros and Corvettes, the Imp had all cast iron. There are tens of thousands or even millions of aluminum head and engine blocks out there. Maybe the engineering has improved a lot. There was no worry about aluminum reliability and many SS owners decided to do engine swaps or at least head swaps for the benefits mentioned.

I think the bigger problem with Aluminum and iron engines is that the dissimilar metals can have worse corrosion. So you have to keep up on the antifreeze and I am guessing there may be some design features to help minimize this.

About the only common aluminum part you probably don't want is aluminum rods. I have read that these pound themselves to death in a street engine. Better to use iron or steel rods.

Just my opinions, based upon reading and owning a couple Aluminum block and or head engines over time, never had a problem due to aluminum.

Jim Henderson

 

The only problems I've seen with aluminum heads is when the person continues to drive after the 'check engine' light comes on.

 

The 50 pounds makes a difference in fuel efficiency, the heat dissipation quality of aluminum makes a difference as well, and actually, cracking is more of a problem than warping typically. Dissimilar metals can be a bit of an issue due to different rate of expansion, and the corrosion angle, but that is why the stretch torque head bolts became so popular. As mentioned, many performance heads are also aluminum.

 

The dumbest combination, leave it to GM, was the Vega aluminum block/iron head engine.

Jim

 

Hmm, okay. So really its a matter of heat dissipation improvements and maybe some weight saved - although I have a hard time believing a commuter car benefits from the weight savings.

What about ceramic engines. Has anyone ever taken a look at something like that? Seems like a ceramic engine would have benefits above and beyond metal for a commuter or passenger vehicle. Despite opinions to the contrary, engines are much more efficient when they can operate at higher tempretures.

 

Aluminum heads are less prone to detonation with higher compression ratios due to their heat conductivity. Most aluminum heads are also later designs, and have better flow to begin with. Aluminum really doesn't have more of a warpage problem than iron, it's more a flaw in the attachment system, and like has been said before, cracking is a much bigger issue.
Head gasket shear hasn't been a problem since the early 90's, modern hg's have a lubricating layer on them to prevent shear issues.
Aluminum head have been used since the 30's, maybe even before, on many different brands of vehicles with a decent track record. Ford even put them on the flathead v8s from 33-38 (and before anyone says they must have been aftermarket, look it up. I had one here with Ford cast into the heads)

 

Ceramics are around, in the exhaust and turbos of some higher end Europeans, me thinks. Not sure what the snag was on ceramics for everyday motors, but they were talked up a few years back as an answer for pistons, probably as a coating, and ports etc to hold the heat in the combustion chamber and exhaust to maximize power and turbo boost. Probably a cost issue.

The turd on a stick idea I recall was stamped steel engines....made up blocks with liners. And I think it was Ford working on it!!!

 

Those engines shoved Liberty Ships across the Atlantic and back, along with LSTs, and EMD locomotives used them until the early 90s when they went to four stroke engines.

 

Uh, I was talking about gas car engine "ideas" in the '90s, not Detroit diesels, if that's the "stamped steel" engine you're referring to???? If not, what was it?

 

Actually, Crosley made a stamped steel engine for a number of years. Never heard a Crosley referred to as 'durable', though. As far as weight savings goes, engineers constantly look at the whole car to trim weight. Many car components have been put on diets over the years. Then they go and put more and more powerful engines in 'em. Go figure!