I've owned & rebuilt a fair number of motors (mostly when I was younger - SB Chevy, BB Pontiac, SB Ford), but a couple years ago I decided to rebuild the motor in my '98 Cobra.
When you pull apart the 4.6 DOHC it becomes pretty clear what 20+ years of engineering advances bring to motor design. Lets do some highlights:
BLOCK
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First off, this is an aluminum block with 4-bolt mains & 2 bolts through the skirts of the block (1 each side) & into the main caps. Effectively you have a 6-bolt main, aluminum block that you can easily huff around the garage without a hernia. Holy crap - when I was growing up this was an Indy engine!
CRANK
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The crank is a work of art. The thing is a solid steel from the factory! Not cast. Not nodular. Repeat after me S T E E L! Oh, and how about a GEAR (really not a gear, but not sure what to call it)
Oil Pump and a full WINDAGE TRAY - all stock.
HEADS
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All aluminum w/OH cams. The entire valvetrain length is about...zero! No 5" pushrod, big rocker or lifters - just a lash adjuster so you don't have to adjust the valves & a tiny roller rocker that is designed in such a clever way it doesn't need bolted down. Yes, I know its hard to believe, its even harder to describe, but once the damn thing is in place it gets sandwiched between the valve/spring, the lash adjuster & the cam. Viola, 8K RPMs with nothing holding it in place except the design!
Oh, and did we talk about the 4-valves / cylinder? Talk about flow, these things flow like race heads stock. Its relatively easy to make 300 - 320 RWHP with this motor naturally aspirated. I've seen 5.0's with blowers make the same #'s.
The rest of the motor is pretty reliable, but uses parts that aren't quite the race-ready parts the block, heads and crank represent. I will say though that the pistons & rods in these engines hold up fine to lots of boost if the mixture is controlled carefully. Here's an old dyno chart from my '98 4.6 DOHC Cobra with 10lbs of boost:
