Questions concerning milling AFR's...
02-28-2005, 04:57 PM
#1
Questions concerning milling AFR's... Seems I get a few questions a week concerning milling AFR heads....how much is OK....will it hurt flow, etc. etc.
As I have stated earlier in a few other threads, milling our heads for higher compression does have a negative effect on head flow, but only when the mill becomes "excessive"....Note my response to a private message I received earlier inquiring about this exact situation. I thought it was good information that would help everyone out and save me from answering everyone on a "one on one" basis long term.
[QUOTE]
Conservatively milling our heads for more CR doesn't pose a problem. A good rule of thumb is to try not and take much more than .035 off the deck....once you exceed that figure you can see the flow numbers start getting softer fairly quickly (kind of looks like an "X squared" curve if you were to plot mill amount versus flow losses). Up to .030 is safe...even .035 isnt bad, but start pushing it much past .040 and you start to offset the gains in CR by the loss of headflow. A better situation at that point would have been a different piston design that had more positive dome volume...be it a flat-top versus a dish, or a small "pop-up" versus a flat-top etc.....any situation that would allow for the same CR without having to mill .040 + off the deck. Then you would have all the benefits of the higher compression without any of the downside side-effects of the loss in headflow.
[QUOTE]
Don't forget guys....use .006 per cc to figure out what you need to achieve the correct chamber volume...this way you can figure whether a different piston configuration might be better than another to help you get to the final compression ratio you are shooting for.
Thanks,
Tony
As I have stated earlier in a few other threads, milling our heads for higher compression does have a negative effect on head flow, but only when the mill becomes "excessive"....Note my response to a private message I received earlier inquiring about this exact situation. I thought it was good information that would help everyone out and save me from answering everyone on a "one on one" basis long term.
[QUOTE]
Conservatively milling our heads for more CR doesn't pose a problem. A good rule of thumb is to try not and take much more than .035 off the deck....once you exceed that figure you can see the flow numbers start getting softer fairly quickly (kind of looks like an "X squared" curve if you were to plot mill amount versus flow losses). Up to .030 is safe...even .035 isnt bad, but start pushing it much past .040 and you start to offset the gains in CR by the loss of headflow. A better situation at that point would have been a different piston design that had more positive dome volume...be it a flat-top versus a dish, or a small "pop-up" versus a flat-top etc.....any situation that would allow for the same CR without having to mill .040 + off the deck. Then you would have all the benefits of the higher compression without any of the downside side-effects of the loss in headflow.
[QUOTE]
Don't forget guys....use .006 per cc to figure out what you need to achieve the correct chamber volume...this way you can figure whether a different piston configuration might be better than another to help you get to the final compression ratio you are shooting for.
Thanks,
Tony
02-28-2005, 07:43 PM
#3
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Thanks Tony for letting everyone know this!! We have been milling a few sets of AFR's for customers, & Dave was quick to give me a heads up on this back when we first started recieving heads.
Just wanted to let everyone know we have AFR heads eather in stock or on the way!! I have 225's ready to ship & 205's will be in in about a week. PM, email or call me for pricing!!
Just wanted to let everyone know we have AFR heads eather in stock or on the way!! I have 225's ready to ship & 205's will be in in about a week. PM, email or call me for pricing!!
