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Intake Runner Improvements

Improving flow with the constraint of retaining the same intake runner volume only leaves one option: change how the air moves through the
runner. The objective is to get more air through effectively the same physical area. To do this AFR reshaped the roof of the intake runner and cleaned up how it transitions around the valve guide boss. Compared to

The AFR165cc Comp porting package features reshaped intake bowl and guide areas.
the standard AFR 165cc head, a glance down the new intake port reveals a much longer "air foil" taper along the roof leading up to the guide. The tear drop shape around the guide itself is more aggressive, and the wing shape runs past the back side of the guide leading into the long-side radius. Also improved is the short side radius. The turn is laid back resulting in less turbulence and a straighter shot into the bowl area. All told the changes to both the intake and exhaust side add an additional hour-and-a-half to the normally two hours it takes to complete the standard 165cc head. The increased CNC time is also a result of finer cutting levels and less tool deflection. Anyone who is familar with AFR heads has seen the concentric ridges throughout the runners. On the Comp package heads these ridges are less pronounced.

The result (see Chart 1) of the additional CNC porting is valuable flow gain in the .400-.600 thousandths valve lift range. The standard 165cc head hits flatline at exactly half-inch lift. While this was fine for stock or mild cam applications, it put street guys wanting the low to mid .500" lift cams in a predicament. Many aftermarket 5.0L cams are ground with over .500" lift but conservative duration numbers to keep the EFI computer happy. These aren't high reving motors and if a guy steps up to the AFR 185cc head he may struggle with the low end torque loss due to the large runner volume. With the Comp package head we get the flow above .500" and there is even an improvement at the low lift points. The average flow between .200 to .500" lift calculates to 201.5 cfm which heartily beats our results of the Trick Flow Twisted Wedge head, which previously edged out the standard AFR 165cc head 199 cfm to 194 cfm Even more remarkable is this is still done with stock-piston friendly 1.90" intake valve.

Greater Exhaust Flow


Competition package exhaust port.

Standard 165cc exhaust port.
The first impression the Comp head makes is its' square exhaust ports. This is straight out of Tony Mamo's playbook, and a bold departure from the hallmark D-hole exhaust port on the standard head. The pressure of the exiting gasses forces flow against the roof. By raising the port ceiling and opening up the area around the guide, turbulence is reduced and the chamber is evacuated faster. Also contibuting to the gains are enhancements to the valve job for the Comp package 165 head. All told the flow gains are huge. From just .200" lift the head is flowing 10% better than the standard predecessor. Keep in mind that the 185cc older brother shares the same exact exhaust runner as the 165cc head. It is rumored that eventually the 185 will also be offered with a Comp package, but for now this means the 165cc Comp exhaust port will outshine that of the 185cc head. This puts the head in interesting territory for forced induction and nitrous motors. Considering that many 5.0L enthusiasts are shopping for emmisions compliant parts, including blowers, the 165cc Comp head with its big exhaust flow is a great option. It is emmisions legal, wont require piston notching for guys sticking with mild cams, and the 79-80% exhaust-to-intake flow ratio is ideal for purging the big boost volumes from the combustion area.

The Bottom Line
AFR heads have never been the cheapest heads on the market, but they are likely the best engineered. The standard 165cc head retails at around $1300, putting it a couple hundred above its major competitors. The Competition porting package adds another $300 to the ticket. A $1600 expenditure on a set of small block Ford heads is pricey, but consider that many guys eventually exceed that cost by sending out an inferior aluminum head for porting to get the flow numbers into respectable range. We've done it ourselves. AFR anticipates this head will be a hit amongst guys who are not willing to leave any power on the table. We believe it will also be a popular choice for those of you building 302 to 331 cid motors looking for broad, table flat, torque curves and yet good peak horsepower in the 6000 rpm range. Either way it is surely a solid investment that will be tough to beat for a long time time to come.

We have yet to see live results with this head due to its newness, but some early engine dyno testing performed by AFR on a mild dual-plane 302 motor showed 8-10 horsepower across the board over the standard 165 head. The intake manifold was noted to be potential choke point with the new Comp heads, and porting or at least port matching the intake to the heads will be highly recommended to take advantage of the flow potential. We will conduct our own comparision in the near future, look for an article soon.
 
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Rob Jr. from Rob's Auto Machine in Hayward, CA get' the new AFR 165cc head mounted on the flow bench. Heads were flowed at a standard pressure of 28" H20, using a 4.030" bore fixture. A radiused inlet was used on the intake port, while no exhaust tube was used. An exhaust tube, used to simulate a header, would have increased the flow numbers by several cfm.

 





















Flow Bench Results
Intake Flow @ 28" H20
lift (in.)
Std. 165
165 Comp
.100
60
63
.200
125
132
.300
188
191
.400
226
235
.500
238
248
.600
248
258




























Flow Bench Results
Exhaust Flow @ 28" H20
lift (in.)
Std. 165
165 Comp
.100
52
54
.200
100
111
.300
142
156
.400
168
187
.500
181
199
.600
189
201















Sources
Air Flow Research Heads
10490 Illex Avenue
Pacoima, CA 91331-3137
818-890-0616
Rob's Auto Machine
Industrial Blvd.
Hayward, CA
510-732 1909

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