the man speaks the truth, I cant wait to see how much a rebuild is for the old 4v :noIsn'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?
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?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
.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.