AFR Head Advice, compression and stuff
11-10-2006, 08:04 PM
#1
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Join Date: May 2003
Location: Prince George B.C. Canada
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AFR Head Advice, compression and stuff
Hey guys I'am going to be ordering up a set of those new AFR Eliminator heads in 195cc with straight plugs now just want to get your thoughts on which version of the head the 65cc or the 75cc ones. From what I figured the 65cc ones will give me a 9.0:1 compression and the 75 would be about 8.2:1. Is there any advantage to going with the 75cc head on like a 5.7L motor after I blow this one for rebuild options? Would 8.2:1 compression be a major dog for street driving all though it might be safer with the current stock motor? I'll be changing the cam to a ZZ9 one if that helps at all and will be sticking with the SS runner TPI intake.
11-12-2006, 10:54 AM
#2
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Location: wilmington, NC USA
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well.. there are a few tranes of thought on this decision. the new AFR heads are going to have much better designed chambers for fast burn so compression can be raised a little bit and timing backed down to make the same power.
on the other hand.. more boost can be had safely with a lower compression ratio and pump gas.. but unless you plan on building your fuel system beyond what I see in your signature, you won't be running all that much boost before maxing out the injectors and likely pump. So the smaller chamber heads will net more power at lower boost pressures.
just kinda up in the air with where you want to take this project. for all out racing lower compression and more boost and more fuel will be stronger.. if its a street machine, lower boost, higher compression will be more street friendly.
also being a blower car with pressure pent up behind the throttle blade even at idle.. go ahead and grab a larger set of heads then the 195cc series.. the 210-215 would be a much better idea.. you don't need smaller ports for velocity, you have a blower for that.. you want the least amount of restriction between the compressor blades and the pistong tops to get the most out of the air the blower is trying to move.. think efficiency!!
choose a path and order accordingly.
Chris
on the other hand.. more boost can be had safely with a lower compression ratio and pump gas.. but unless you plan on building your fuel system beyond what I see in your signature, you won't be running all that much boost before maxing out the injectors and likely pump. So the smaller chamber heads will net more power at lower boost pressures.
just kinda up in the air with where you want to take this project. for all out racing lower compression and more boost and more fuel will be stronger.. if its a street machine, lower boost, higher compression will be more street friendly.
also being a blower car with pressure pent up behind the throttle blade even at idle.. go ahead and grab a larger set of heads then the 195cc series.. the 210-215 would be a much better idea.. you don't need smaller ports for velocity, you have a blower for that.. you want the least amount of restriction between the compressor blades and the pistong tops to get the most out of the air the blower is trying to move.. think efficiency!!
choose a path and order accordingly.
Chris
Last edited by NC-LT1; 11-12-2006 at 10:57 AM.
11-12-2006, 11:45 AM
#3
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Join Date: May 2003
Location: Prince George B.C. Canada
Posts: 65
The fuel pump has be replaced with a 255LPH pump and if the current injectors give me any problems I'll swap them out for the Motron 60 lb/hr injector, I hear they idle better to anyways.
I think I might go with the with the lower compression and see what kind of street manners it will have, boost with current pulley is 10PSI at 5500 so losing some HP and gaining some safety might not be a bad thing with the stock short block. Then it will give me a idea as to how I want to go with the rebuild.
Not sure if I would want to go with the 210-215 head all though you do bring up some good points. The new AFR 195 flow as good as there older 210's so I'am thinking they should be good enough for the HP I want and if not there not hard to sell.
Thanks for the reply.
I think I might go with the with the lower compression and see what kind of street manners it will have, boost with current pulley is 10PSI at 5500 so losing some HP and gaining some safety might not be a bad thing with the stock short block. Then it will give me a idea as to how I want to go with the rebuild.
Not sure if I would want to go with the 210-215 head all though you do bring up some good points. The new AFR 195 flow as good as there older 210's so I'am thinking they should be good enough for the HP I want and if not there not hard to sell.
Thanks for the reply.
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