are you saying that there was something wrong with the castings? or that AFR is lying, or are the numbers just different because AFR lists them using a pipe?

On my flow bench the intake numbers are very close to what is advertised by AFR, within 1%


All of the AFR castings I have seen have had ridges from the cnc process in the exhaust seats, which is a very sensitive area for airflow. Also equally important is the overall volume in the exhaust port. A 300 cc intake port will no way flow 400cfm at .650 simply because of lack of volume, same with an exhaust port. In general ports need volume/area to relive pressure.


AFR claims 330 CFM @28" with a 2 1/8 by 6" pipe using a 1.880 valve. On my bench they will flow 300CFM @28" with a 2 1/8 by 6" pipe, without the pipe there about 270 Cfm.


To make a point, I just finished a set of Pro Topline heads 1.880 valve that flowed 323CFM with no pipe. With my cool guy 2 1/4" single steped, double bell mouthed 6" pipe it increased the port to an HTG 400 CFM @28". This tells me "A" a 1.880 will flow well over 300 CFM with enough volume and "B" my pipe flows more air than their pipe which is why I don't use a pipe to flow exhaust ports.(although I have an idea for a twin steped design).

I would never accouse AFR of lying

I agree.

Now I'm confused. I don't see any AFR heads that they claim flow anywhere near 330cfm on the exhaust side. The most I see is on their 357 cnc'ed of 325 @ .800 lift

Thse are fantastic increases for these heads.(265 stock I think) Which are they? The 320's or 360's, and how well did they improve overall to porting?


Final question. What is AFR's reason for showing numbers with the pipe on the exhaust, as no one else seems to publish numbers this way? Based on what you have found it looks like the pipe increase cfm by about 10%. Is that correct?

Alot of the LSX engine shops use the pipe also to flow exhaust ports. They claim it mimics the exhaust pulse as it leaves the port as it would when you have your headers installed.

They say it's to duplicate the header pipe. The % increase depends on the size and lenth of the pipe. Thats the deal. you can change the pipe size and see more airflow . Just another shell game

I just spent 2 weeks testing heads and intakes on the 500 EFI engines. I ran a set of Dart 310 Pro 1 right out of the box No Porting as cast and made 582 HP. Then I put a full cnc ported AFR 315 on with their special ex valves and made 12 more HP. I had the divider cut out of the intake plenum and the Bigger throttlebody on both times. I then put the Holley Intake on made 25 more HP but lost a ton of torque thru the whole RPM range. So I went back to the stock intake and mounted a 2000 cfm throttlebody right on the top of the stock plenum and made 35-40 HP and pick up the same on torque thru the whole RPM range. I should have my new Plenum tops ready in about 3-4 weeks.They will bolt right on your stock intakes and will flow over 2000 cfm. The 2 throttle blades are mounted right in the top flush so you don't need any more hatch height.

What heads were on when you pick up 35 or 40 hp

I had the AFR's on at that time but the Darts would have picked up some also. We just could not get enough air thru the 1300 cfm thottlebody.

New Plenum's should be nice! Thanks