[miketan]

Originally Posted by Blown330

Strictly speaking, the other guy is correct. Talking around 20 lb-ft of difference based on the ratings given by the manufacturers...not much.

Man, you Ford guys crack me up! The Titan has 385 lb-ft of torque at 3400rpm. The 5.4L SOHC 3v has 365 lb-ft of torque at 3750rpm. Using 3rd grade arithmetic, that means the Titan has 20 lb-ft MORE torque at 300 rpm LOWER in the powerband. How is the other guy right?

If you look at the total picture you'd notice the that while the 5.4 would get a bigger hp bump from the 4V heads it would do very little for torque (use the 4V Navigator motors compared to the 2V engines for reference).

Looking at the total picture, I see that the 5.4L desperately needs HP not TQ. Going to a DOHC 4v per cylinder setup would increase HP dramatically. However, we're talking Ford here, so I'm not sure if it could be done. Look at the fiasco they had with the '99 Mustang Cobra's. The DOHC 4v 5.4L Triton seems to put out about the same HP/TQ numbers as the SOHC 3v engines. Maybe it's the variable cam timing that helps the 3v modular motors perform so well.. Maybe they should try VCT on the underacheiving DOHC 4v versions as well?

The 5.4's are built to make torque, they do that very well. With a 4.165" stroke (far more than the VK56's) they are not rev happy anyway. Just not an architecture that lends itself to making power n/a. To take full advantage of the 4V heads would mean trying to wring those engines well past 6,000 rpms.

365 lb-ft for the top tier gas powerplant is rather weak these days. Everyone else is at 375 lb-ft or higher with the top engine option. 400 lb-ft will soon be standard. You can always design a large bore/short stroke motor for more a torque, look at the Endurance. If HP was a primary concern, they could've easily upped it to 400hp+. However, the Endurance was primarily designed for relatively heavy vehicles so torque was more important than all out HP. However, it's hard to design a small bore/long stroke motor for high HP. Ask any 305 SBC guy. Alternately, I don't think you need to spin the 5.4L past 6000rpms to take advantage of 4v heads. If it had a larger bore, it would be easier to create more HP and retain TQ. That's why the 5.6L Endurance is a better engine overall. It has more torque at a lower rpm and still has more HP with just a tiny .2L displacement increase. Ford screwed up, but at least they got the frame right.

To put it in perspective, at 6500 rpms the 5.4's pistons would be moving more than 1,000 fps faster than the Titan's. The cost isn't in the heads, it would be putting in a rotating assembly and bearings to handle the stresses. They do love boost and nitrous though and psi for psi they respond better than anything else out.

I don't think you'd want the Endurance spinning at 6500+rpms either. The DOHC 4v heads do provide an advantage, centrally located spark plug location for optimum targeting. Also, there's no complicated rocker arm assemblies to reduce valvetrain efficiency either.

The '09's might get 4V heads along with a larger bore 4.6-based 5.0...all speculation though. The F-150's will finally be getting the "big bore" Modular they need so don't think that they will be behind the horsepower dept. for much longer.

I don't think that at all. However, it sure is taking them a long time to get competitive in the powertrain department. The current 3v Triton is an outdated small bore/long stroke design that needs major changes to the shortblock to support future HP increases. The Endurance just needs VCT on the exhaust cams, tubular headers, perhaps hotter cams and WOT ECU programming ala UpRev and 400hp/400TQ would be within easy reach. You don't even need to touch the all aluminum short block or rotating assembly.

As for the "more valves equal better breathing"...I really wouldn't use that assumption as the GM LSx and DCX Hemi heads outflow EVERYBODY with 2 valves. There's a lot to be said for applied computational fluid dynamics (GM does this better than anyone save Ferrari).

I would. It takes a larger 6.0L LS1 based Vortec engine to produce the same power as the smaller 5.6L Endurance. Remember, the Endurance is DOWNRATED by Nissan. The 2v pushrod design was probably deficient in the HP department, but had good torque. So they upped it to a jaw dropping 367hp for marketing reasons, but sacrificed TQ (only 375 lb-ft) in the process. The problem with GM and DCX is that they have to periodically increase the displacement to make any significant increases in power N/A. With a large bore/short stroke DOHC 4v design, you can remain at relatively small displacement levels and create insane levels of power.