5.4 heads on 5.8 block?

[GT Premi]

I didn't see anybody else ask, so I'll ask. What is the reason for putting 5.4 heads on the 5.8 block?

 

[TVS VERT]

 

[Catmonkey]

It a matter of buidling a short block from a 5.8 aluminum block from a 07-12 engine and not springing another $3,000 for bare heads, plus head work, or $7,000 for a complete set of heads. The only difference between the heads is those 4 holes BC posted. I couldn't justify the cost.

 

[Snoopy49]

2013 Ford Shelby GT500 Trinity 5.8L V8 - Power Of Three

Head Games

Relatively little work was required to turn the 5.4 cylinder head into the 5.8 head. In fact, from a power standpoint, the ports handled the increased airflow delivered by the increased boost and more aggressive camming, so no porting work was required. What was left for the SVT engineers was making the exhaust valves live through the resulting higher temperatures. This took development of the valves, valve seats, and cooling system.

We’ve already touched on the coolant passage improvements and that after extensive computer analysis the only mechanical changes were drilled passages to promote coolant flow between the exhaust valve seats. This sounds simple, but the engineers were set on evening coolant flow as much as possible throughout the cylinder head, and that entailed many computer simulations.

In the end, they were pleased with the 5.8’s top-end cooling as they got water flowing evenly between the exhaust valve seats, plus the coolant flow balance between the engine’s two banks is an even 49 percent on the right and 51 percent on the left (this is affected by water pump direction of rotation, which might also partially explain why cylinder No. 3 is always the hottest). Furthermore, this was accomplished with the first physical modifications as the development work was done completely in the computer. This saved tremendous time and money.

Getting the exhaust valve to live was done with improved materials and a little extra mass. Incredibly, the extra mass found on the combustion chamber side of the valve head is there simply to withstand the hellacious cylinder pressure. The original concave profile of the 5.4 valve deformed at 5.8 temperatures and pressures, so the head of the valve was made slightly thicker.

The harder valve material is Nimonic, trade name for a super steel alloy, along with a Stellite ring inlaid into the valve’s seating face. The Stellite is fitted to a groove machined into the valve face, and welded and machined in place. In the cylinder head, the exhaust valve seats were upgraded from W236 to W100 Stellite. That’s truly hard stuff normally found in “dry-gas” applications such as propane-burning engines. In the 5.8, the W100 is there strictly for its increased surface hardness as lubricity was not an issue.

To support the extra airflow coming off the 5.8’s larger supercharger, SVT employed the age-old expedient of reaching for an already developed and proven camshaft, or in this case, all four cams from the 5.4-liter Ford GT engine. These are more aggressive grinds than the 5.4 GT500 sticks, as seen by the gain of 1.1 mm of intake and 1.4 mm of exhaust valve lift, and the engineers say they really helped. No other valve train modifications were necessary, so the intake valves, all valve springs, retainers, roller-finger rockers, lash adjusters, timing sprockets, timing chains, tensioners, and pulse wheels are carryover 5.4 parts. The front timing cover is carryover as well, as are the valve covers and even the ignition system. Well, to help combat gap growth, the 5.4 platinum-tip spark plug has been replaced by an iridium-tipped plug.

 

[GT Premi]

2013 Ford Shelby GT500 Trinity 5.8L V8 - Power Of Three

So what did/does Shelby American, Inc. do to the 5.4 heads on the Super Snakes? Seems to me those engines would have to endure a lot more stress than the stock 5.8. Even FRPP sells a 750HP Whipple kit for the 5.4 with no requirements for all those changes to the heads. So why make the changes for the 5.8? I'm confused.

 

[Catmonkey]

Shelby does nothing to the engine. Super snakes mods are limited to bolt-ons. All the mumbo jumbo about cooling the exhaust valve had to do more with Ford's durability testing and their 200 mph claim than any performance benefit. It your car spends considerable time on a road coarse it may be worth it. But then how many engine failures have you seen on these cars that were valve related, that weren't caused by failed timing components?

 

[GT Premi]

So, essentially, SVT made the changes mostly "just because."

 

[2011 gtcs]

Shelby does nothing to the engine. Super snakes mods are limited to bolt-ons. All the mumbo jumbo about cooling the exhaust valve had to do more with Ford's durability testing and their 200 mph claim than any performance benefit. It your car spends considerable time on a road coarse it may be worth it. But then how many engine failures have you seen on these cars that were valve related, that weren't caused by failed timing components?

If you buy the basic supersnake package with just the 3.6 KB than Shelby doesn't touch the engine. You can do the holeshot package and they do cams and LT and some other small stuff to the engine and they claim to make 900HP at the flywheel. I have no idea how the hell they can claim that power and not change the rods out. I'm sure anyone who buys a supersnake with the holeshot package probably doesn't do anything with it and it just sits in a garage and doesn't move. You can also have them build you the Shelby 1000 engine in your car, But that's a extra 50K

So, essentially, SVT made the changes mostly "just because."

So the engine can handle long 5th gear WOT pulls to do 200mph

 

[GT Premi]

... You can do the holeshot package and they do cams and LT and some other small stuff to the engine and they claim to make 900HP at the flywheel. I have no idea how the hell they can claim that power and not change the rods out. ...

Well, Carroll Shelby said the engines can "comfortably" handle 1000HP. Maybe it's true. From what I understand, it's excessive revs that kill the rods, not power or boost.

 

[merkyworks]

Well, Carroll Shelby said the engines can "comfortably" handle 1000HP. Maybe it's true. From what I understand, it's excessive revs that kill the rods, not power or boost.

Haha so just rev it like an old school big block and shift at 5,500rpm.

 

[GT Premi]

Haha so just rev it like an old school big block and shift at 5,500rpm.

Pretty much. With that much power on a street car, what need is there to rev to 7K+ RPM?

 

[2011 gtcs]

Well, Carroll Shelby said the engines can "comfortably" handle 1000HP. Maybe it's true. From what I understand, it's excessive revs that kill the rods, not power or boost.

I would say the 5.4s and 5.8s can handle 800whp as long as you're not beating the hell out of it all the time, But the stock rods can not handle 900hp let alone a 1K HP for very long. I guess I'm more paranoid about hurting my 5.8 block because its almost 6k just to buy a bear 5.8 block. 5.4's are much easier to come by