I just ran across this discussion and wanted to say that I have not had anymore problems with aluminum blocks than I have had with cast iron blocks. About the only time I get contacted is when someone has a problem. The only real problem we have had with any of the FE engines is the deal with the Fel-Pro intake gaskets. We have worked with Cometic and Eldebrock to get a better gasket that fits the ports better and will hold up to the new anti-freezes as well as some of the minerals in the water. I can say that 10 years ago we never had this problem but who knows what may have changed with the anti-freeze and or the gaskets.
As far having any problems with the blocks I have not had anyone call with any. I do not know how many miles some of the guys may have on them. We have several that have been out there for at leat five years now. If the block is checked properly and machined right I do not think there should be any real problems.
We have had a few problems with some of the rear main seals but we do not make the blocks or the cranks. We have gotten them to put the grooves in the cranks to help direct the
oil back into the engine and away from the rear seal in the last year as well as doing a special double seal set up to try and help this problem.
As with any cast part there can be flaws, cast iron or aluminum so we have seen a few of the blocks with pirosity problems from time to time but we normally catch this with the pressure test that we do. I agree with what was said before about the heat cycle issue being more important than actual miles. If a part is heated to its max or close to it time and time again in a short period of time it will lose some of its strength. We see this with some of the dirt track late model engines we do. They get them up to 230-250 sometimes as well as turning them 9000 rpms and this does hurt the life of the block. With normal use in a Cobra I see no problem getting 100,000 miles out of one if that is what it was built to do. I can see the engines we build out living a lot of the other parts on the car. I will also add this, most of the engines we sell do not get driven like a daily driver car either and we all know that.
Thanks, Keith Craft