Text and Photos by Chirag Asaravala

As editors of a tech magazine we're often pursuing story ideas where we pit one product against another. In many cases we know with a good deal of certainty what the outcome will be even before we dyno or track test the products in question. Yet we still run the tests in a fair and scientific manner so that we can convey the results to you and those who may genuinely want to make a buying decision on factual information. Every so often, however, we come across products for which we are just as curious as you are as to what the outcome will be. Such was the case with AFR's new Competition 165cc head for small block Fords.

The 165cc Comp head is a derivative of their existing, and immensely popular, 165cc head. The difference is that the Comp head receives additional CNC port work, a result of an extensive R&D efforts last year by AFR to improve the port design while maintaining the runner volume. The result, in addition to flow gains, should be phenomenal velocity that yields more torque and horsepower over the standard head. Exactly how much more is what we're about to find out.

Test Mule

The objective is rather simple - bolt the standard 165's on a motor and dyno it. Pull them off and bolt the Comps on and dyno again. This is all to be done on the same day, under the same test conditions, to get an accurate comparison. The original plan was to bolt these heads onto our Project '93 Cobra. It made sense since that car had received a set of standard 165's and put down over 300 horse to the wheels. The only glitch was that the car was stolen shortly afterwards. Without a project car and a set of standard 165cc heads to baseline with, we had to draw up the plans all over again. Things started to come together when we were flow testing the heads at Rob's Auto Machine in Hayward, CA. Rob's had expressed interest in proving the merits of their popular 347 short block on the dyno. Over the next month they machined and assembled their stout stroker motor with goods from Eagle, JE and ARP while we rounded up the rest of the combo with various parts from projects past and present; such as the Crane solid roller setup from our 400HP302 project and a trusty Weiand X-CELerator manifold. A fresh set of standard 58cc AFR 165's were also procured and setup with 1.6:1 roller rockers.

We're certain at this point many of you are wondering why we'd put 165cc heads on a 347. The answer is we probably wouldn't. However because the 165cc Comps flow darn near the 185's with a smaller runner and intake valve, we thought it'd be interesting to see what sort of torque this motor produces. Besides, the point of the test is to observe the differences between the two sets of heads. The actual displacement used is inconsequential to this effort.

Dyno Time
Once assembled and primed the 347 was hauled off to Dave's Engine in Newark, CA to be loaded up on their Superflow engine dynamometer. As Dave is quick to point out, the $50,000 dyno (plus another $50,000 spent on building the dyno room) is "like owning a race car without wheels." The engine has to be delivered the day prior to the test day so it can be loaded up on the stand, starter, headers and bellhousing connected, fuel and water plumbed, and then started to check for leaks and pressures. Set up is an all day affair, and if the engine checks out ok you've won half the battle. The myriad of sensors on the dyno are all apt to their own nuances and require maintenance, just as they would if in a vehicle. The highly sophisticated dyno monitors for every parameter you can imagine. During our session we kept an eye on exhaust, coolant, oil, and air temps; air-fuel ratios; brake-specific fuel consumption; and airflow into the carburetor, to name a few.

With the motor successfully installed and started to check for leaks, we were ready to roll, bright and early the next morning. The first couple hours on dyno-day entail more system checks followed by initial tuning then ring-seat time as this was a fresh motor. After successful break-in we adjusted timing to 34° and then worked on getting air-fuel ratios optimized. Our Barry Grant Speed Demon 650 required an increase of jet sizes in both the primary and secondary metering blocks. This yielded air-fuel ratios between 13.5 and 13.9:1 at wide open throttle. While this may seem a tad lean, Dave's experience has been that Demon's run better at these ratios. This proved to be true as we observed a loss in power with any fatter jetting.

With timing and fuel properly set we started making pulls for the books. The first set of pulls were made with the standard AFR 165 heads. The motor belted out 440 horsepower at 6250 rpm and 418 lb-ft of torque at 4300 rpm. What is stunning is the table-flat torque curve from 3500 rpm to 5500 which maintains over 400 lb-ft of torque. While we weren't quite at the horsepower levels we thought we'd see, torque was a pleasant surprise. With the standard heads setting the baseline, it was time to get the Comps bolted on.

How to perform a head swap on your lunch break
With dyno room costs at over $600 a day we weren't exactly taking our sweet old time during this test session. We wanted to wrap up in a day and that meant staying on schedule to the minute. When Tech Editor Langley called in sick the night before it meant I'd be flying solo on the head swap. The clock showed 11:30am after the last pull was made with the standard AFR 165 heads. That's when I started wrenching away to get the 165 Comp heads on. With some help from Rob at Rob's Auto Machine, we were ready for round two by 1:30pm. Granted, dealing with a motor on an engine stand is a whole lot easier than when in a car, this was still a chore. In case you ever want to try to beat our time, the chronology is below. Continue

11:30am - The mad dash starts immediately after the last AFR 165 pull. Gloves are necessary to remove scorching hot headers and rockers.

11:55am - Back out a dozen bolts and the manifold and carb are removed as a unit. Distributor stays to avoid re-timing.

12:10pm - An electric impact wrench makes for quick head bolt removal. Drain the block first to avoid a coolant mess and a very ticked off dyno owner.

12:30pm - After scraping and cleaning the deck, new head gaskets (Fel Pro 8548PT2) are layed down. This is no time to forget about the "FRONT" stamped in the gasket.

12:35pm - The AFR 165 Comps are aligned over the dowels and then the headbolts (reused) are torqued to spec in the usual crisscross pattern.

1:30pm - The rockers are lashed to spec, headers and intake bolted back on, and valve covers, plugs, wires replaced. Final operation is an oil and filter change.

(165cc Comp Head gets tested)

In This Article:
AFR has raised the bar for aftermarket small block Ford heads with the introduction of the 165cc "Competition Porting package." The part number #1404 head benefits from an enhanced CNC porting program over the original 165cc head. We pit both heads against each other on our Rob's Machine 347 small block.

Also See:
Solid Investment: AFR 165cc Comp. Testing AFR's 165cc Heads

Our flow testing showed the extended CNC work on the 165cc Comp head (above) to be worth an average of 10 cfm on the intake side and nearly twice that on the exhast over the standard 165cc head (below).
Both of the 165cc models we tested featured 58cc combustion chamber volumes, 7/16" studs, and upgraded dual-roller valve springs. All 165cc heads come with 1.90"/1.60" valve sizing.

The 347 motor was assembled by Rob's Auto Machine of Hayward, Ca. The short block is their own bullet-proof recipee consisting of Eagle forged steel crank and H-beam rods, coated SRP pistons, and coated bearings - all properly neutral-balanced.

To ensure smooth operation on the dyno we opted for this Professional Products SFI approved harmonic balancer which features removable counter-weights (makes the neutral-balance issue real easy to resolve.) The pulley spacer helps with V-belt or late-model serpentine pulley options.
347 Engine Specs - As Tested
Block Stock 5.0L (Zero Decked)
Crank Eagle 4340 Forged 3.400"
Rods Eagle 4340 H-beam
Pistons SRP +.030" (coated)
Rings Total Seal
Bearings Clevite (coated)
Oil Pump Melling M68
Timing Billet 9-keyway
Balancer Professional Products SFI (neutral balance)
Fasteners ARP
Camshaft Crane S238 solid roller
(238/246 .560"/.579")
Lifters Crane Pro Series
Solid Roller
Intake Weiand X-CELerator
Heads AFR 165 or 165 Comp.
58cc (10.5 1 comp.)
Carb Speed Demon 650cfm
Rockers Scorpion 1.6:1
Pushrods Comp Cams


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