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Old 10-20-2004, 01:19 PM
firestone's Avatar
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downsides to aluminum blocks

Does anyone know if there are any downsides to running an aluminum block besides the price? I am looking at a 604 with a donovan aluminum block, and I want to know what I am getting myself into.

Thanks,
Adam

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Old 10-20-2004, 01:28 PM
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A magnet won't stick to it. That's about all.
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Old 10-20-2004, 01:50 PM
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It may depend on what you plan on doing with the motor. You didnt say what your using it for or if your buying a new motor or used but some of the race aluminum blocks are made for race only, in that they have odd deck heights or offset lifter bores, this may be something you want to check into first.
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Old 10-20-2004, 02:40 PM
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I'll look into those things.

Thanks for the replys
Adam
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Old 10-20-2004, 02:42 PM
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nowadays?

Cost.

K
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Old 10-20-2004, 02:50 PM
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I know the old aluminum 427 chevy's had problems with freeze plugs, but I don't think thats an issue with any aluminum blocks anymore. I'm not positive though.
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Old 10-20-2004, 05:00 PM
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Check mains, be sure the threads will hold torque.

HP wise an aluminum block will make less then an iron block in the same application. . .sleeve movement = bad ring seal.

As Brainsboy listed, sometime take very special stuff, If it is a 700 block, special oil pan

Other then that, stick a rod throw it, jam a new sleeve in it, weld some plate on it and go again.

Chris
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Old 10-20-2004, 05:26 PM
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Do you have any idea as far as a percentage estimate how much power would be lost using a aluminum block? Is it substantial enough to the point that the amount of lost hp outweighs the fact that you are loosing weight because it is aluminum?

Thanks
Adam
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Old 10-20-2004, 05:54 PM
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Iron SBC = 490 pounds
Aluminium SBC = 75 pounds

The HP loss offset isnt that big of a difference.
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Old 10-20-2004, 05:56 PM
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There is absolutely no down side to an al block...unless you count in that you need some different education in them.
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Old 10-20-2004, 06:26 PM
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Some aluminum blocks don't come with provisions for wet sump oil system and you would have to use a dry sump (not that's a bad thing).
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Old 10-21-2004, 08:02 AM
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Some of the racers I've talked to said there are sealing issues with the tin.








427 Round II
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Old 10-21-2004, 08:22 AM
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Flex, Like Cstraub said. Not just with moving cylinders either.

I helped disassemble an engine built with a Donovan aluminum block. We left the camshaft in place as we removed the crank and discovered that we couldn't get the camshaft out. We had to replace the main caps and retorque them to get the camshaft out. It wouldn't move at all with the caps off.

If an engine was designed with aluminum as the metal for casting then it's all groovy. You have to keep in ming that the SBC was designed to be a 265" engine and made with cast iron. Change that metal and remove a bunch of it to make room for huge crankshafts and pistons=interesting design problems.

The engine ran fine before and after the rebuild. Makes a ton of power too. I just freaked out about the amount of built in distortion to make it work. It must have been a nightmare to machine properly.

Larry
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Old 10-21-2004, 09:52 AM
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Quote:
race aluminum blocks are made for race only, in that they have odd deck heights or offset lifter bores
\

Only because the manufacturer produces them from specific applications. Not because they are a inferior block in any way. They assume someone who spends $3.5k will know what they want. You can buy then all day long with standard small chevy dimensions. Let's not forget that a block costing 3.5k is a long way from a typical small chevy. They are engines built by specs and not by some version of what GM made in 55'.

Quote:
Check mains, be sure the threads will hold torque.
Never a bad idea in any kind of engine. Steel insert are a must in my opinion. The Rodeck block seems to have a main web cracking problem when making 750 or more and the Chevrolet factory aluminum blocks don't have enough thread length in the head stud or main stud area and the mains are weak. Those blocks should be avoided unless its a low power application under 400 horse and 6000rpm

Quote:
HP wise an aluminum block will make less then an iron block in the same application. . .sleeve movement = bad ring seal.
I've never heard or seen this before. Respectively have to disagree. I also assume we are using a good block. Dart, Rodeck SB2.2 or Bowtie or Vinney...ect. It's where most of my experience revolves around. I could be wrong outside this realm

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There is absolutely no down side to an al block...unless you count in that you need some different education in them.
I concur Doctor.

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Some of the racers I've talked to said there are sealing issues with the tin.
Who would spend that much money on a block and put crappy stamped tin foil on it?
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Old 10-21-2004, 11:33 AM
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Quote:
Originally posted by johnsongrass1
\

The Rodeck block seems to have a main web cracking problem when making 400 horse and 6000rpm I've never heard or seen this before. Respectively have to disagree. It's where most of my experience revolves around. I could be wrong outside this realm



I concur

Wow only 400hp??? and 6000rpm... Hard to believe this ....

I dont concur....



I just thought I would do what you did to my quote, I left out about 50% of what you said and pick 1/2 sentences to make a point that had nothing to do with what you said.

I never said race Aluminum blocks are made for race only, I said SOME ARE, and if he is going to buy a used block this should be somthing to check into.
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