What's the appeal of an aluminum engine block?

[olddog]

I think the issues you have with aluminum FE engines is partly the size. The bigger the part the more thermal expansion you have to deal with. In the case of aluminum, bigger is not better. On a cold day you have almost zero clearance in your bearings.

Secondly you are dealing with a replaceable sleeve design. Go talk to the diesel builders and see what they have to say. I don't think they are begging for aluminum blocks. They do deal with sleeves moving, and they know some things.

I read many years ago how Ford was casting the sleeves into the 4.6 modular blocks. The outer surface of the sleeve is knurled or grooved and the molten aluminum is cast around them. There is no way for the sleeve to move it is trapped. It makes replacing them difficult. You have to bore it out until the wall is paper thin. Then bend it until it comes out. Certainly design plays a roll.

One of the properties of aluminum is that when a force is applied to it, it slowly creeps over time. That is why you torque lugs down on aluminum wire once. It would tighten more, if you re-torqued them yearly. Eventually you would pinch the wire off. There are hug differences in different grades of aluminum. I'm not certain that the people who are designing aluminum blocks are choosing the right grade for the design.

I have been told porosity in aluminum has to do with humidity. It cannot be cast with humidity above a certain amount. GM had problems with porosity in the Cadillac north star for years. If GM fought it, it isn't simple to do.

I think aluminum and replaceable sleeves on a large engine is challenging to do right.

You might want to talk with Barry, Craft, and some of the other builders. Together all of you may be able to impact what the block manufactures are doing. The solution to your problem is at the manufacturers. It is not uncommon for users of a product to partner with the supplier to resolve issues. When all the players have a seat at the table, better decisions are are usually made.

[Dominik]

In the 90s I used a (old!) Chevy 4.44" block in my car. PITA... Granted, it was old and showed weaknesses. I would never offer such engine for a customer, unless you want to get married to him.

As for the weight "in the front", most Cobras have a weight distribution of 50/50. When I replaced the alu motor with a a cast iron one, I had to drop the front and rear suspension equally.

The ally blcok cools better. Probably too good for street use, even on German Autobahn.

A 454 cui Small Block with aluminium heads would be a sensible compromise. Or, for FE look a 390 stroker.