What's the appeal of an aluminum engine block?

[Blue66]

I call them cool guy parts in the Buick turbo world. Bragging rights Now in the COBRA world I felt better with it because of all the 427s we had in the 60/70s that guys blew up.. Trying to find a really nice cast iron block could be challenging. On the good side less weight on the nose. Really haven't beat on it bad. Still have little V6 Turbo's if I want a hell ride. Plus we have a lot of parts from hoarding

[moore_rb]

Originally Posted by Blue66

I call them cool guy parts in the Buick turbo world. Bragging rights

I'm with this guy...- Most dudes are going to tell you they want aluminum instead of iron for both the reasons you mentioned - Weight, and for the "cool factor"

But my personal opinion is that these 2 reasons mask the real rationale, which is technical ignorance, augmented by a fat checkbook...

"A fool, and his money, are soon parted"
- Benjamin Franklin.

It's the same reason that guys are coming to you asking for a 700hp solid roller, for a car that they put 500 miles a year on, driving around to car shows and parking lot meets.

Bench racing is fun, without being nearly as scary, or time consuming, as the real thing...

[Phx Mike]

Originally Posted by moore_rb

I'm with this guy...- Most dudes are going to tell you they want aluminum instead of iron for both the reasons you mentioned - Weight, and for the "cool factor"

But my personal opinion is that these 2 reasons mask the real rationale, which is technical ignorance, augmented by a fat checkbook...

"A fool, and his money, are soon parted"
- Benjamin Franklin.

It's the same reason that guys are coming to you asking for a 700hp solid roller, for a car that they put 500 miles a year on, driving around to car shows and parking lot meets.

Bench racing is fun, without being nearly as scary, or time consuming, as the real thing...

Not sure why you would say it is technical ignorance. The aluminum block weighs about 60 lbs less than the iron block. That's not insignificant if you care about weight. And if you choose an iron block and aluminum heads you have to consider the thermal expansion differences and what issues that may or may not create. Going with the iron heads adds more weight.

I made a very conscientious decision to choose aluminum for the engine block in my car due to the resale value and because it is in keeping with the "technology" and low weight focus of the Kirkham product design (billet suspension components etc). I don't think that makes me a "fool" or a "bench racer".

There is no question that aluminum sand castings have more porosity issues than cast iron components - this is a problem in the aerospace parts world also and the associated casting yield gets built into the cost of the parts. There are ways to help mitigate it such as hipping, mold and core design, mold heat and pouring technique but none are foolproof nor inexpensive and certainly not approaches that are well suited to low volume production.

It will be interesting to see 3D printed parts when the additive manufacturing machines get large enough to make them.

[blykins]

I know it probably wasn't meant to sound that way, but this is not an engine builder experience issue. I've built more all-aluminum FE's than I can remember right now.

When you get a fresh block out of the box and it doesn't pass a pressure test, there's really not any experience that needs to be involved there....unless it involves going with another block manufacturer. However, there have been issues with all of them at one time or another.

What it comes down to for me is that I'm really not willing to be a guinea pig for new foundries or new block manufacturers, especially when I've had issues in the past. I understand that cast iron blocks are probably cast using the same foundries, but as the others have pointed out, the aluminum blocks have more of a chance for porosity.

[fordracing65]

Originally Posted by Phx Mike

Not sure why you would say it is technical ignorance. The aluminum block weighs about 60 lbs less than the iron block. That's not insignificant if you care about weight. And if you choose an iron block and aluminum heads you have to consider the thermal expansion differences and what issues that may or may not create. Going with the iron heads adds more weight.

I made a very conscientious decision to choose aluminum for the engine block in my car due to the resale value and because it is in keeping with the "technology" and low weight focus of the Kirkham product design (billet suspension components etc). I don't think that makes me a "fool" or a "bench racer".

There is no question that aluminum sand castings have more porosity issues than cast iron components - this is a problem in the aerospace parts world also and the associated casting yield gets built into the cost of the parts. There are ways to help mitigate it such as hipping, mold and core design, mold heat and pouring technique but none are foolproof nor inexpensive and certainly not approaches that are well suited to low volume production.

It will be interesting to see 3D printed parts when the additive manufacturing machines get large enough to make them.

Pond website. Iron fe block 285lbs. Aluminum fe block 135lbs. That's a 150lbs difference. You're about 90lbs off.

[Phx Mike]

Originally Posted by fordracing65

Pond website. Iron fe block 285lbs. Aluminum fe block 135lbs. That's a 150lbs difference. You're about 90lbs off.

It says the weight of the original iron block was 195 lb which is what I was using as a reference.

[undy]

Three words for porosity issues... Vacuum Casting Impregnation. The OEMs use it quite often on their aluminum castings. I used it on my Dove 2x4 Tunnel Wedge intake. Dove pretty much invented casting porosity, lol...

The VCI process is a wondrous thing. The item (block, intake manifold, alloy trans/differential housing etc) is placed in a vacuum chamber and the chamber is drawn down to about 50 microns (29.86" of vacuum or there abouts). The vacuum is then broke with a highly viscous, permeable and hardening fluid. Since every minute and not so minute pour is under vacuum too the fluid fills the voids completely. The fluid after hardening is completely durable and good to any temperature that the aluminum itself could stand. It will last as long as the part does.

On the down side, all machining must be accomplished prior to the process. For a block the process would be around $200. Volume draws down the costs too.

