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Speed Secrets: Cathedral vs Rectangular Port Cam For Your 408 Stroker Engine Cam Swap

What happens when you upgrade from a factory camshaft to an aftermarket cam when you do the swap on a 408 stroker engine? Digging even deeper, what happens when you upgrade to an LS3 rectangular port style camshaft, on a stroker that’s equipped with cathedral-port cylinder heads? Let’s find out if this combination will work!

When you look at the COMP Cams selection of camshafts, you’ll find a selection of cams made specifically for rectangular port heads, and cams designed specifically for cathedral-port heads. When mixed and matched together during testing for the Speed Secret series, a lot of the combinations work great. This episode explores the mashup prior discussed on the 408 stroker engine, using a test engine, and then throwing it up on the engine dyno to see what the results are. 

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To get the test engine up to par, it got a forged crank, forged rods, and forged pistons. The team also installed a set of ported cylinder heads, a FAST LSXRT intake manifold, and a 102mm throttle body. In addition to the intake and throttle body use, FAST also supplied the fuel injectors used, and a FAST XFI management system. 

Getting things moving on the dyno after the initial build, Speed Secrets used a factory 6.0-liter truck camshaft to get a baseline for the horsepower on the dyno. The results of the run with the stock cam was a 449-horsepower and 522 lbs-ft of torque result. 

Now swapping to a much healthier COMP Cams camshaft, the engine puts out 624-horsepower and 579 lbs-ft of torque – that’s a gain of 175-horsepower! Not only does this prove that running a stock camshaft in a built engine (or most any engine) is wasting a lot of horsepower, but mixing and matching the different style cams can actually create a really impressive result! 

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