What's the appeal of an aluminum engine block?

[RodKnock]

Originally Posted by blykins

We're not driving Porsches.

And you're likely not driving Toyota's, Subaru's, Miatas, RX-7's, Corvette's, BMW's, etc. either, but the "hot rod" consumer desires lightweight parts.

Since the dawn of time, tennis rackets, baseball bats, wiffle balls, engine blocks, have become lighter. Why? To go faster, hit the ball farther, etc.

One word. Plastics.

[undy]

Brent, I'm assuming the only reason you're seeing increased HP is due to cast iron's increased thermal retention? Once aluminum heats up and comes up to "designed clearances" ring sealing should be the same as cast iron. Blow-by and effective static or dynamic compression ratios should also be the same as iron. My training leads me to think that the horsepower differences should be minimal. Thoughts?? Just curious...

[RodKnock]

Originally Posted by undy

Brent, I'm assuming the only reason you're seeing increased HP is due to cast iron's increased thermal retention? Once aluminum heats up and comes up to "designed clearances" ring sealing should be the same as cast iron. Blow-by and effective static or dynamic compression ratios should also be the same as iron. My training leads me to think that the horsepower differences should be minimal. Thoughts?? Just curious...

^^^I like what Undy said. He knows what he's talking about.

[undy]

Originally Posted by RodKnock

^^^I like what Undy said. He knows what he's talking about.

In the case here it would seem that the position dictates the argument, not the argument dictates the position.

BTW... I wouldn't trade my alloy pond 482 for 2 cast iron 482s.

[blykins]

My guess is that an aluminum body is exactly like an original.

"I" would drop a cast iron block into a CSX or Kirkham, because I like repop stuff.....not resto-mod stuff.

Let me ask you, Rod......why do you think all the engine builders want a cast iron block?

Undy,

Aluminum blocks expand. They squirm. They distort. You lose ring seal. Remember, you GAIN .014-.015" of valve lash (or lose that much preload on a hydraulic cam) on an all-aluminum engine between cold and hot. Think about how much things are moving around.

I think all that's worth saying has already been said and this isn't going to turn into a small block/big block thread on my account. So, I'll see you all on the other side.

[RodKnock]

Originally Posted by blykins

Let me ask you, Rod......why do you think all the engine builders want a cast iron block?

"All." Another global statement. You're speaking for every engine builder in the US or the world? I don't recall Tom Lucas steering me away from aluminum and pitching me feverishly to buy a cast iron block.

Brent, it's OK. We understand your position after 12 pages. You're not building anymore engines with aluminum blocks (or until business slows down).

[1ntCobra]

Originally Posted by blykins

My guess is that an aluminum body is exactly like an original.

"I" would drop a cast iron block into a CSX or Kirkham, because I like repop stuff.....not resto-mod stuff.

When I first joined this site I thought that getting a Cobra most like an original would be the thing to do. But after being around for a few years I changed my mind. Sure a cast iron block in an alloy CSX would be nice if the CSX has an original style suspension, but apparently alloy CSX cars now come standard with Kirkham billet suspensions, hmm. Now the thought of a Kirkham with billet aluminum parts being lighter than an original CSX has me thinking why wouldn't you want to have a nice light aluminum block FE to make the car that much more lighter? Building the lightest Kirkham possible sounds like a cool thing to do, even if it means that Brent will not be the person building the engine.

[RodKnock]

Originally Posted by 1ntCobra

Building the lightest Kirkham possible sounds like a cool thing to do, even if it means that Brent will not be the person building the engine.

Yes! My feeling exactly.

[blykins]

Forgot to add....aluminum blocked engines lose compression when they get hot. Stuff grows. A lot.

[undy]

So... I get that it's a costly and risky to build an alloy FE. I agree with that, but what I differ on is the increased HP. Yes, I hear that it "moves around a lot", concur there too. But... that's on warm-up. Once things warm up to design temperature, if it was built correctly, the bearing clearances, piston to cylinder clearances, ring gaps & lifter clearances/preloads etc get where they're supposed to be. Unless you run a cold engine the HP levels should be very close to being equal. I've heard no explanation thus for proving otherwise.

All alloy engines, OEM inclusive, would be subject to this. It just isn't so...

EDIT: just saw Brent's post. I guess we'll have to agree to disagree here. It's really a moot point considering the intent of the original post.

[blykins]

That's fine Dave, it's an accepted fact by engine builders that doesn't need to be argued here.

Under higher horsepower conditions, you will lose power with an aluminum block due to cylinder distortion, loss of ring seal, and a decrease of compression. This isn't an operating temperature issue but just a strength issue. I have torn down all-aluminum FE builds where the block was honed with torque plates, but the sleeves still had "shadows" from where the cylinders distorted. I suppose you could "hot hone" the blocks, but there again......why put the effort into it?

To be fair, yes, you can "design in" more compression ratio, but you still have to deal with the squirming around of the blocks. Bearing clearances are something that the engine builder has to set ahead of time, along with running the valves to make sure everything is kosher when it's hot.

I looked at my dyno sheets. I don't have any *exact* combinations where the only difference is the block material. Maybe Barry might have something like that. I think I've talked to Barry about this before (engine builders do talk to each other, BTW) and he said with his career at Federal Mogul, he rubbed elbows with a lot of the race teams....the general consensus was that iron blocks made more power.

Maybe he'll chime in....

[patrickt]

Brent, I think you should be paid for putting up with all this crap....

[RodKnock]

Originally Posted by blykins

That's fine Dave, it's an accepted fact by engine builders that doesn't need to be argued here.

