Iron cast block VS alu block
Race Director
Joined: Jan 2005
Posts: 10,641
Likes: 13
From: Slidell Louisiana
I don't see how the block material would change rpm potential of a street driven SBC based engine.
Valve train and rotating assembly would have bigger impact on the ability to survive higher rpms.
Valve train and rotating assembly would have bigger impact on the ability to survive higher rpms.
Thread Starter
Drifting
Joined: Sep 2014
Posts: 1,579
Likes: 59
From: Trieste Italy
Ok so which are pros and cons about them? Maybe alu weight advantage or better iron cast thermal conductivity
Last edited by Christi@n; Aug 30, 2015 at 03:05 PM.
Le Mans Master
Joined: Oct 1999
Posts: 6,366
Likes: 34
Assuming this is Gen 1 vs Gen 1 SBC.
Aluminum block is lighter. I think it was 40 to 50 pounds lighter then a gen 1 iron block.
It also costs something like $5000.00 US for just the block.
You have to sleeve the cylinders. which is a plus or minus depending on what you do with it. For a street car, not worth it. All out effort race car... Meh!
I don't remember if the lifter bores need to be sleeved as well.
Aluminum is not as strong as cast iron. If you have a rod failure, you can bet the block will end up trash with a hole in it. Just like some of the Lsx engines do.
For this comparison alone, it makes putting an LSx series engine in the car all that much better economically . you can get a whole LS3 for $7K and it will be lighter and better then Gen 1 decent race stuff. The LS6 crate engine which has been discontinued it seems was $5500
Thermally it will heat up at the same rate as aluminum heads. Compared to say aluminum heads on an iron block.
That is about all I can think of.
It will have no other performance impact.
If you need to lift the bare block, it will be something like 90-100 pounds, compared to what I weighed my bare l98 block at 145 pounds.
Aluminum block is lighter. I think it was 40 to 50 pounds lighter then a gen 1 iron block.
It also costs something like $5000.00 US for just the block.
You have to sleeve the cylinders. which is a plus or minus depending on what you do with it. For a street car, not worth it. All out effort race car... Meh!
I don't remember if the lifter bores need to be sleeved as well.
Aluminum is not as strong as cast iron. If you have a rod failure, you can bet the block will end up trash with a hole in it. Just like some of the Lsx engines do.
For this comparison alone, it makes putting an LSx series engine in the car all that much better economically . you can get a whole LS3 for $7K and it will be lighter and better then Gen 1 decent race stuff. The LS6 crate engine which has been discontinued it seems was $5500
Thermally it will heat up at the same rate as aluminum heads. Compared to say aluminum heads on an iron block.
That is about all I can think of.
It will have no other performance impact.
If you need to lift the bare block, it will be something like 90-100 pounds, compared to what I weighed my bare l98 block at 145 pounds.
Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 196
From: folsom california
modern gasket technology has overcome this to a great extent but iron and aluminum expand and contract at different rates and aluminum heads on an aluminum block would theoretically offer better sealing;
assuming something less than a catastrophic failure, aluminum is repairable; cast iron, not so much.
an aftermarket cast iron block is gonna cost more than an OEM cast iron block but will be stronger and offer much improved oiling over OEM but won't be terribly more expensive (maybe even less) than a fully prepped OEM block which still won't be as strong as an aftermarket block ... with strength comes weight... only a few pounds more than an OEM cast iron block
an after market aluminum block? much lighter and crazy expensive ... but if you can afford it, why not?
assuming something less than a catastrophic failure, aluminum is repairable; cast iron, not so much.
an aftermarket cast iron block is gonna cost more than an OEM cast iron block but will be stronger and offer much improved oiling over OEM but won't be terribly more expensive (maybe even less) than a fully prepped OEM block which still won't be as strong as an aftermarket block ... with strength comes weight... only a few pounds more than an OEM cast iron block
an after market aluminum block? much lighter and crazy expensive ... but if you can afford it, why not?
Melting Slicks
Joined: May 2013
Posts: 2,692
Likes: 349
From: Sacramento California
Other thermal properties... an aluminum block will warm up and cool down faster than an iron block. Iron blocks typically retain heat much longer. My LT1 (iron block/alum heads) is still warm to the touch after sitting overnight... at least during the summer.
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Thread Starter
Drifting
Joined: Sep 2014
Posts: 1,579
Likes: 59
From: Trieste Italy
Most likely this property (retain het much longer) is prefereable think
Melting Slicks
Joined: Mar 2002
Posts: 3,108
Likes: 126
From: S.L.C. UT
If your willing to spend the money it takes to buy an aluminum block, I would consider a Dart iron eagle tall deck. Then you can run 461, 464, 468 or 472 cubic inches with a 4.25 stroke. You would still have the weight of a iron block, but the added cubic inches would have the potential if done right to make some pretty big power.
Drifting
Joined: Jul 2009
Posts: 1,258
Likes: 98
From: Ashland PA
2021 C4 of the Year - Modified Finalist
Heres a aluminum block over in the parts for sale section, needs work.
https://www.corvetteforum.com/forums...n-1-block.html
https://www.corvetteforum.com/forums...n-1-block.html
Burning Brakes
Joined: Sep 2005
Posts: 993
Likes: 3
From: Iowa
The main thing with the aluminum block is the ability to repair it. Unless you blow out the lifter bores you can repair virtually anything else. Most don't care to repair a crack in the mains but it has been done plenty of times. Outside of that, most other options can now be had on a cast iron or better yet, a CG block. Just my .02