How much better is the three valve over the two?

[svtash]

I don't know too much about the three valve engines but it seems sort of strange that they are using three valves. What is the purpose of the third valve. Wouldn't airflow still be restricted (either in or out, not sure if there are two intake or two exh.)? Wouldn't it have been just as easy for them to go to the 4v since it already exists in the cobras? Someone help me understand their reasoning behind this. Thanks

PS if you think this is a dumb question please dont post anything and waste my time with this childish name calling thats been going on here lately.

 

[Ernad]

You stupid son of a.....















J/K
I believe they are two intake one exhaust. There is more flow, hence the jump to 300hp. I believe those heads are used on Ford Trucks. As far as using a Cobra motor, it probably comes down to being cheaper using the 3v.

 

[Stang8URMPRT]

Yes, the heads are straight off of the new new F-150 5.4 with the 3 valve heads. They are the same thing. One reason they use 3 valves instead of four is the 3 valves can be motioned by 1 single overhead cam, instead of the 2 on each head on the 4 valve head. Also, in extra chains that have to drive the other cam on a 4V, it saves Ford money, keeps costs down, and you get the power of the last gen 4V N/A Cobra motor. Works great for both producer and consumer.

 

[351CJ]

We've covered this subject several times before, but to add to what Stang8.......said.

The 3V gives almost the same HP & torque as the 4V heads.

3V head is significantly smaller in physical size.

3V head is significantly lighter (60-70 lb for the complete engine)

3V head is lower cost to manufacture

It uses 2 intake valves and 1 exhaust. This is because it is much harder to suck air into a cylinder than push exhaust gas out. 2V and 4V heads have larger intake valves than exhuast.

Bottom line is that if Ford had to use a 4V head to give us 300 HP, the 05 GT would sticker for more than $25K

 

[RandyB]

Because the upcoming 5.4 will only fit in SOHC 3V trim.

I hope that is the reason anyways...

How about an optional 5.4 3V N/A 350 hp engine for the GT? Put the blower on for the SVT...

 

[Stang8URMPRT]

If you take Motor Trends dyno results (not knowing if it's a Mustang dyno or a dynojet, but we'll make it a dynojet) and factoring in 20% loss in the auto (I dunno if this is the right %, but should be close) you get 320 HP at the flywheel. THey dynoed 267 at the wheels. A little under rated. Even sounds nasty with the stock exhaust system. They should be real quick. low 13's.

 

[new22003]

Its not a dumb question so don’t be afraid to ask it. 3 valves are strange as most people associate a cam with running only 2 valves. There are even some DOHC 5 valve engines out there (various Ferraris and a few motorcycles). As pointed out it is a good design that can still be operated by one cam thus making it cheaper and easier to set up. There are also advantages for emissions in a 3 valve versus a 2 valve.

One is not necessarily better than the other for power production though. There are emissions and other requirements to think about. People always seem to associate multi valve engine with making more power but this is not always the case. Heck pushrod engines (2 valve engine like the LS1’s, 5.0’s, etc) can produce as much or more horses than an SOHC 2/3 valve or DOHC 4 valve engines.

The two-valve has proved it can be built to very high power levels. I’m sure the 3 valve will also catch up to it in the aftermarket so not to worry if you are thinking about a purchase. I don’t think ford switched to a 3 valve because they couldn’t reach their 200 horsepower target with a 2 valve and still make emissions. Some tuners have actually said that all things being equal that the 2 valve can produce as much if not more than the 4 valve.

This comes from a very knowledgeable source. (Tim of Modular Powerhouse one of the best sources for modular mustang info)
http://forums.stangnet.com/showthread.php?t=508755&highlight=2.2

 

[jacob_9]

PS if you think this is a dumb question please dont post anything and waste my time with this childish name calling thats been going on here lately.

why would anyone insult you for asking a legit question?

 

[holler]

It's not as uncommon as you think, most mercedes use a 3 valve design.

 

[DBMSTNG]

due to the bore size of the 4.6L engine (3.55"), it's harder to get an intake charge with only 1 intake valve. (5.0's and Chevy 350's/346's have around 4" bores which makes it easier with 1 valve.) so the 2V is limited as far as creating hp without losing low end torque. with the 3V, it clears up the issue of the intake charge.

 

[mustgt88]

how much better is 300hp vs 260?

 

[Scott_B]

how much better is 300hp vs 260?

Id say 40hp better

 

[spectravp]

how much better is 300hp vs 260?

Considering we're getting 40 more horses without any significant change in price and the same, if not better gas mileage, I'd take those 40 more horses any day of the week! I think it's great!

 

[jacob__9]

how much better is 300hp vs 260?

it depends on if we are losing 40lbs of torque to get 40hp.

 

[SVTdriver]

it depends on if we are losing 40lbs of torque to get 40hp.

But we are not. We are actually up to 320tq.

 

[Scott_B]

Well it car is rated at 315 or 320 ftlbs, cant remember which. but i do believe thats more the previous years..

 

[Zoomy1]

it depends on if we are losing 40lbs of torque to get 40hp.

I believe the GTs are rated 300hp 315/320ft/lbs. Nope not losing any torque.

While we're on the subject since the top end is the same. How different are the short blocks between the Triton 5.4 and the 'stang 4.6. I wonder if you could swap the cranks? same heads, same cam, same bore. That would be a pretty cool mod to me. That'd be really cool if you didn't have to trade the short blocks.

I'm waiting till next year to buy.....since I'm on deployment until December anyway. Can't wait to see what the aftermarket can do with this.

 

[svtash]

Thanks guys for the info. appreciate it.

 

[RydeOn]

A LOT better. In my opinion the 3v is superior to even (dare i say it) the 4 valve motor. 300 HP is basically the same as a 4 vavle but you have less weight, simpler maintenence, half the parts to replace if stuff breaks and more room under the hood. The new intake design looks awesome too. These factors all together make it what is the best NA Mustang motor right now.

 

[351CJ]

The DOHC 4 valve has only 2 advantages:

1. VVT that independently varies the intake and exhaust valve timing can be implemented.

However as of today this is a non issue for the Mustang because Ford has put VVT on the 3V, but NOT the 4V, so as of today the 3V is better in this regard.

2. You have higher maximum airflow with the 4V heads. So the 4V can have higher peak HP, but it will occur at a higher RPM.

I agree with RydeOn, as being sold today, the 3V is a better engine for 99% of Mustang customers.