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I'm a little baffled by this. I've been hearing for years that the 2v exhaust port actually flowed better than the 4v exhaust port. The opposite of what you are saying ?

4V heads flow better without a doubt! As Doug pointed out, 2V heads are purported to make more low end torque and offer snappier throttle response and off idle performance in a street driven Cleveland because the smaller intake ports allow for higher air/fuel mixture velocity at lower RPM's. But 2V heads will not outflow 4V heads!

More info on heads from Dan Jones at this link:
http://pantera.infopop.cc/eve/...700067562#9700067562
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This is one area where the "high port" Cleveland heads is superior to the original Ford iron head exhaust port configuration which turns them down. The 2v ports simply can't be made to flow equal to the 4v ports in any configuration.

The 2v iron head is worse then the iron 4v in that respect.

That's one reason why the 3v heads, 2v intakes with 4v exhausts are popular.



quote:
I'm a little baffled by this. I've been hearing for years that the 2v exhaust port actually flowed better than the 4v exhaust port. The opposite of what you are saying.


quote:
4V heads flow better without a doubt! As Doug pointed out, 2V heads are purported to make more low end torque and offer snappier throttle response and off idle performance in a street driven Cleveland because the smaller intake ports allow for higher air/fuel mixture velocity at lower RPM's. But 2V heads will not outflow 4V heads!



posted August 30, 2009
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The 4V exhaust port is an oddity of the Cleveland design, something we uninformed masses will scratch our heads about forever. Consider that the 2V head was an afterthought, it was designed by the same engineers who designed the 4V head but it has no gas bounce trickery in the exhaust port. The 2V exhaust port out-flows the 4V exhaust port measured in the conventional manner on a flow bench. But the 2V head does not have the same potential as the 4V head. I think the flow bench is a good tool for measuring the results of porting work, or for comparing one head to another, but it does not measure the head under dynamic conditions, with a piston going up and down in the cylinder, valves opening and closing, and combustion taking place etc etc. The engineers at Ford had dynamic potential in mind when they designed the 4V intake and exhaust ports. I guess the exhaust port design just didn't pan out as well as the intake port in real world use.


So which exhaust port flows better ??
Here's the numbers



That was me you were quoting. My comments weren't 100% accurate were they? The 2V exhaust port flows well on the bench, but it doesn't really out-flow the 4V exhaust port. Comparing ported heads, the numbers are quite equal up to 0.500" lift, then the 2V port predictably flattens out while air flow through the 4V port keeps on increasing.

If you wish to further discuss exhaust port flow, please start a new thread, do not take this thread further off-topic. I'll gladly move these last few posts to the new thread. And please keep it friendly and respectful.

-G
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Originally posted by Bosswrench: FWIW, engine builder & author David Vizard has written about headers several times in his various books, and according to his dyno tests, if the individual tube lengths are within about 6" or so, no power gains/losses will be seen.

Actually, if you are referring to his writings in his “Building Horsepower” series, when Vizard made this statement it was specifically in reference to dual plane crank V8s and conventional 4-1 headers. This is due to the asymmetry in how the exhaust pulse phasing arrives at the collector in a dual plane V-8. Though dual plane V8s with 4-1s are relatively insensitive to primary length, they can be very sensitive to collector diameter and collector length. In fact, collector length can be a very (if not the most) effective parameter in tuning such a system once the in car constraints and layout is fixed. When you go to 180 degree exhaust in the same V8, equal length primaries certainly does matter. However, this whole discussion must be footnoted with the fact that it is most often the case that it is impossible to achieve the theoretically optimal primary length because you physically cannot make equal length primaries reach the collectors without adding additional length. This is certainly true in Pantera’s and GT40s. The most popular embodiment for dual plane V8s remains the 4-2-1 or the Tri-Y, as most commonly seen in NASCAR. When done properly, they are very long for Pantera fitment though possible. The good news is you can still build a high performing zero-loss exhaust system within the constraints of a Pantera.
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What's more important is the fit of the individual tubes into the weldment. Sloppy tube fits buttered up with weld do not work as well as neat fitting 'fishmouth' tubes, and often crack. Further, mild steel tubes will expand and contract by as much as 0.060", and stainless even more, which is really what cracks poorly made headers.

In the same articles, Vizard also comments that 4-1 Dual Plane V8s are remarkable insensitive to dents in primary tubes, with sometimes no noticeable performance effect with even 60% of the diameter compromised. So all you sledge hammer mechanics rejoice.

Best,
Kelly
I purchased a set of Pat Mical headers and the joining pipe to the rear muffler. 3" collector which tapers down to 2.5" on mine and then v-band clamp to the mufflers. I did have some very noisy twin pipe mufflers that the fiberglass muck just continued to come out of. These are not from Pat or the ones he uses.


Pat Mical has modified a pair of my Hall Pantera euro Ansa mufflers that I had. He had to cut and then drill out where the old pipe came in and he welded a 2.5" stainless pipe in there with a v-band connector. Looks very nice and a lot quieter.


Pat also knocked out the plug that was at the very end of the perforated tube.
For something as coveted as ANSA mufflers, it continues to puzzle me why used, beat up relics continue to sell on Fleabay when Steve offers such a nice set. That said, I have seen literally zero marketing of his setup. Does anybody have any pictures of them installed?
Wilkinson removed the internal restriction. I think it was a 1-3/4" internal ring. I also think that was a sound reduction device on the original Ansa design.

When you increase the id of it, you increase the sound level emitted. There is some type of a graph on that somewhere?

Think of it this way, the additional sound is the 50 additional horses trying to get out.

I feel a sound level comparison coming on now in this thread? Anyone else feeling those vibes?

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