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Priest of the Car Gods
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Anyone know what the differences between a 2v and 4v are other than the heads and two more cams? Just curious. Thanks
Aluminum block (4v) vs iron (2v)
Forged crank (4v) vs cast (2v)
Higher redline for the 4v
IMRC plates for the 4v
Higher compression with the 4v
 

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Not a Rational Car Guy
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Exactly in your title ;)

2V vs. 4V's in the heads :lol

But seriously, +1 to what Rev said. (except in the 03/04's the compression isn't as high)
 

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Not a Rational Car Guy
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Isn't it easier to just give the real answer.

2v$ < 4v$ but 4v> 2v.

Thats the real answer. 4v is better in every way than 2v, but it costs more to start playing.

If you want more details there are ALOT more details about the engines and the cars they go into but I have a feeling the short answer was more waht you wanted?
 

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Not a Rational Car Guy
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^:lol
 

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Isn't it easier to just give the real answer.

2v$ < 4v$ but 4v> 2v.

Thats the real answer. 4v is better in every way than 2v, but it costs more to start playing.

If you want more details there are ALOT more details about the engines and the cars they go into but I have a feeling the short answer was more waht you wanted?
the man speaks the truth, I cant wait to see how much a rebuild is for the old 4v :no
 

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Yeah. Does anyone else notice a wave of each type of questions. Each week there are a million posts about 1 subject. 5.4 swap, wait N/A vs FI, wait 4v vs. 2v.

Aluminum vs iron is pretty irrelivant, you can use all of them interchangably. The 03-04 cobra are iron, the 96-04 are iron block. The 03-04 cobra's have more webbing making their mains stronger but slightly heavier, but negligable amount so it doesn't matter.

Aluminum are lighter and require some slightly different bolts that are less likely to strip the block, and they are not recommended for as high power. But its over 800 hp so it doesn't matter.
 

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Discussion Starter · #13 ·
Aluminum block (4v) vs iron (2v)
Forged crank (4v) vs cast (2v)
Higher redline for the 4v
IMRC plates for the 4v
Higher compression with the 4v
By the way, I believe the higher redline is because of the heads being 4v. It gets more air so there are less resistance forces on the piston having to pull air into the cylinder. The timing chain cover is different too because the heads are wider, right? What exactly do the IMRC plates do?

And sorry, I haven't seen this post in a long time so I thought I would start a new thread.
 

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they are valves in the intake that open up when you go past i believe 3,300 RPM to allow more air flow when your gettin on it. Thats it in a nut shell, these threads are all over the place, youll find an in depth one
 

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Through the years these heads have proven themselves to be excellent high rpm (8000rpm+) performers—mainly in power adder applications--since their tremendous combined intake port cross sectional area and volume (when combined, a full 55cc more than any other 4.6L head design) provide for exceptional power production in the upper regions of the tach. Ironically, it’s those same big, beautiful, twin ports that also prove to be the B head’s largest inherent design flaw. The extra intake port size has a tendency to kill low/mid rpm intake port velocity and power production—hence the use of Ford’s first IMRC (intake manifold runner control) intake on the 96-98 Cobra. By allowing air to reach only one of a B head’s twin intake valves, velocity, and therefore low/mid range torque production was restored in situations under 3250rpm. Later head designs are clearly superior in this regard, which happens to be the one of the most important considerations for those wanting a stout street motor.

There is also some controversy over the single fuel injector/dual intake port setup. Some claim insufficient air/fuel mixing because of the compromised design, however, others contest that the ability to make 1000+rwhp with only minor porting and some form of power adder is testament to the contrary. Whoever you believe, there is little doubt that even after as little as 8,000 miles, carbon and other deposits tend to form on the secondary ports, causing a major airflow impedance, as there is no fuel present to clean them. B heads feature a somewhat small stock exhaust port that really hinders flow in power adder applications. Major gains from porting come with a quality valve job, some pocket and lots of exhaust work. There really isn’t a lot of material to remove from the intake ports themselves.

The Bottom Line: B heads aren’t the best choice for a naturally aspirated street motor. In order to really shine, they need to be paired with a power adder and a short block that can sustain high horsepower and rpm levels. These, the oldest heads, may still be a great choice for full race applications.
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