More global statements, speaking for all engine builders. And it can't be argued?

You're making the Pond and Shelby blocks sound like Pepsi/Coke cans. People use aluminum pistons, rods, cylinder heads, intakes, rocker arms, etc. Until I see at least a good statistical sample of equally built FE engines, built with both cast iron and aluminum blocks, I call BS.

I know we live in a "post truth" or "truthiness" society now, but I need factual data sampling. And you line up 10 engine builders to post here on this thread that agree with you, but it's all hot air until I see real DATA!

It says right on the Shelby website:

"Strong enough to support over 1500 horsepower outputs."

"Shelby's FE alloy block delivers superior bottom end stability at high rpm."

[blykins]

I have trouble discerning between the guys who ultimately want to know/learn and the guys who just like to stir the pot.

[patrickt]

Originally Posted by blykins

I have trouble discerning between the guys who ultimately want to know/learn and the guys who just like to stir the pot.

That's because we swap hats on the fly....

[blykins]

Ok, some data I found from the FE forum since I don't have any dyno sheets to prove my point.

From Dave Shoe (speaking to Robert Pond):

"The horsepower differences between iron nand aluminum blocks have been repeatedly characterized by Robert Pond, though I am necessarily distorting his claims because I lack sufficient experience to fully comprehend all his findings. He has been particularly interested in horsepower gains as small as a single horsepower, as his Stock Eliminator racing engines are constrained in the modifications which are allowed. I've spoken to Robert a little bit about "free horsepower", and he strongly contends that the block, all by itself, can provide dozens of free horsepower between the 600 to 1000 horsepower levels, just by its cylinder rigidity characteristics."

From Barry R, speaking of his Federal Mogul days:

"Well - - I can add a little fuel to the fire.
I supply rings and bearings to a large percentage of Pro Stock, Cup, and fastest street car competitors. In virtually 100% of situations where the weight is not critical (meaning that they would have to add ballast to offset any weight benefit from aluminum to meet a mandated minimum) these competitors ALL run an iron block of some sort.

Iron blocks simply make more power. Every time. The commonly bandied about number is somewhere between 15 and 30 - depending on the power level and the particular engine in question. Big beefy billet caps on aluminum blocks are kinda like a super strong steel lid on a cardboard box - when they're stronger than the parent material the value is limited. Ultimate power handling potential is not an issue - both materials have been proven at levels beyond anything feasable in an FE (I have seen numbers near 3000HP).

When properly prepped and designed, neither material will show bearing issues - but aluminum does require tighter cold clearances. Fuel motors don't count - - repairability is more important than the nominal power difference when you're at that level. The sole benefits to an aluminum block are identical to those of aluminum heads - weight ease of modification and repairability."

[RodKnock]

Originally Posted by blykins

Ok, some data I found from the FE forum since I don't have any dyno sheets to prove my point.

From Dave Shoe (speaking to Robert Pond):

"The horsepower differences between iron nand aluminum blocks have been repeatedly characterized by Robert Pond, though I am necessarily distorting his claims because I lack sufficient experience to fully comprehend all his findings. He has been particularly interested in horsepower gains as small as a single horsepower, as his Stock Eliminator racing engines are constrained in the modifications which are allowed. I've spoken to Robert a little bit about "free horsepower", and he strongly contends that the block, all by itself, can provide dozens of free horsepower between the 600 to 1000 horsepower levels, just by its cylinder rigidity characteristics."

From Barry R, speaking of his Federal Mogul days:

"Well - - I can add a little fuel to the fire.
I supply rings and bearings to a large percentage of Pro Stock, Cup, and fastest street car competitors. In virtually 100% of situations where the weight is not critical (meaning that they would have to add ballast to offset any weight benefit from aluminum to meet a mandated minimum) these competitors ALL run an iron block of some sort.

Iron blocks simply make more power. Every time. The commonly bandied about number is somewhere between 15 and 30 - depending on the power level and the particular engine in question. Big beefy billet caps on aluminum blocks are kinda like a super strong steel lid on a cardboard box - when they're stronger than the parent material the value is limited. Ultimate power handling potential is not an issue - both materials have been proven at levels beyond anything feasable in an FE (I have seen numbers near 3000HP).

When properly prepped and designed, neither material will show bearing issues - but aluminum does require tighter cold clearances. Fuel motors don't count - - repairability is more important than the nominal power difference when you're at that level. The sole benefits to an aluminum block are identical to those of aluminum heads - weight ease of modification and repairability."

Data please! A good statistical sampling too.

All this BS for "dozens of HP" or "15-30 HP"? Oy vey. OMG!

I'd say lose 25 lbs of fat and stop eating the Havarti cheese, unless it's my favorite, cottage. And see what kind of 1/4 mile times folks can do.

[blykins]

Happy Thanksgiving all....I'm taking a few days vacation.

[patrickt]

Originally Posted by blykins

Happy Thanksgiving all....I'm taking a few days vacation.

Well, that was a definitive posting. Just pm your login password and I'll keep posting in your stead, and piss them off way better than you ever could....

[undy]

Thanks for the detailed explanation Brent. I understand now.

It would seem that ALL FE aluminum blocks suffer from inherent structural design deficiencies. Other alloy OEM blocks (not sure about aftermarket) don't suffer from this at all.

I pulled my heads on my 88K mile LS7 (Z06) engine and the ring sealing/pattern was perfect. That was at elevated HP levels too. It has zero oil consumption and very little, if any, blow-by.