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  #1  
Old Mar 20th, 09, 2:20 AM
Stokerboats Stokerboats is offline
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Default Aluminum Block vs Iron Block

Ok, here's the question. Using an Aluminum block with a 4.6" Bore in a street strip car takes off 100 lbs right off the front of the car. Of course there are stories about how Aluminum blocks don't make the power of an Iron block for a variety of suggested reasons but the choice is a Dart Big M which is much heavier than a chevy block therefore adding extra weight in an already over biased front/rear weight. In this kind of scenario how detrimental would the aluminum block really be in the overall picture not counting the cost, and the rest of the build being equal? Or would the lost weight in fact work out in the favor of performance gains?
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  #2  
Old Mar 20th, 09, 2:56 AM
Bomber '67 Bomber '67 is offline
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Default Re: Aluminum Block vs Iron Block

Dan,

This is one of those great debates for which there are many probable outcomes - none of which are 100% winable. What fascinates me is the parallel universe of thought: some say that removing 100 lbs off the car via an aluminum block vs. a Dart Big M is not *worth* the power loss of an aluminum block - yet some guys swear that moving their 43 lb battery to the trunk made a noticable performance improvement. Still others top that by planting a second 43 lb battery in the trunk.

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  #3  
Old Mar 20th, 09, 8:12 AM
bracketchev1221 bracketchev1221 is online now
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Default Re: Aluminum Block vs Iron Block

I can't really say. Mine was a steel block, steel head combo and I switched to an aluminum head, steel Merlin block and pretty much broke even on weight. But if it was me, in my car even if the rule of 100 lbs/ .1 ET change is true, I don't think the cost increase is worth it. That is also considering that you make equal power from one to the other.
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  #4  
Old Mar 20th, 09, 10:24 AM
69 Ratt Vette 69 Ratt Vette is offline
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Default Re: Aluminum Block vs Iron Block

Whose car are we talking about ?

Lighter is always better, if you have to add a little wieght where you need it to even out the balance, you are still ahead of the game by running an aluminum block.

Aluminum blocks are also repairable..
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  #5  
Old Mar 20th, 09, 11:18 AM
cstraub cstraub is offline
 
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Default Re: Aluminum Block vs Iron Block

With an aluminum block with iron sleves you have differences of metal so when temperature is introduced to the equation then you have different expansion and contraction rates. Aluminum blocks loose power because of loosing ring seal due to this law of physics.

Will it affect you. Depends on the power you are looking to make, the build of the engine. I know in NA classes where a 600 CID engine on alky may be used and they are making over 1000 HP engine builders talk of loosing 40HP, but if one these sticks a rod through the cylinder they don't have $5000 prepped boat anchor.
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  #6  
Old Mar 20th, 09, 1:07 PM
CDN SS CDN SS is offline
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Default Re: Aluminum Block vs Iron Block

Quote:
Originally Posted by cstraub View Post
With an aluminum block with iron sleves you have differences of metal so when temperature is introduced to the equation then you have different expansion and contraction rates. Aluminum blocks loose power because of loosing ring seal due to this law of physics.

Will it affect you. Depends on the power you are looking to make, the build of the engine. I know in NA classes where a 600 CID engine on alky may be used and they are making over 1000 HP engine builders talk of loosing 40HP, but if one these sticks a rod through the cylinder they don't have $5000 prepped boat anchor.

So Chris If I understand correctly what your saying at the NA 600-750 hp 500-600ci level on gasoline the HP loss is not as dramatic and the weight may then be a positive factor ....
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  #7  
Old Mar 20th, 09, 1:20 PM
Busted Knuckles Busted Knuckles is offline
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Default Re: Aluminum Block vs Iron Block

Quote:
Originally Posted by 69 Ratt Vette View Post
Aluminum blocks are also repairable..
Sometimes they are, but a busted rod sometimes saws 'em in half. If the pain rail is busted, it's scrap. They're much more often scrap after a blowup than an aluminum head is.
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  #8  
Old Mar 20th, 09, 1:38 PM
cstraub cstraub is offline
 
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Default Re: Aluminum Block vs Iron Block

Quote:
Originally Posted by CDN SS View Post
So Chris If I understand correctly what your saying at the NA 600-750 hp 500-600ci level on gasoline the HP loss is not as dramatic and the weight may then be a positive factor ....
Correct. A high compression high HP engine is going to make more heat. . .more heat more expansion and more movement.
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  #9  
Old Mar 20th, 09, 11:25 PM
Slowpoke70 Slowpoke70 is offline
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Default Re: Aluminum Block vs Iron Block

Not long ago I read about an engine shop that was boring/honing the blocks at operating temperature instead of room temp. I'd think that if any set up would benefit from this, it would be aluminum blocks with steel liners wouldn't it?
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  #10  
Old Mar 21st, 09, 7:13 AM
DragRacer DragRacer is offline
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Default Re: Aluminum Block vs Iron Block

I don't have any data to back this up, but ......

In the past it was pretty common to lose 40-50 HP when switching from an iron block to an aluminum block on a race motor.

Tracy Dennis at Sunset Racecraft has stated that with today's new HD Brodix cast AL blocks or other CNC billet blocks, in most cases the HP lost using an aluminum block is next to none based on back to back testing.
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  #11  
Old Mar 21st, 09, 2:05 PM
Bomber '67 Bomber '67 is offline
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Default Re: Aluminum Block vs Iron Block

Jason, I've wondered how the newer aluminum blocks performed vs. popular legend. I had noticed that Chevrolet rated its ZL1 block for a lower level of max horsepower than the iron block , so I figured that it was the old design of the ZL1 block that was hurting it rather than aluminum being the issue.

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  #12  
Old Mar 21st, 09, 2:13 PM
Xtreme70SS396 Xtreme70SS396 is offline
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Default Re: Aluminum Block vs Iron Block

Interesting thread.

I doubt it's a fair comparison to look at a structurally superior block like a Dart Aluminum compared to a stock cast iron - you may lose HP, but the Dart block is a better block for a variety of reasons. I think the win vs lose scenario depends entirely on how you intend to use it.
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  #13  
Old Mar 21st, 09, 2:48 PM
Tokyo Torquer Tokyo Torquer is offline
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Default Re: Aluminum Block vs Iron Block

Like Chris said.. you hear about the issues with rings seal as well as what it does to lash on your valve train. More thermal expansion issues and a chance for parts to not get along during that expansion.. binding parts, leaks, clearances, etc. I know I couple of guys that run an aluminum block SBC and they say more trouble than it is worth. The idea of loosing all that weight sounds great though. I think they are great for an LS motor that GM or one that Japan puts togther and worked out the bugs, but may be a hassle for the little guy where the adantages do not outweigh the headaches.

mike
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  #14  
Old Mar 21st, 09, 8:30 PM
Stokerboats Stokerboats is offline
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Default Re: Aluminum Block vs Iron Block

Quote:
Originally Posted by bracketchev1221 View Post
I can't really say. Mine was a steel block, steel head combo and I switched to an aluminum head, steel Merlin block and pretty much broke even on weight. But if it was me, in my car even if the rule of 100 lbs/ .1 ET change is true, I don't think the cost increase is worth it. That is also considering that you make equal power from one to the other.
Perhaps I should have mentioned that we're increasing bore size by a bunch so the weight is not the only benefit.
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