The small-block Ford cylinder head market is flooded with options ranging from 160cc intake runners all the way to huge 240cc high-port race heads and everything in between. But bigger is not always better, especially for a street-driven Stang. The size of the intake runner dictates air velocity, and the smaller displacement an engine has, the less velocity the incoming air will have when using larger intake runner cylinder heads, especially at low rpm.
So what size cylinder heads should you choose? Well, the ideal scenario would be to have the increased runner velocity of a smaller intake runner while still being able to flow a large volume of air like larger intake runners. But you can't have your cake and eat it too, right? Maybe you can.
Airflow Research, known simply as AFR, recently revamped its entire SBF cylinder head line. The new versions, which have taken the place of the old line, are simply called: Renegade. Not to take anything away from the old AFR heads--these are simply in a different league than the elder versions. Utilizing the same part numbers and even price of their predecessors, the new versions are anything but re-massaged touch-ups of the old heads.

Airflow Research's new 165cc...

Airflow Research's new 165cc Renegade cylinder heads (PN 1399; $1,560) are the latest iteration for the cylinder head giant.

1 Along with the heads, we...

1 Along with the heads, we ordered a custom cam from Comp Cams, as well as rockers, lifters, and pushrods. ARP sent us a set of head bolts, and Fel-Pro sent us all the gaskets we needed (not shown).

2 The new Renegade heads...

2 The new Renegade heads feature a 3/4-inch-thick deck to handle high cylinder pressures.
"The new SBF program is a clean-sheet deal. Improvements were made everywhere" says Tony Mamo of AFR, who is the head of R&D and designed these new pieces. "And we've been working on the new Renegade stuff for over a year and a half." This is where the cake-eating begins. Grab the ice cream. "Our focus was to improve the efficiency of the previous Outlaw version, which even today are still at the top of the performance food chain" Mamo told us. "Through an extensive effort, we managed to improve flow on the Renegade line on average about 15-20 cfm. That's a huge improvement in airflow, one that leaves our 165 Renegade flowing similar to the 185 Outlaw, the 185 Renegade flowing similar to the 205 Outlaw, and so on.
"An added benefit being the obvious increase in air speed through the better shape port/chamber configuration needed to accomplish this, which improves air charge inertia and cylinder packing. It also helps reduce the negative effects of reversion from overlap in performance camshafts. It's a win-win design philosophy and these new heads should really pack a punch for the end user," Mamo told us.

3a They also come with lightweight...

3a They also come with lightweight 1.90/1.60-inch valves, 1.290-inch-OD valvesprings, 3/8-inch ARP rocker studs, and 5/16-inch guideplates.

3b We opted for the $100...

3b We opted for the $100 titanium spring retainer upgrade.

4 The CNC combustion chambers...

4 The CNC combustion chambers are 58cc standard, but AFR milled ours to 50cc to bump our compression to 10.25:1.
But to be sure this just isn't some clever marketing ploy dreamed up deep in a conference room, we put a pair to the test. Our subject: a mostly-stock five-speed '90 LX hatch owned by James Bickam of Orlando, Florida. Bickam's super-clean Fox already had a handful of bolt-ons, including underdrive pulleys, shorty headers, a catted H-style mid-pipe, a Magnaflow after-cat, Cobra intake and matching 65mm throttle body, C&L elbow and 73mm MAF, and a high-flow air filter in the stock airbox (silencer removed). Other than that, it has subframe connectors, 3.55 gears, and some performance springs, shocks, and struts. Heck, it's still rockin' the clutch fan.
Since we were dealing with a stock short-block, we knew that we needed heads with smaller intake runners, but weren't sure exactly which ones would maximize the potential of our 302. So we called Mamo himself for some guidance. He told us that our stock engine in naturally aspirated form would best utilize the 165cc versions. He also suggested a camshaft profile, which we passed on to Comp Cams for a custom grind.
Mamo suggested a 0.556/0.556-inch lift camshaft with 224/224 degrees of duration at 0.050-inch lift and a 112-degree lobe separation. Comp Cams ground the cam (PN 35-000-8; $297.78), and also sent us a set of aluminum roller rocker arms (PN 19044-16; $309.38), lifters (PN 851-16; $217.63), and hardened pushrods (PN 7619-16; $116.42). We also ordered a complete gasket set from Fel-Pro and fasteners from ARP.

5 Intake runners are CNC-ported...

5 Intake runners are CNC-ported and are 165 cc in volume.

6 Exhaust ports are 70cc...

6 Exhaust ports are 70cc and are designed to handle NA, turbocharged, supercharged, or nitrous applications.

7 At Auto Performance Engines,...

7 At Auto Performance Engines, the new Renegade 165s flowed as well as old AFR 185s.

8 Comp Cams sent us a custom...

8 Comp Cams sent us a custom camshaft, which features 0.556/0.556-inch lift, 224/224 degrees of duration, and a 112-degree lobe separation. Comp also sent us aluminum 1.6 rockers, hardened pushrods, and hydraulic lifters.

