Cooler Heads Prevail
It's impossible to see the...
It's impossible to see the new exhaust valve seats in the 5.8 cylinder head, and while SVT says its adjusted some of the existing cooling system holes to tweak the coolant flow end-to-end in the cylinder head, we couldn't visually identify those changes either. Remaining steadfast to the 5.4 architecture paid off in the valvetrain as with the cams, crankshaft, and everything in between in the same place. The timing chains, associated drive parts, and even the front cover remain 5.4 carryover parts in the 5.8.
Buyers of 2013 GT500 Shelbys will have their choice of two oil cooling systems. An oil-to-water system is standard on every GT500, while an optional Track Cooling Package reconfigures the oil cooling to oil-to-air. Both systems have their advantages, and one is not really better than the other, they just meet different needs.
For regular street driving the standard oil-to-water system is the smart choice. For starters, it's included in the price of the car so it costs less. And by transferring the oil heat to the water in the engine's regular cooling system you are assured rapid oil warm-up in the morning (a good thing, especially in cold climes) plus stable oil temperatures. Total engine cooling, both water and oil, is more than sufficient to meet any street driving need and some track driving as well. Certainly the typical daily driver Shelby enthusiast who indulges in the odd autocross or test-and-tune night at the dragstrip will be well served by the standard oil cooling.
If the oil-to-water system has a downside it's that all engine cooling--both water and oil--goes through the radiator. This limits ultimate cooling capacity which can be reached in protracted track sessions. Therefore, track-day fans, and perhaps the handful of Southwest desert drivers who habitually hard-charge through the saguaros are the intended market for the air-to-oil Track Cooling package. The big advantage to the air-to-oil option is greater total cooling capacity. The radiator becomes "larger" because it no longer has to shed oil heat, just engine coolant heat. Meanwhile, the oil gets its own cooler, so the total heat exchanger area to the atmosphere is increased. In fact, SVT notes that with Track Cooling the 5.8 has about 20 percent more cooling capacity than the 5.4. Of course, the option costs more, but it's a must for the open-track crowd.
SVT saved considerable work...
SVT saved considerable work by not machining the combustion chambers to match the new larger bore diameter. The result is a lip of material not covered by the head gasket, but it hasn't amounted to anything in testing. But it sure illustrates how a 93.5mm bore on 100mm bore spacing leaves but 6.5mm between cylinders. This narrow area is especially tough on the head gasket and block; engineers found cross-drilling the block to water-cool this area was mandatory to block and head-gasket longevity.
How SVT offers the two oil cooling systems is rather clever. Bolted to the left side of the block is a convoluted aluminum casting full of passages and mounting the oil filter. With standard cooling, this snake-like casting also mounts an oil-to-water heat exchanger, which looks rather like an aluminum brick. The casting also offers hose nipples for piping the coolant between the radiator and the oil-to-water brick. For Track Cooling the oil-to-water brick is replaced by a thermostatic housing. Furthermore, the hose nipples are exchanged for threaded plumbing fittings to connect with an air-to-oil heat exchanger mounted in the front of the car, behind the grille. In this way, the casting's passages are converted from water to oil galleys, and SVT doesn't have to build another adaptor. In all, it's a creative use of resources.
So what about a car with standard cooling that gets open-tracked. Will it overheat and hurt itself? No, says SVT. Copperhead will start closing the throttle and limiting engine speed when the coolant hits 251. If the driver persists, or there is a mechanical issue such as a punctured radiator, the PCM can deactivate cylinders into a limp-home mode.
For the concours crowd 20 years hence, we'll note the 5.8 dipstick has a couple of extra marks in it for "overfill" use by the assembly plant. Jeff Albers explains, "We fill the engine with oil at the [Romeo] engine plant and don't top it off at the vehicle assembly plant [Flat Rock]. At the vehicle assembly plant [if Track Cooling is ordered], we add the cooler lines, so when you fill that with oil, the level drops. So, the two engine codes have two different fill levels. We support that so Romeo Engine Plant can do a quick visual inspection on the dock of the oil fill level... we added some other indicators that don't mean anything to the customer, it's just for internal check. That's why those extra marks are on there."
For the record, it takes about one extra quart to fill the lines and the cooler. The oil is full synthetic 5W-50, which can survive up to 300 degrees. Typical oil temperatures are 200 with the oil-to-water cooling, with 230 being the useful high end for that system. Extended track driving will raise oil temps closer to 300, which is why open-track fans need the Track Cooling package.
There wasn't a pair of 5.8...
There wasn't a pair of 5.8 valves available for photography during our SVT visit, so this pair of 5.4 valves is standing in for them. In the case of the intake valve on the left, it doesn't matter as the 5.4 valve is carried over without changes to the 5.8. The exhaust valve at right is at least a visual twin to the 5.8 valve from this angle, but the 5.8 exhaust valve is made from stronger, more heat-resistant metal, including a super-hard inlay of Stellite around the seating face. The 5.8 exhaust valve head does not have a bowl like the intake as that area has been filled in for strength.
Increased cylinder pressures...
