The ever-so desireable 308 Heads
Let's all ask that question in 30 or 40 years.. We all know the cast can literally be used abused and confused while still being rebuildable. The cast is a lot more forgiving should a valve come loose, or the seats being beat all to snot the aluminum does not fare as well.
While aluminum does provide many performance advantages with weight, modern bowl work, valve sizes ect you can do similar to cast and still keep #s matching. Even at Edelbrock performer RPM level the 308 is a great of the shelf head for around 300 used per pair vs over 1500 per pair.
First, most folks don’t use their cars enough that it’s going to be a problem for them. And I don’t know if you’ve looked at the average age of members in this board, but 40 years from now not many of them will be worried about rebuilding aluminum heads. I’m on the young side of the average age for this board and I’ll be doing good to still be around in 40 years.
Next up, if an aluminum head drops a seat and it chews up the cylinder you just weld up the chamber and machine it. I’m not gonna say it’s easy, but it’s a better fix than what you can do with cast iron because when you’re done it’s as good as new.
And last, your price comparison is out of whack. In order to flow like an Eddy RPM out of the box a set of 308’s needs to have bigger valves installed with new seats, the bowls then cleaned up, and ported around the “stage II” level. At that point they’ll be pretty close to an Eddy RPM out of the box. And unless you did ALL of that work yourself, you’ve paid as much as it would cost to buy a set of Eddy’s.
How do I know? Well, because I bought a set of 308’s, paid less than $300 for the pair, then had them ported and rebuilt. They flow a little better than OOTB eddy RPM’s, and by the time it was all paid for it cost me just as much.
And that’s with eddy’s, that’s not even buying a set of Speedmasters on sale.
Unless you need OE heads for a racing class or really want a stock looking set of heads buying a set of 308’s is a fools errand. They’ll be cracked, so no matter what you’ll be doing seats, guides and cut to true them up. And then they’ll just be stock heads with a slightly better exhaust port.