afr numbers
Thread Starter
Team Owner
Joined: Nov 2004
Posts: 20,715
Likes: 25
From: Sorrento Italy
afr numbers
i hope you'll pardon my ignorance 
...but what does it mean heads beeing 180/210/220 cc...i have alu afr heads 210 cnc ported, is it the capacity in cc of the combustion chamber and then of the engine compression...? so it means the bigger the number the less the compression, am i right? or maybe i'm totally wrong? 
...but what does it mean heads beeing 180/210/220 cc...i have alu afr heads 210 cnc ported, is it the capacity in cc of the combustion chamber and then of the engine compression...? so it means the bigger the number the less the compression, am i right? or maybe i'm totally wrong?
Race Director
Joined: Jun 2000
Posts: 10,046
Likes: 675
From: FL
Totally wrong. 
Basically, there are two numbers.
Chamber size is usually 64 or 76 cc for small blocks. Occasionally 58 cc. This will determine your compresson ration.
Intake port size determines how much air the head can flow which directly relates to HP potential. A lot of manufactuers use this nmber to describe their heads. So a 195 head has a smaller port than a 210 cc head.
Now, here is the kicker. Different heads flow better than others. A 195 cc AFR head will flow enough for a 406 ci engine. As long as the head can flow enough air to support the engine, a smaller port volume is generally considered better. Why? Because a smaller port will have a greater velocity to flow the same amount of air as a larger port. This tends to improve torque and part throttle response over the larger (and slower) port.
Hopefully, I have confused you too much.
Basically, there are two numbers.
Chamber size is usually 64 or 76 cc for small blocks. Occasionally 58 cc. This will determine your compresson ration.
Intake port size determines how much air the head can flow which directly relates to HP potential. A lot of manufactuers use this nmber to describe their heads. So a 195 head has a smaller port than a 210 cc head.
Now, here is the kicker. Different heads flow better than others. A 195 cc AFR head will flow enough for a 406 ci engine. As long as the head can flow enough air to support the engine, a smaller port volume is generally considered better. Why? Because a smaller port will have a greater velocity to flow the same amount of air as a larger port. This tends to improve torque and part throttle response over the larger (and slower) port.
Hopefully, I have confused you too much.
