What's the appeal of an aluminum engine block?

[blykins]

I've always wondered why a lot of my customers requested aluminum blocks for their FE builds. I have asked one or two of my patrons the reasons for their choice and the answers usually revolved around weight.

Is that the most common reason?

Or is just the exotic-ness (is that a word?) of having an "all-aluminum engine"?

Here's my side of it....

At the quantity level that aftermarket FE blocks are manufactured, the quality will always be a variable. If the blocks were made by a big name manufacturer, such as Ford Racing, Dart, World Products, etc., where the quality could be nailed down, it may be a different story.

Now, I will say that the manufacturers that I work with are top notch on customer service and will usually fix or reimburse for any problems that come up. However, the downtime and hassle simply aggravate me.

I've never had an issue with any aftermarket cast iron block but I've experienced quite a few casting flaws on aluminum blocks that would have induced severe internal water leaks if they had not been discovered before-hand. These are usually caught on a pressure test before machine work begins but will still set a build back by a few weeks at the least.

The sleeves can also cause issues. It is nice to have a block that can essentially have the cylinders replaced at will, but it does make for a hairy situation at the beginning as all the sleeves have to be set. This involves the use of an oven and a torque plate to push the sleeves down as far as they will go, so they will not drop when the assembled engine is running and has heat in it.

Aluminum blocks just don't make the same horsepower that a cast iron block will make with an equivilent build. The blocks expand, move around, etc., which can reduce ring seal and the amount of power that's made. Due to the expansion rate of aluminum, main bearing clearances have to be adjusted while assembling, to allow for the clearances opening up under operating temperature.

On the positive side of things, the aluminum blocks are lighter. However, this doesn't really mean much for the average Cobra owner. If you are racing, this may be a concern, but for the regular street car build, I personally see no benefit.

So, the motive behind my long-winded post was actually two-fold. The first motive was just to poll the Club Cobra crowd to see what the consumer level of thinking was behind the aluminum blocks. The second motive was just to vent a little bit. I have made the decision to not accept any more all-aluminum FE build orders. Not sure if I will retract that decision later on down the road, but to me, the pros just don't outweigh the cons and if an issue occurs on a build, the builder is always the one to incur the cost.

As some of you know, aftermarket FE blocks have been non-existent this year. I've been waiting on blocks since February and still have not received any. Foundries have changed, designs have changed, and until things settle down, I just have to go with my gut.