I'm considering using AFR heads for a race 355 inch engine. My concern is if there's any potential left in the already CNC-ported AFR heads if I were to use them again on a larger inch engine in the future?

 

Not sure. You'd probably have to have a shop that REALLY knows what they're doing with port work. I've seen a few people try to improve their flow doing stuff that's familiar to most of us shadtree mechanics. Usually ended up in minimal improvement, or made the situation worse.

 

That's what I was figuring. Any flow work on the heads wouldn't be performed by me, rather by someone that knows what they're doing. Hopefully someone will glance at this who either has some information, or has tried to have their AFR heads improved. Maybe I can throw this question out for interpretation in a different way and try to get an answer to what the root of the question is. Say, for instance, I wanted an AFR head capable of 300 cfm of flow at 0.700" lift for use in the future on a 415 inch SBC in a drag racing environment with standard valvetrain hardware (non-offset). To achieve this, I would need an AFR 220cc head with the Competition prep. package, which flows 303 cfm @ 0.700". Now, say I'm building the 355 inch engine which would not need the 300 cfm @ 0.700" because the RPM range would not be that high to utilize such flow. So I buy the AFR 220cc head with the Race Ready 70% CNC port, which does not flow the 300 cfm, so obivously there's some potential left in a Race Ready AFR head. Now, with a runner of this size, will the 355 inch engine be a dog because of low port velocity? I've read that AFR is the leader of the pack when it comes to port velocity, but I was originally looking at a runner around 200cc for a 355 inch engine. I'm worried with the extra 20 cc's, port velocity will be down, and the car will be a dog. Any ideas?

 

I regularly put heads with runners that are "too big" on my engines. I currently have 200cc Dart Iron Eagles on a 355 with 9:1 compression, a tiny little cam and a stock stall converter. It gets with the program OK. 220cc....... might get a little doggy down low. But you can always keep velocity up the old fashioned way- with sheer RPMs! A little more stall in the coverter, a little more gear than you would normally use.... problem solved (or at least worked around semi-intelligently).

End of the day.... bottom end torque is far more influenced by the choice of cam than it is by intake runner size. Another alternative if you don't like the higher RPM range idea...... If the heads are too big, give it a cam that's a little small to prop up the bottom end some. Is it a mismatch? Sure, but you knew that going in. Big heads/small cam works a whole heck of a lot better than small heads/big cam. Good flowing heads will "stretch" the RPM range of a small cam beyond what you'd normally expect with lesser heads.

 

I don't have a definate answer to you question but I can tell you that my 195's have TONS of material left in them. I plan on having these ported when I do a big inch small block buildup.

 

I had my AFR are only 70% CNC'd and flowed 280cfm. The shop that flowd them for me were very impressed as this was their first set of AFR's through the door. I asked about getting more flow and he showed me some minute areas that could be massaged a little and pick up another 15-20 cfm easily. So the 210's are capible of going at least 300 cfm, the 220's should be a shoe in.

 

It seems like the 210's at this point would be the most suited to what I'm trying to accomplish. Motor is a 355 in., pump gas, 10-11:1, 0.645/0.630", 260/264*@0.050" solid roller, tunnel ram, 2 450 mech. sec., 4 speed, 4.88 gear, revving to 7k. Would the 220's be too overkill?

 

I'm very happy with my 210's and given what they flow, like you I plan on a 4??cid sbc in the future and am very confident they will still work flawlessly with my combination. If you were going to have a very high compression, big duration cam for all out tweak to the max performance in a straightline the 220's would be the better choice. But given what you have now, and what the future plans are, I dont think you will regret the 210's, defintely heads you can grow into. The 210's out flow Dart pro 1's 230's that have had minor porting and outflow all the factory BBC 781 heads and are right there with the 781 castings that have been worked to the max. That's how good these heads are.