Increased cylinder pressures in the 5.8 required new, harder head bolts to maintain the clamping load on the cylinder head gasket. They reduce head lift an extra 6 to 7 microns. Still, the 5.8 head lifts more than the 5.4, so an upgraded MLS head gasket from Federal Mogul was required. The 5.4 gasket uses three active and one inert layer; the 5.8 gasket adds an extra active layer, the better to remain in simultaneous contact with block and head when high combustion loads are doing their best to separate them. The engineers say the extra gasket layer really helped.
Matching the new entry into...
Matching the new entry into the blower case is a new SVT-designed blower inlet. At left is the 5.4 blower inlet; the more D-shaped inlet at right is the 5.8's. The new inlet is 33-percent larger and much less restrictive to airflow in this critical, naturally aspirated section of the inlet air path.
When asked if the 5.8 would be used in any other car, Jamal Hameedi replied, "It will only be a GT500 engine. That's pretty cool for a buyer of this car because, you know, you go out and spend a lot of money on an AMG or... another domestic car company and you buy a performance car and that engine is in a lot of different products. And when you go out and buy a Shelby, there's only one place, and that gets back to the SVT exclusivity pillar that we offer. And it's a special engine. The most power V-8 in the world, right?"
As for how many 5.8's SVT might bring into the world, as usual with SVT, that depends on how many of us show up at the dealership. "One less than the demand" was the classic SVT answer to the "how many" question, and it's just as operational today. In real terms, the GT500 sells a bit above 5,000 cars per year; we'd expect the over-achieving 2013 model to sell a few more as the Shelby extends its appeal. It will make one heck of a Ford Racing Performance Parts crate engine, too.
There's no doubt the new 5.8 modular is the most powerful V-8 in current volume production, but depending on how you want to parse the phrase "volume production," it might not hold the record.
In our personal experience, the 427ci V-8 in the Saleen S7 was rated at 750 hp and it was a production engine, albeit truly limited production. The Saleen V-8 was emission-certified in the U.S. and Europe, was warrantied, and Saleen produced and sold roughly 30 such Twin Turbos before the S7 lost its crash certification due to lack of a passive restraint (airbag). Saleen VP of Engineering Billy Tally developed the S7 engine from Ford Clevor architecture and it made its 750 hp in a walk; boost was but 4.5 pounds. We witnessed an engine dyno verification of a track-only (not emission-legal) special-order S7 engine that had nothing more than the wastegates screwed down to 8 pounds of boost. It made 1,012 hp.
A surprising number of other high-powered contenders turn out to be V-10s or V-12s, such as the Viper V-10, which doesn't equal the 5.8's power in any event. Then there's Chevy's ZR1 Corvette V-8, boasting 6.2 liters of displacement and the same Eaton 2.3-liter supercharger as the Ford 5.8, but coming up a hair short at 638 hp. Mercedes Benz has turned out some hefty V-8s, but not equaling 650 hp. Shelby Super Cars SSC Ultimate Aero has used blown or turbo'd small-block Chevy derivatives variously rated in the high 1,100hp league, but we seriously doubt these are emission-legal engines.
Koenigsegg, a Swedish supercar builder, has produced a 904hp twin-turbo V-8 certified for European road use, but it's never been legalized in the more restrictive North American market. Like the Saleen S7, the Koenigsegg is produced in numbers Ford would consider appropriate for prototype testing.
The same can be said for the Danish-sourced Zenvo ST1, which uses a bespoke aluminum version of the Chevy LS block, a supercharger, and two turbos to post a 1,100-plus-horsepower rating. But with only 15 cars scheduled for production, significant secrecy around the entire project, and North American emissions doubtful, it's not our idea of a production V-8 either.
We're sure other boutique V-8s can challenge SVT's 5.8-liter on horsepower, but none come even laughably close to meeting Ford durability standards, pricing, warranty service in one of several thousand dealerships across the U.S., or production by the thousands. When it comes to the most powerful real-world production engine, SVT's 5.8 is the one to beat.
There's nothing trick in the...
There's nothing trick in the 5.8 throttle body; it's the same 2x60mm twin-bore throttle body used on the 5.4. SVT says the air-filter box, mass air, and inlet tube also proved up to feeding the 5.8, so they carry over as well.
In a big step forward, SVT...
In a big step forward, SVT has moved to the 2.3-liter Eaton TVS supercharger pullied for 15 pounds of boost. Obviously the blower's outer housing is an SVT-specific casting, but there's more to it than adding logos and laying out the rib pattern. SVT computer modeling showed the short-turn radius on the blower inlet critical to airflow, so this area was enlarged and carefully shaped. In this photo, the blower inlet is the large opening at the right end of the assembly. The intake manifold and associated charge cooler water plumbing below the blower are carryover 5.4 parts.
We asked SVT if it would machine...
We asked SVT if it would machine smooth and bright the "SVT" and "5.8" so prominently cast into the supercharger housing and they said they'd leave that to owners as they were, "more function than bling." The extensive ribbing is some for looks, some for strength and some for reduced noise. Asked if the ribbing really made that much difference in noise transmission and Jeff Albers said, "Get that wrong and you'll hear it in the driver's seat." So we guess it matters.