Just a technical tidbit that may or may not be useful.

[patrickt]

Originally Posted by undy

For a block the process would be around $200. Volume draws down the costs too.

OK, so for the price of a good dinner you can virtually eliminate, not just mitigate, the porosity concerns of an aluminum block? Uhhhh, this is starting to sound pretty easy....

[RodKnock]

Originally Posted by undy

Three words for porosity issues... Vacuum Casting Impregnation.

Undy does the "three word" thing too.

He also seems pretty smart to me. He wouldn't trade his Pond alloy for two cast iron BBM's.

Statements (and even solutions) by Barry R:

Originally Posted by Barry_R

Every single aluminum block I do will get impregnated from now on (Bill - your's was done too) after I had an issue a few years ago. The cost is added into the build, but I do not call it out because customer get nervous about a process the might not understand. This place does a bunch of military and OEM transmission stuff.

The weight savings is nice and I can fully understand the desire. The blocks themselves seem to be consistently inconsistent in quality. I have always been able to build them into good engines but they are always a challenge and I kind of agree with the sentiment - they should cost 20% more for labor because of the extra effort required.

The 427 stuff is definitely cool - given the choice I would prefer to build an iron block every time. We pretty much never have any issues with 390 based 445 builds, and we do them at a rate of two or three per month.

I noticed that Barry mentions building and not having many, if any, issues with original cast iron FE blocks, but doesn't mention aftermarket cast iron blocks. Hmmm.

[moore_rb]

Originally Posted by Phx Mike

Not sure why you would say it is technical ignorance. ....

I made a very conscientious decision to choose aluminum for the engine block in my car due to the resale value and because it is in keeping with the "technology" and low weight focus of the Kirkham product design (billet suspension components etc). I don't think that makes me a "fool" or a "bench racer"

I wasn't talking about you... I already knew why you chose an aluminum engine for your car... It fits a theme with your car's overall styling- I get that.

But Brent's original points are very valid- aluminum makes perfect performance sense for cylinder heads... but not engine blocks; unless weight is the most important factor to you (which it clearly must be to many, many guys out there)

- Not knockin, just sayin...

And yes- Until your car has a time slip from a drag strip, or a road course (or has generated a fist full of cash from an illegal Saturday night out on some road in boonies, sorry to say- You're a bench-racer.

But that's ok- I'm a bench racer, too... My best days throwing a car around a track are probably behind me... I can tell whenever I get a little punchy in my Cobra that my eyesight and my reflexes aren't what they were 15 years ago....

And I never said bench-racing wasn't fun

[fordracing65]

Originally Posted by moore_rb

I wasn't talking about you... I already knew why you chose an aluminum engine for your car... It fits a theme with your car's overall styling- I get that.

But Brent's original points are very valid- aluminum makes perfect performance sense for cylinder heads... but not engine blocks; unless weight is the most important factor to you (which it clearly must be to many, many guys out there)

- Not knockin, just sayin...

And yes- Until your car has a time slip from a drag strip, or a road course (or has generated a fist full of cash from an illegal Saturday night out on some road in boonies, sorry to say- You're a bench-racer.

But that's ok- I'm a bench racer, too... My best days throwing a car around a track are probably behind me... I can tell whenever I get a little punchy in my Cobra that my eyesight and my reflexes aren't what they were 15 years ago....

And I never said bench-racing wasn't fun

Not true. Brent does not like FE blocks because of the consistency in casting them. Every other aluminum block is fine. OEM blocks go over 100,000 miles easy with no problems. 90 percent of daily drivers use them. It's the quality of the FE blocks.

[fordracing65]

If there was a market for FE stuff the blocks would be fine because they would be sold in such high quantity they would be able the get someone to do it right. But with the cost to do that and such low FE interest nobody will. Or so it seems.

[moore_rb]

Originally Posted by moore_rb

But Brent's original points are very valid- aluminum makes perfect performance sense for cylinder heads... but not engine blocks; unless weight is the most important factor to you

Originally Posted by fordracing65

Not true. Brent does not like FE blocks because of the consistency in casting them. Every other aluminum block is fine. OEM blocks go over 100,000 miles easy with no problems. 90 percent of daily drivers use them. It's the quality of the FE blocks.

I agree- This thread was started to discuss casting issues with FE blocks specifically.

However- to your statement about "every other" OEM block being just fine in aluminum; well, I also agree- They are "just fine" in OEM applications... But they are not better than iron for high cylinder pressure/high torque applications.... None of them.

So, nothing I originally stated was "not true"

Example: the 2017 Corvette Z06. Comes with 650HP from an all aluminum engine, whose design has been rigorously tested to go 100k+ miles. It runs about 10.5psi of boost from the factory.

BUT- The moment you take that same Corvette to Lingenfelter Engineering, and say "I want to make 1500+HP" The first thing Lingenfelter is going to do, is try to talk you into upgrading to one of their iron truck blocks, before they even start adding boost.

I stand by what I stated: From a strength and durability standpoint, aluminum is not superior to iron for any high pressure/high performance engine block. Aluminum's only advantage is weight...


EDIT: WAIT! - I am calling BS on myself - There is indeed another advantage (besides weight) to aluminum, versus iron: Repairability- a cracked aluminum block can usually (but maybe not always) be welded, re-machined, re-sleeved, and re-used, while a cracked iron block is junk 99% of the time.