I have a real question about Aluminum engine blocks. Why don't they work in an HD truck? I keep hearing how it would be great to get an steel block in a GM 6.2 to put in a HD truck. GM puts these in the NHT halfton Silverados with upwards of 12k tow ratings. Why won't they work in a HD truck with 10-12k lbs tow rating. Does the block warp and deflect under load once you put it in a HD chassis? (Serious question) I just want to know. We have aluminum heads in HD trucks, what is wrong with aluminum blocks?Thanks!Jeremiah

In our vehicles, we've had cast iron blocks with cast iron heads, cast iron blocks with aluminum heads, aluminum blocks with aluminum heads. We haven't had a problem with any of them. I would say modern manufacturing and design has overcome any problems with aluminum blocks or heads many years ago. Years ago I recall the GM Vega aluminum block had a number of problems. But that was back in the 1970's and we've come along way in design and manufacture since then. As you mentioned the GM gas engine, remember that the heavier duty GM Duramax diesel engine has aluminum heads and block. I can't recall any issues arising from this engine, due to the use of this material. I think those that maybe concerned about the use of aluminum engine blocks....might be basing their opinion, on older ideas about the unsuitability of aluminum as engine block material, that was prevalent during the days of the problem prone Vega aluminum block. Nowadays, not an issue, IMO.

Aluminum blocks are more likely to suffer damage from overheating. Aluminum also looses about 20% of its strength at temperatures over 200 degrees. Aluminum costs about four times what iron does. There's also problems with contamination of coolant. It turns acidic over time and is rough on aluminum. I think that we've made a lot of advances in alloys over the last few years and I won't be surprised to see more aluminum used in engines as the big three struggle to meet fuel economy standards.

You answered your own question; they twist around like a snake with his head stepped on. Even iron blocks twist around and that's why we have engine plates when we race them. Hard to believe but they will distort and twist and crawl all around. :EThen there is the growth factor. Ever see how much aluminum grows. I forget the figures but a 747's wing span is like a foot longer sitting in the sun than in the shade. :ETake that down to a bearing with only 3 thou clearance and see how hard it is to control bearing clearance. Chevy did an outstanding job with the LS engine but it's still not good enough for HD work. :(Power and duty cycle are two entirely different things.

Agree and it's in the steel liner of most all aluminum blocks that go south firstEven in the cast in linersThe different rates of thermal expansion and contraction is just oneaspectThe thermal rates of conduction another

BenK wrote:Agree and it's in the steel liner of most all aluminum blocks that go south firstEven in the cast in linersThe different rates of thermal expansion and contraction is just oneaspectThe thermal rates of conduction anotherNot at 200 degrees,high silcon alloy (same as a piston)Biggest problem is packaging , alloy blocks get very big when they are made as strong as needed,thats why CGI is replacing even alloy -they are smaller.

Aluminum Engine Blocks | Good Sam Community

42 Replies

brulaz
Explorer
Jan 13, 2015
jus2shy wrote:

The latest aluminum blocks use a process called Plasma Arc Deposition or Plasma Wire Deposition. Basically, iron is heated up to a plasma and sprayed into an aluminum bore in an aluminum block motor (Ecoboost 3.5 has this I believe). Makes for an extremely hard finish. No steel liners. I don't know if we'll see this tech applied to HD engines, what I see being more of a fad is going to CGI.
...

Yes, I think think the 3.5 EcoB has this. Recall some awesome videos of the process back in 2011 when it first came out.

But now Ford's going to the dual CGI-Al Alloy block in the 2.7 EcoB. Wonder why? Cost? Durability? Just a trendy experiment?

Whatever, looks like there's still a lot of engineering that can go into ICEs.
BenK
Explorer
Jan 13, 2015
Thanks, great info

In one of my past careers...designed inverters to 'sputter' onto silicone wafers
and is similar to what you describe...but for wafers in the 200mm dia range

Wonder how they did it for a much larger area and the speed it 'must' need to
make it economical?
jus2shy
Explorer
Jan 13, 2015
BenK wrote:

Aluminum blocks still needs steel liners that last time I did any
research into AL blocks...and...all of the attendant issues with
dis-similar metals...wet or dry, HOW2 manage it at the head junction, etc, etc, etc

The latest aluminum blocks use a process called Plasma Arc Deposition or Plasma Wire Deposition. Basically, iron is heated up to a plasma and sprayed into an aluminum bore in an aluminum block motor (Ecoboost 3.5 has this I believe). Makes for an extremely hard finish. No steel liners. I don't know if we'll see this tech applied to HD engines, what I see being more of a fad is going to CGI. The issue with aluminum is that you have to fight deflection on larger in-line motors which many HD motors are. With V configured motors, you have more opportunity for girdling the engine with natural structure. Even the Cummins ISB with its grey-iron construction can deflect a bit by hand. I think that's the primary challenge with HD engines. Lots of open space (big pistons) and not as much opportunity to square it up and strengthen it without adding significantly more bulk to an in-line engine.
mooky_stinks
Explorer
Jan 13, 2015
RAS43 wrote:
mooky stinks wrote:
It's a good thing we don't use aluminum transmissions for all that torque! lol
I think we'll see aluminum blocks in HD trucks very soon.

