Marc Christ
Brand Manager, Modified Mustangs & Fords
August 19, 2012

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.

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"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.

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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.

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