Ford uses two different main types of blocks, an aluminum one found in the Cobra and Mach one, and the iron used in the 03 Cobra and Gts. The main difference between the aluminum and iron blocks is weight. Both engines have been taken to 1500 HP with no problem. Ford chose an iron block for the 2003 cobra for that little extra insurance it’ll last with extreme horsepower levels. In my opinion, you should always opt for an aluminum block because of weight alone. SOHC parts can easily be adapted to fit aluminum blocks.
There are actually four versions of the aluminum blocks. The first is part number F6LZ-6010-AB used in the 1996-1998 and 1993-1998 Cobra and Mark VIII cars respectively. They are made in Italy by Teksid who also makes Ferrari engines. The block is an aluminum alloy of SAE 319; it weighs roughly 85 lbs.
The second-generation aluminum block can be found in the 1999 Cobra. The main caps in this block are slightly different as Ford took out the jackscrews. The width of the cap and different size bolt with a higher torque number are also changes in the new block. One thing should be noted that if a 1996-1998 Cobra or 1993-1998 Mark VIII is using this block, the knock sensors will have to be drilled and tapped since the knock sensor holes are smaller than the knock sensor bolts found in the earlier cars. The part number for this block is XR3Z-6010-CA.
The third generation aluminum block is found in the 2001 Cobra. This block is even lighter, weighing in at an amazing 80 lbs. Ford still uses the same SAE 319 aluminum alloy but they add some special ribbing around the block and main bearings. The oil drain-back holes are different in this block, keeping the oil further away from the crankshaft. So far, this block is still experimental; Sean Hyland reports using this block up to 600 HP but because of the lightening and ribbing to “help” it, I would not recommend this block for high HP. I also do not have the part number on this block. I do know for a fact, however, that it can be used up to around 800 rwhp.
The fourth generation is the new Mach 1, Explorer and Marauder block. While the exact information I have is somewhat lacking on this new block, it is slightly lighter and slightly weaker than the 1999 and 2001 Cobra block.
There are three different iron blocks in the SN95 mustangs, however, given my limited information on them, I will only be talking about two and lumping them all into one paragraph. If anyone would like to contribute more information on the blocks alone, please email me. Romeo and Windsor are the two block manufacturers for the iron blocks. The only main differences between these two are the main bearing caps. The Windsor blocks (made between 1999-2000 due to a fire in the Romeo plant [some did leak out in 2001 and maybe even 2002. Check your VIN to make sure]) have a torque-to-yield side bolt that can only be used once. Basically if you reuse it, you’ll break it. The iron block weighs 154 lbs.
Iron blocks should not be bored out beyond .030 inches due to the cylinder bore. The aluminum blocks have a Siamese bore; this basically means they are not hollowed out between the cylinders. So far, the only method I know of boring out aluminum blocks is by sleeving (you can bore an aluminum block up to .035 over without sleeving but unless you’re align honing and cannot obtain a good cylinder “straightness”, it’s not really worth it). These blocks can be bored out to 305 cubic inches or 5.0 liters when sleeved. The benefit is the valves now become unshrouded. This means that the bore is no longer choking the heads. If you look at the head and put it on a stock block, you’ll see that the valve-area is actually bigger than the cylinder in the block. If you want displacement with the ability to rev high, my advice is to go with boring.
Short and sweet, stay away from Stroking the motor. The 4.6L’s piston speed and rod length are
far too great to begin with. Hell, the
stock stroke is 3.543’’ to begin with.
That’s about the same as a 351 Windsor motor! They have an extra 73+ CID on
the modular motors. This puts it in perspective on how extreme the stock stroke
already is.
Now,
combine that with a stroker kit and your piston starts leaving the bore. This
is VERY bad at high RPMs as the piston becomes extremely unstable. Stroker
motors just don't last. The HP/TQ gains are so minimal as well because the
valves are still shrouded. The only time you want to use a stroker is when you
have a turbo setup as turbos don't really like to rev high either and can
benefit heavily from the slightest torque band increase. The reason these are
so popular though is because you can use your stock block and you don't have to
resort to using the more expensive aluminum block counterpart like you have to
in a big bore.
The connecting rods in 1996-2004 Mustangs and 1996-2001 Cobras are made by pressed powder. Yes, that’s right, pressed metal powder that is then machined. The rods just plain suck. When the rods go, they literally turn to powder. When building an engine, forging is the way to go. Unless you are going to exceed 700 HP or exceed 7000 RPMs, the best “bang for the buck” rod is the Manley H beam. When more HP is expected or higher RPMs are wanted, go ahead and skip the “Manley Sportmaster” rod and go straight to the Pro –Series Billet I-Beam. This rod can withstand 1200 HP and 9500 RPMs. If you want even MORE HP and MORE RPMs, John Mihovetz custom makes a 300M series rod that supports over 1600 HP and 10,000 RPMs.
Pistons are what separate us 4.6L guys from the 5.0L guys in terms of strength. Except for 1993-1995 5.0s, 5.0L cars came with forged pistons right out of the factory. The 4.6L pistons (except for the 03/04 Cobras) are hypereutectic pistons. Basically they’re aluminum pistons with lots of silicon in the mix. If these pistons see detonation, they blow almost instantly; the strength is just not there. Diamond, JE and Manley are great pistons to choose from for the entry level forged motors. These can withstand around 700 HP. If you would like to rev higher than 7000 RPMs and/or have higher HP in mind, go with CP pistons. They can custom make pistons for your application.
2V pistons are 11-cc dish and 4V Cobra pistons are 3-cc dish. A flat-top piston will bring a 2V up to 13:1 compression where as they’ll bring a 4V to 10.5:1 compression. Dome style pistons cannot be used in 2V engines due to a poor intake/spark mix in the combustion chamber. The stock piston rings are fine for N/A engines and moderate HP levels but when exceeding 500 HP, I recommend going with plasma-moly rings specially made by various manufacturers.
The GT, Automatic Mach 1, Marauder and Mark VIII all come stock with a cast crankshaft. 1999 and 2000 GTs had an 8 bolt crank where as the rest had 6 bolts. The cast crankshafts are very weak after 500 HP and cannot rev much higher than 7000 RPMs. When rebuilding an engine, it is worth the extra money to switch to a forged crank regardless of your setup.
The Cobras come with a forged
crankshaft that can withstand up to around 1500 HP and revs of around 8500 RPMs
with proper preparation. These are all
8 bolt cranks too. ModMax makes some
after market crankshafts that come with a variety of options ranging from shot
peening to heat treating, polishing and even lightening. For the average user, these are not worth it
but if you’re building a professional racecar, you might want to look into
it. A cryo treated, shot peened and
polished Cobra crankshaft will be bullet proof. It will NOT break even in excess of 2000 HP and 10k RPMs.