Most transmission housings are aluminum and have been for many years.

I know. That was sarcasm and a joke.
RAS43
Explorer III
Jan 12, 2015
mooky stinks wrote:
It's a good thing we don't use aluminum transmissions for all that torque! lol
I think we'll see aluminum blocks in HD trucks very soon.

Most transmission housings are aluminum and have been for many years.
BenK
Explorer
Jan 12, 2015
Funny you should bring up aluminum rods...

When a teen and a member of the Morgan Club of SF (tech advisor to a bunch of
doctors, lawyers, etc) and think all they really wanted was access to my garage's
welders/engine hoist/tools/etc

Anyway, came across a guy building engines for them and found he was milling out
rods out of aluminum. Just started college and a young upstart...

He found that I knew HOW2 run an end mill, so he put me to work in trade for my
stuff wanted out of his machine shop

Made 4 sets and every set blew up around a million cycles. Crumbled bits of
aluminum. Fatigue failures

His reasoning is that pistons were made out of aluminum and forged the best.
Though there were cast Al pistons too. So since they are connected to one end
of a rod...why not make the rod out of AL...

Boy did those in-line fours zing up the RPM scale...

Aluminum blocks still needs steel liners that last time I did any
research into AL blocks...and...all of the attendant issues with
dis-similar metals...wet or dry, HOW2 manage it at the head junction, etc, etc, etc
Turtle_n_Peeps
Explorer
Jan 12, 2015
jerem0621 wrote:
mooky stinks wrote:
You speak as if aluminum blocks don't and can't possibly exist. They're already in trucks with 12000lb towing capacities. They're not far off from being in HD trucks.

Yep, that's the problem I keep having on this issue.

The 6.2 is in the GM trucks getting used and abused every day. I have not heard of any engine block related failure due to it being aluminum. This is not a new motor...it's been out in the field for many years.

Maybe we need 10 years in the field or better before we see any issues...I am not really sure.

Thanks!

Jeremiah

It's not that you can't make an aluminum block. You can. It's not that you can't make a lot of power out of an aluminum block, you can.
It's just that iron is a much better material to make blocks out of for HD service. Much like, can you make aluminum rods? Sure you can; but there are much better materials to make rods out of for HD service.

Jeremiah when you say " the 6.2 is in the GM trucks getting used and abused every day. I have not heard of any engine block related failure due to it being aluminum"; this is like saying I can put my LBZ duramax in a class 8 truck and it will be fine because after all I haven't heard of any engine failures in pickups. A 1500 pickup and a 3500 pickup are worlds apart in duty cycle just like a class 8 truck is worlds apart from a 3500 pickup in duty cycle.

The fact of the matter is, the LS block is NOT a heavy duty block. (just look at the inside of one) Much like the V6 Ecoboost is not a HD block. That is not what they were designed for. Much like the Duramax was not designed for class 8 duty. That is not what it was designed for.

Bottom line is, are we going to see aluminum blocks in HD pickups? Maybe, (hell, they had aluminum diesel blocks well over 50 years ago)but it won't be the LS block without GM improving it substantially.
jerem0621
Explorer II
Jan 12, 2015
mooky stinks wrote:
You speak as if aluminum blocks don't and can't possibly exist. They're already in trucks with 12000lb towing capacities. They're not far off from being in HD trucks.

Yep, that's the problem I keep having on this issue.

The 6.2 is in the GM trucks getting used and abused every day. I have not heard of any engine block related failure due to it being aluminum. This is not a new motor...it's been out in the field for many years.

Maybe we need 10 years in the field or better before we see any issues...I am not really sure.

Thanks!

Jeremiah
mooky_stinks
Explorer
Jan 12, 2015
You speak as if aluminum blocks don't and can't possibly exist. They're already in trucks with 12000lb towing capacities. They're not far off from being in HD trucks.
Turtle_n_Peeps
Explorer
Jan 12, 2015
BenK wrote:
Transmissions do NOT have fueled burns (almost an explosion), nor does
it have metal assemblies moving in one direction at almost the speed
of sound...to then stop and reverse to go the other way just as fast
several times a second

Nor does it have the temps in it's innards...like +1,000* F

Not a good comparison between an ICE and transmission

Good post Ben, and spot on.

Comparing a tranny to an engine block is ridiculous. Much like comparing an aluminum engine head to an aluminum engine block.

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Aluminum Engine Blocks

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