Velocity is very important for a street car I guess but I have spoken to at least 3 of the top engine builders (ls1) in the country and all of them told me that if you just want to go fast, I'd much rather have a 250cc head flowing 350cfm than a 225cc head flowing 320cfm.

The AFRs are made for a niche. They are excellent heads as they come CNCed. But the AFR CNC job is not an all out head. The castings are improvements over the stock castings for which I am glad and thankful.

I just wouldnt use them on all out applications. Look at what people like Cartek and Futral etc etc are using on their big motors to make big power.

 

Flying Blue Dream hit the nail on the head....Look at the delta between the two heads....thats more important than comparing numbers from two different pieces of equipment (Flow bench variations). Bottom line is that both of these figures seem extremely low and I question which bench these numbers were taken from, who did the testing, what bore size was used, was a radiused entry used, was a pipe used on the exhaust (we use a 1.875 flow tube that bends and aims down just like a typical header)....etc...etc.

There has been many threads on LS1 Tech and I want to say a few on this site as well with independent results that state our heads flow exactly what we advertise and some have reported seeing more than we advertise. Your numbers are so far out of the realm of things that it makes me feel more comfortable that there is nothing wrong with them (versus saying they were 10-12 CFM away etc.).

We take what we advertise very seriously and our in house "Production" tolerance is 2%....The numbers we advertise in our catalog and website are very representative of what we ship out in a "Production" environment. A head that was CNC machined with new, very sharp cutting tools might flow 2-5 CFM better than we advertise....a head that was run right before the tools were replaced (they have a cutting tool life and an alarm that warns the operator) might flow 2-5 CFM less than we advertise. We stand behind that 2% rule if a customer has questions regarding flow such as yourself. Obviously if the head flowed 315 CFM (on your equipment) I wouldn't be typing this post because you probably wouldn't have had an issue at 315 CFM.

Our policy is such that if a customer/engine builder is questioning the flow of one of our products and is willing to send it back to us, we will flow and evaluate the head at no charge. If it flows within 2% of our advertised numbers, the customer is responsible for the freight both ways (but we do not charge for the time it took to test the heads). If the heads are in fact below what we advertise, we will correct those heads or build him another set based on what we find to be the problem. We will also cover all freight costs involved shipping to and from AFR. Also, as this would be considered a warranty kind of situation , the job gets special preference moving thru the shop so the inconvenience to the customer is minimized as much as possible.

I hope this post helps to clear up a few things and feel free to contact me if you are wanting to confirm that the heads you received are in fact up to par as they say. I have a strong feeling there are some other issues at play here....perhaps you might consider another local independent test if that isn't to much trouble, but either way, I would encourage you to contact me directly in the event you feel you have a problem

Thanks,
Tony Mamo
AFR Sales / Product Design Mgr.
(818)890-0616 Ext. 109