kirkyg said:
Alright, so if what you saying is true and other 'advancements' are making these 3valve 'god-heads' if you will...why is ford continuing to produce a more expensive to manufacturer DOHC heads for the all new cobra and lightning to be mated to a Twin Screw supercharger?????????
Explain PLEASE.
Oh, and no what really matters is if i take these 3valve heads and these 4 valve heads to a shop to have them p&p'd which ones will flow better and produce a better longer powerband? Thats what matters...not how well they flow stock.
kirkyg
Why stop at 4 valves? It's been proven that 5 valve heads are better, that's why most of the Formula 1 race engines use them.
Again, your comments about "porting" is just grasping at straws because you don't know how the heads flow and if porting really will gain you anything.
Now I will tell you the 2 things that ARE better about DOHC 4V and 5V heads.
1. With separate intake and exhaust cams you can implement DUAL variable valve timing. That is you can change both the intake and exhuast valve timing INDEPENDENTLY. This is what the BMW Dual Vanos system does and it is part of the reason why BMW can get so much HP out of the little M3 engine and meet emissions requirements. Porsche also has a similar system.
HOWEVER, Ford has NOT yet implemented any form of VVT on the 4.6 or 5.4 4V engines let alone dual VVT. So there is no real advantage here.
2. You can increase the angle between the valves, creating a larger distance across the bore which allows more valve area. More valve area means you can use larger valves. Larger valves mean you can flow more air. More air means more HP.
However to be fair, we have to talk about the downsides of DOHC 4V and 5V heads.
1. They cost significantly more. Remember we are talking about a $25K Mustang GT, not a $60K BMW M3 or a $100K Porsche.
2. They are physically larger.
3. They are physically heavier.
4. They have more moving parts. More moving parts means there are more things that can fail or wear out.
Every engineering decision made in designing a car is a compomise between price, performance and weight.
The bottom line is that the new Ford 3V heads are a GREAT compromise between performance, cost, size and weight.
Whining for 4V heats on a $25K GT is down right silly.
The Cobra and Lightning are EXPENSIVE special models, so they can absorb the cost of 4V heads.
Time to
this thread.