Jack of Dart fame and Jason of Brodix both say iron=aluminum these days and why that is true. Note too what Dart says about a back-to-back test. Perhaps that's why Jay hasn't seen any difference: all his FE blocks are modern creations and not 30-40 year old versions of essentially old FE cast iron blocks.
"Aluminum Blocks
Jack McInnis: "The perception that aluminum blocks lose power through decreased ring seal, as compared to iron blocks, is largely based on early aluminum blocks, which lacked the integrity we can achieve today. Aluminum blocks might have sacrificed power many years ago, but that's not the case anymore. A properly engineered modern aluminum block will make the same power as an iron block. We were recently involved in a direct comparison test with a big-block dragster engine making in excess of 1,100 hp. The engine was assembled and dyno tested with an iron Dart block, then disassembled and rebuilt using an aluminum Dart block. At the end of the day, the power figures were nominally identical for the iron and aluminum blocks."
Jason Neugent: "In the early days of manufacturing aftermarket aluminum blocks, the material that was used did indeed move around a lot under heavy abuse. This caused the cylinder sleeves to move, sink, or go out of round. The consequence was that this deflection would cause water leaks and poor ring seal, which are prime ingredients for poor reliability and power loss. Today we have solved these problems with the use of our virgin A-356 aluminum recipe, tighter tolerances, and more rugged sleeve materials. In independent testing, Brodix has witnessed our own aluminum blocks seal as well as a quality cast iron block.""
That's all fine and good except for the fact that we are seeing horsepower differences *now*, not years ago. I also wouldn't say that new aluminum blocks are copies of 40 year old factory pieces. The 40 year old factory pieces don't have lifter valley ribbing, etc, etc. I know that Pond also uses a 356 alloy.
So what's "nominal" at 1100?
? 25 hp? 50?
Since we're offering up quotes, here's one from Darin Morgan from a few years ago on Speedtalk:
"We see the EXACT same thing. The Billet blocks are the only aluminum block I have seen that makes the same power as a cast iron block. Aluminum blocks take longer "season" and stop moving around as well. The second or third rebuild always nets anouther twenty HP. Also, as the aluminum block engines get hotter on the dyno the crank case pressure rises dramatically and the power goes south in a hurry! They just expand and move around so much its impossible to maintain any semblance of stability." Im assuming reher Morrison has some experience with aftermarket block offerings.
A lot of guys always point to the OEM on how well aluminum blocks work, but I will say that the OEM spends millions upon millions of dollars on R&D for one particular engine. They will also give up a few ponies in order to recoup some much needed fuel economy.
The thing that bites my booty is that guys are always eager to spend so much money on aluminum pieces. A few years back on Club Cobra, I asked the general population why they were willing to pay so much for them. The majority vote was for "bling" purposes. All I can say is that there's a lot of guys out there with money to blow, if they're willing to spend an extra $4000 to just say "I have an aluminum block" or to justify that they need 100 lbs taken off the front of the car.
I had 3 issues in a row with some aluminum FE blocks. Two of them cost me lost time and one cost me a nice little chunk of money. I decided after that, that the other builders could take all the all-aluminum FE orders.
