Dissimilar metals and warm-up time

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I was thinking about warming up engines and it seems if you have a iron lock and aluminum heads then you should be more cautious and have a slow and lenghty warm-up. But if it is all aluminum, you are probaly okay to leave out quickly if you dont hammer down too soon.


Im not too sure about iron head/iron block engines.
 
Iron blocks and aluminium heads are more at risk from overheating.

It's the pistons and cylinders that are a bigger issue, specifically aluminium pistons in iron cylinder sleeves.

Aluminium expands more than steel with temperature and, of course, have much less thermal mass than the engine block so they heat up faster. You could, potential end up with a situation where the piston expands enough to get too tight in the cylinder.

I'd guess you'd probably need an engine on the tight end of the tolerance spectrum, a very cold block and then have to start it and go to full throttle at full load for an extended period to get close to any issues with any modern engine, so if your driveway is directly on a particularly long and straight stretch of the Autobahn be careful!

It's more of an issue in two strokes where the rings have to go past the exhaust ports and can catch on the edge of the ports if you're too aggressive with a cold engine. Even then, it doesn't seem to be an issue with modern snowmobiles, more with the two stroke motorbikes of the 70's from what I've heard.
 
All-iron engines are the most durable, hands down. While full aluminum designs can have their weaknesses, iron block/aluminum head engines don't have to take a backseat to any other types until it comes to being overheated - design is a greater factor than material. The Buick 3800 is darned hard to hurt, while the 3.1L used in similar cars is known for head and head gasket issues. The Vortec 350 is another pretty stout design, while some of its predecessors with iron heads are known for cracking because the "lightweight" design castings were too thin. Jeep's 4.0 six started developing more top-end problems when they tweaked it for the high output version - both fully iron engines, just a redesign that didn't quite work out.
 
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Originally Posted By: Wikipedia
The AZ series uses an aluminium engine block with cast iron cylinder liners and aluminium DOHC cylinder heads.

The cylinder block is an open-deck, midi-skirt die-cast aluminium type with cast-in iron liners and a die-cast aluminium lower crankcase and a stamped oil pan. The forged steel crankshaft is fully balanced with eight counterweights and supported by five main bearings.

https://en.wikipedia.org/wiki/Toyota_AZ_engine
What does the above quote mean? This is a very common toyota 2.4l 4 cyl engine used in Camry's, Rav 4's, Solara's and Highlander's. Is this a bad design that's prone to overheating? I do know that quite a few of these burn oil.
 
To many variables here to get to a correct answer. Temperature for example is it cold out, is it hot out? What weight of oil is in the engine? Are you running antifreeze? Do you plan on " revving" the engine after starting? In most cases I would recommend not "warming" up with either style engine, but a nice easy going drive to temp. Engines are designed to work under a load. Aluminum heads come in as a big factore when it comes to overheating and compression, which is a whole other story
 
I know that banging on a Cummins 6.7 when cold is a good way to lose a head gasket.

Has a lot to do with the overall design of the engine, and not simply materials.
 
I was amazed when I bought a vehicle with an all aluminum engine compared to the all cast iron engines I was accustomed to. The quick time it takes the aluminum engine to warm up is unreal. I have a feeling the cast iron engine will out live the aluminum engine though, and if a rebuild is ever needed be a lot cheaper and easier to do.
 
Originally Posted By: THafeez
Originally Posted By: Wikipedia
The AZ series uses an aluminium engine block with cast iron cylinder liners and aluminium DOHC cylinder heads.

The cylinder block is an open-deck, midi-skirt die-cast aluminium type with cast-in iron liners and a die-cast aluminium lower crankcase and a stamped oil pan. The forged steel crankshaft is fully balanced with eight counterweights and supported by five main bearings.

https://en.wikipedia.org/wiki/Toyota_AZ_engine
What does the above quote mean? This is a very common toyota 2.4l 4 cyl engine used in Camry's, Rav 4's, Solara's and Highlander's. Is this a bad design that's prone to overheating? I do know that quite a few of these burn oil.


Its a good engine, they use an iron liner instead of an etched bore which is a good thing, if its designed properly an all aluminum engine will last just as long as an pig iron engine, for ultimate durability a high nickel or silver iron is the most durable and the most expensive. The engine uses a well supported forged crank so it has the right internals, the only soft spot is the open deck design.
Open deck engines are not as rigid in the bore areas as closed deck blocks and are more susceptible to head gasket leaking, sealing this type of block poses real sealing issues for the gasket manufacturers. Unlike Subaru Toyota seems to have got a handle on it but IMO the engine would have been substantially more stable if they went closed deck. For unmodified engines its probably not a big deal in daily use.

A good example is the Subaru EJ 22 and 25 engines the 22 was closed deck and the 25 was open or semi open, the open deck was notorious for blowing head gaskets while the 22 went seemingly forever. This video is informative.

http://www.enginelabs.com/news/supporting-your-cylinders-open-semi-closed-or-closed-deck/
 
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Iron blocks and aluminium heads are more at risk from overheating.

It's the pistons and cylinders that are a bigger issue, specifically aluminium pistons in iron cylinder sleeves.

Aluminium expands more than steel with temperature and, of course, have much less thermal mass than the engine block so they heat up faster. You could, potential end up with a situation where the piston expands enough to get too tight in the cylinder.

I'd guess you'd probably need an engine on the tight end of the tolerance spectrum, a very cold block and then have to start it and go to full throttle at full load for an extended period to get close to any issues with any modern engine, so if your driveway is directly on a particularly long and straight stretch of the Autobahn be careful!

It's more of an issue in two strokes where the rings have to go past the exhaust ports and can catch on the edge of the ports if you're too aggressive with a cold engine. Even then, it doesn't seem to be an issue with modern snowmobiles, more with the two stroke motorbikes of the 70's from what I've heard.
That's about dumbest summation I've heard of, iron block aluminum heads are some of the longest lasting engines in the world, you totally ignore there's an engineered head gasket between them.
 
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