9 After a baseline pull on...

9 After a baseline pull on the Dynojet at Lamotta Performance in Longwood, Florida, tech Billy Eldert stripped all the stock stuff off James Bickam's '90 LX hatch, cleaned the surfaces, and installed the new camshaft.

10 He then installed the...

10 He then installed the new Comp Cams timing chain.
Our non-emissions 165cc heads (PN 1399; $1,560) feature 1.90/1.60-inch valves, fully CNC-ported combustion chambers and ports, 3/8-inch ARP rocker studs, and 5/16-inch pushrod guide plates. We did opt for titanium spring retainers, a $100 option. AFR also milled our heads down, bumping up our compression ratio from stock (about 9.2:1) to 10.25:1. The combustion chambers are usually 58cc on these, but ours are now 50cc. Since these were an all-new design, we wanted to see how they flowed on a flow bench. So we headed to Auto Performance Engines (APE) in Auburndale, Florida. There, Kevin Willis put the new 165s to the test. On a 4.030-inch bore on a Flow Pro bench, they flowed an astonishing 269.4/212.5 cfm at 0.500-inch and 278.5/216.9 cfm (intake/exhaust) at 0.600-inch lift! The intake flows over 200 cfm from 0.300-inch lift and above.
Willis was very surprised, and compared these to a pair of the previous AFR 185s that he tested, which flowed slightly better down low, but were surpassed by the Renegade 165s above 0.400-inch lift. He even had to re-check everything to make sure he did it correctly. For the install, we headed to Lamotta Performance in Longwood, Florida. There, Billy Eldert has been slowly modding Bickam's LX since the late '90s. To establish a baseline, we strapped it to Lamotta's Dynojet chassis dyno. It put down 222 rwhp and 272 lb-ft of torque.

11 The lifters were then...

11 The lifters were then lubricated and installed in the stock location.

12 Once the timing cover...

12 Once the timing cover and balancer were back on, Eldert aligned the timing pointer to TDC.

13 With the head gasket in...

13 With the head gasket in place, Eldert then mocked up one cylinder head to check piston-to-valve clearance.
Eldert installed the cam and a new timing chain from Comp Cams. He then mocked up one cylinder head and checked piston-to-valve clearance. Everything checked out, and he finished reinstalling the rest of the components and added five quarts of Comp Cams Muscle Car and Street Rod oil. He also set the timing back to 10 degrees BTDC, where it was when we started.
Back on the chassis dyno, without any additional tuning, Bickam's LX spun the rollers. It made 285 rwhp and 309 lb-ft of torque--a 63hp and 37-lb-ft increase. Eldert then installed an SCT Performance chip with a canned tune from SCT. After making another pull, we were rewarded with 302 rwhp and 325 lb-ft of torque. We picked up 80 rwhp and 53 lb-ft of torque with a heads and cam swap--and we didn't sacrifice any power or torque down low. You actually can have your cake and eat it too, after all.

14 Using toy clay, Eldert...

14 Using toy clay, Eldert determined that there was enough clearance, so he proceeded.

15 He then fastened the cylinder...

15 He then fastened the cylinder heads using the ARP head bolts.

16 He then checked the lower...

16 He then checked the lower intake gaskets to make sure the intake port holes were large enough for the heads.

17 He then reinstalled the...

17 He then reinstalled the lower intake.

18 Using a pushrod length-checking...

18 Using a pushrod length-checking tool, Eldert marked the valve stem with paint and turned the engine over by hand. Once the pattern is in the center of the stem, he knew he had reached the correct length.

19 He then installed the...

19 He then installed the Comp hardened pushrods and aluminum rocker arms.

20 He then reinstalled the...

20 He then reinstalled the rest of the components.

21 Eldert then set the timing...

21 Eldert then set the timing at 10 degrees BTDC, where it was before.

22 As you can see, this is...

22 As you can see, this is a minor bolt-on Fox: Cobra intake, C&L elbow and MAF, shorty headers, catted mid-pipe, an after-cat system, and underdrive pulleys. It even still has the clutch fan.

23a Eldert installed an SCT...

23a Eldert installed an SCT Performance chip...

23b ...to maximize the power...

23b...to maximize the power potential of our new combination.

24 Though we had traction...

24 Though we had traction issues with the street tires and didn't get a good e.t., quarter-mile trap speed was up 10 mph, from 95 to 105 mph--and we didn't sacrifice any driveability.
On the dyno, Bickam's LX made 302 rwhp and 325 lb-ft of torque--up 80 hp and 53 lb-ft of torque from a heads and camshaft swap!