OK OK OK. In the one sentence I said all and should have used MOST. HAPPY now! YES there are SOME aftermarket blocks that use aluminum. Clearly I should get out more often. Clearly I have much to learn. THE LAST sentence I typed CLEARLY says MOST. I know that there are blocks that use them. I was pretty sure the original poster was looking at the aftermarket Big blocks that to my knowledge all use a steel cap. I will go crawl back in my hole now. What was I thinking...Todd