Originally Posted by MYBLKSS

In addition, can we also say that if the AFR 205's spec out that they are the only true effecient (performing) head.

Originally Posted by Kevin'

Based on what actual hard substantiated facts are the 236cc heads creating more power compared to brand [x], and at what rpm are the peak tq/hp being made? In order for us to get anything out of this thread we all must compare appes to apples and oranges to oranges.

I guess this means we would have to define the test parameters before we can reach a conclusion of any kind. Such as a test specifically for cylinder heads that fall into the engine-car combo in an H/O Street category, and then a test for cylinder heads that fall in the Weekend Warrior engine-car category. Then we would have something conclusive to make an educated purchase.

What tests have you seen where a side by side test has been performed regarding head testing on an actual running engine on a dyno? The only LS1 tests I've seen involve intake swaps and cam swaps - I've not seen any Cyl.Head swap testing to an LS1...as of yet (Hopefully the performance mags will pick up on this void).

Actual Port Volume cc does make a difference as well as volumetric efficiency - granted the LS1 is a unique engine in a class all its own. GM out did themselves and suprised the entire world with another Push Rod engine that kicks butt, but - the point I am making is this: peak power in a specific rpm range depends on matching Dynamic to Static CR relationship with the Port Volume, based on the Port flow relationship to the cam profile, within a specific level of performance desired: at a specific rpm. This means matching port pressures to cylinder pressures to engine rpm.

That is a good point about the stock LS1 not making its peak torque till around 4000 rpms!

If people are willing to spin their engines to the 6000-6600 rpm range, yee-haw, I say go for it. Yet if they are utilizing a port volume that is too large whereby that cam profile and cylinder head port volume dictate a peak hp in the 7000+ range (due to mismatched parts...or a misunderstanding of how to match the Dynamic to Static CR, Cam Profile, Cylinder Head Port Volume, then your engine is not running at peak performance. It may run well, but it is not running at maximum efficiency. Most will install a 285 or 290 cam with the larger heads...this typically dictates a peak 7000+ peak hp rpm.

To determine maximum efficiency we rally need more than just Tq/Hp numbers. We need Cylinder Pressures, Volumetric Efficiency, and Air-Fuel Ratio numbers.

The 236 heads on a normally aspirated stock 346 displacement engine requires 12:0:1+ plus Static CR to maximize the peak potential of those heads in a 3600 lbs car including driver.

Port Volume of a cylinder head has everything to do with peak rpms. If you dont understand this concept then you dont understand airflow velocity....and I know you understand airflow velocity.

I thought this thread's theme was about a few folks who purchased the 236cc head which hurt their performance and that one or two members said they thought they were getting a much smaller cc port(?) to begin with: this is the point I am making - most folks dont know they have to spin their engines to the 7000+ rpms to obtain peak hp: most folks just want to have fun never understanding there is more to building a performance engine than simply slapping on a set of heads.

If you dont mind rev'g your engine to 7000+ and you have a budget whereby you can repair things when they break, then I say go for it: just dont expect real performance under 4000 rpms.

As long as this lack of power under 4000rpms is disclosed to the consumer then all is well. It looks, according to this thread, that this information is not being disclosed to the consumer - so all is not well.

Is that the fault of the head porter...not always. We as consumers must be more educated. When we tell a speed shop what we want - we better understand what we are saying: because most speed shops are long on reputation and will give you what you ask for.

I still say, if you have a pair of the 236 heads then you should utilize Nitrous. The extra volume is perfect for the stuff.

If you are not going to do the Nitrous, Turbo, or Supercharger then the 236 heads are too large for a street engine on pump gas unless peak 7000+ rpm is your goal while anything below 4000+ rpms are inconsiquential: AND - you know this going into the purchase of these heads, then all is well.

Kevin'

Originally Posted by Bo White

Mine before any work-stock was 199cc and 75cc on the exhaust. I will post my ported cc shortly. I agree about the average cc among head porters, almost all are ported in the same areas the same amount. The valve job is what separates the men from the boys.

Originally Posted by cary et performance

I agree,

I've been working on these ls heads since they came out, and I'm very happy with the afr porters version,(I wish I could get the 30 sets I ordered) but nonetheless, I have been developing a couple ports in the afr casting and I am very happy with the numbers I am getting out of their casting. The problem we have with the 5.3 heads is when we program the model head, two heads later wont clean up, so you go in and change your program to clean up that spot, and three heads later, another bare spot. By the time you are done cleaning up bare spots, your at 230 + cc. We had 320 @.600 the first day with their head and a 2.02 valve, I never thought that would happen with that valve coefficient.

Originally Posted by Bo White

I can agree with that statement. Looks are very important to customers because when a port is visually awesome that just makes the feeling they had buying those heads from someone alot better and when cylinder head porters know this they go that extra mile to make the customer happy by spending an extra 5 min. on each port. Because that is the bottom line, making the customer happy with your product in every way, looks and function. When the competition of cylinder head sales are like they are you try to separate your work from others anyway you can to have the edge.