Air Flow Research is one of the go-to companies for aftermarket cylinder heads and for good reason, as AFR products have always produced impressive results. When we had the opportunity to test AFR’s LS3 Mongoose cylinder heads, we jumped at the chance.
The AFR Mongoose LS3 12-degree cylinder head is a rectangle port design that is 100-percent machined on the company’s 5-axis CNC equipment. They are cast in A356 aluminum and feature the highest quality components, such as titanium retainers and PAC valve springs, with further upgrades available. The heads are CARB-certified and emissions legal for 2007-2016 6.2-liter LS3 engines, too, so if you feel your Camaro is ready for a bump in power output, these are ready for you and will still pass inspection.
Equipped with a 260cc intake runner volume and 95 cc exhaust runner volume, the LS3 Mongoose cylinder heads require a minimum bore size of 4.000-inch to clear the 2.165 intake/1.600-inch exhaust valves, and they are intended to be used on engine applications up to 454 ci and with a rev range of 7,000 rpm. Combustion chamber size comes in at 69cc and the heads are available in 4- and 6-bolt per cylinder fitments.
While our test engine is on the smaller side of this cylinder head’s capabilities, you’ll see it still offered a noticeable improvement over stock heads, and they are ready for the next step in this engine’s evolution.
Our subject test engine is a 408ci stroker based on a Gen III 6.0-liter iron truck block. It features a 4.030-inch bore size and a 4-inch stroke and was machined by United Speed World of Tampa, Florida, and assembled by Greg Lovell of Antivenom in Seffner, Florida. The rotating assembly consists of 6.125-inch Eagle H-beam connecting rods, an Eagle crankshaft, and Wiseco pistons with +6 cc dome.
Our baseline cylinder heads are stock LS3 castings with a Brian Tooley Racing upgraded valve spring package good for .660-inch of valve lift, and the compression ratio checked in at 10.5:1. To facilitate dyno testing, the dyno runs were performed using a carbureted induction package that consisted of a Quick Fuel Technologies 750cfm carburetor, a Mast Motorsports 2-piece intake manifold, and a Daytona Sensors Smart Spark for the ignition.
After bolting the engine to United Speed World’s Superflow dynamometer, a set of 1 ¾-inch primary long-tube headers were fastened up, and the LS powerplant was fed a mix of 100-octane race fuel and pump gas. We ran the engine in this configuration to establish our baseline numbers, and then bolted the Air Flow Research Mongoose 260 heads on. After that comparison, we also tried out a larger 850cfm carburetor and carb spacer that United Speed World keeps in the dyno room. The combo has proven to be a reliable performer on numerous other engine builds, and it didn’t disappoint here, either. Check out the photos and captions to see the results.
Air Flow Research
Brian Tooley Racing
Eagle Specialty Products Inc.
Quick Fuel Technology
United Speed World