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Discussion Starter #1
The ultimate cylinder head comparison is under way. The Sep issue of MM&FF began a six part series devoted to testing the most popular after market heads out there. It looks like a total of up to 30+ heads are being tested. They are divided into three groups depending upon their individual performance level.

Each group has two testing phases. One to establish air flow numbers and the other for actual tq/hp output.

The airflow tests are conducted by the same flow bench and operator on the same day. Each of the 3 groups will have it's own test engine. Group 1 had a 302. Group 2 a 331. And Group 3 will use a 347.

All testing is finished for the Group 1 heads. The AFR 165 heads came out on top. The Oct issue, which is out right now, has the airflow results for Group 2. Dyno numbers next month.

Anyone considering a cylinder head purchase might want to follow along. The testing will not tell you how a given head will work in your particular application, but for now the series has the most detailed comparison/testing that I've seen.

There will be some who will question the results based on their own experience or preconceptions. So be it. ::

The fact is, to my knowledge no one else has done it. So this is what's available.
 

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An additional test would've been to mount the engines in an identical test mule for at least two of the real world disciplines, such as drag racing or road racing, and bring the bench results into the real world. I'm sure there would be a number of VMF'ers willing to volunteer for such severe duty *G*

Thanks Joe..
 

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Discussion Starter #3
An additional test would've been to mount the engines in an identical test mule for at least two of the real world disciplines, such as drag racing or road racing.......
That would add some data no doubt. But as we know, once you drop a given mill into a car, all the bench/dyno numbers go out the window. Each and every Mustang on the VMF would post a different et/trap speed (supposedly). Lots of variables.

And I'm sure you're correct.....plenty of volunteer mules in line here on the VMF. ;)
 

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Aren't the AFR heads CNC ported right from the factory? If this is so what would the numbers be if the other heads where CNC ported from the factory?
 

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I can't speak for the road or oval racing crowd, but drag racing vehicles such as mine are very consistent demonstrators of engine operating parameters. The reality that different engines over the years have invariably operated within tenths of each other (like from 11.50 down to 11.20) and very consistently tells me I was building the engines to a similar performance level and the car was utilizing it efficiently.

Likewise, if we were to put a 650hp stroked W in the car, its performance would invariably improve in a consistent manner, like into the low 10's. That's what happens when one over-builds the chassis (in my case). I've just run low HP engines over the years for reliability and lower cost.

Running the engines in different vehicles, especially not dedicated racing vehicles, would definitely introduce the variables you allude to. It wouldn't be very scientific, but it would likely be fun for the owners *G*.
 

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The thing that I'm always curious about with many of the "shootouts", is the performance at lower rpm levels. Most of the dyno graphs seem to go from 4000rpm up - I'd much rather see them start at 2000. (To be fair, I haven't seen this particular article.)

Why? Most street guys would be better off with 10 extra ft-lbs at 2500, than 10 extra HP at 6500... Yeah, the big numbers sell parts, but mid-range torque is what moves cars (at least in a street environment).
 

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Discussion Starter #7
Most street guys would be better off with 10 extra ft-lbs at 2500, than 10 extra HP at 6500... Yeah, the big numbers sell parts, but mid-range torque is what moves cars (at least in a street environment).
I couldn't agree more. :D

Average flow throughout the desired power range is much more important on the street. Peak numbers just isn't the way to choose your heads. Most peak flow is well above the operating range of common street/strip engines.
 

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Discussion Starter #8
Aren't the AFR heads CNC ported right from the factory? If this is so what would the numbers be if the other heads where CNC ported from the factory?
The purpose of the series is to test a given heads performance in it's "out of the box state". I'm sure all the as cast heads would benefit from some cnc porting. But then they wouldn't be "out of the box".
 

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Most street guys would be better off with 10 extra ft-lbs at 2500, than 10 extra HP at 6500.

I've been preaching that for a couple of decades now, mostly falling upon deaf ears. My racing buddies were always amazed at how well my relatively mild and low cost combinations performed (at the track).

Small camshaft, good flowing heads and lots of compression are the main ingredients. Biggest problem most of my friends had on the street was too little compression and too much camshaft, everything else being equal.

The last part of the equation is efficient transmission of power to the ground. For the most part, street cars are lousy at that, in stock form. I could take the drivetrain out of the race car and put it in a street car and not come anywhere close to its performance. I would imagine most of the road racing guys here would say the same thing.

I recall some of my early posts, some 10,000 posts ago, saying it's the entire combination, not any one particular part or subsystem, which makes the vehicle an outstanding performer. That tenant still holds true, IMO.

Hey, enjoy! I'm leaving for Alaska tomorrow so cars will be the farthest thing from my head for awhile *G* I likely won't be back posting until we get back from London in 3 weeks. You'll survive without me, yes?? hehe
 
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