COMP offered cam profiles designed for both rec-port and cathedral-port LS applications. Which one works best on a modified (Cathedral-port) LS2?

Words and Photos By: Richard Holdener

The power potential of LS motors is amazing. Right from the factory, the LS engine family was blessed with almost everything required to produce prodigious power. From displacement to the intake design to cylinder heads, LS engines were gifted an abundance of airflow. The only thing missing from the factory package (by design) was cam timing. In truth, the factory engineers never designed the stock LS motors for maximum power. Their needs were much more elaborate and constrained, having to meet emissions, longevity, and fuel mileage criteria, in addition to power production.

Having every aspect of performance covered BUT the camshaft meant your average LS (any LS) was literally begging for a cam swap. The question today is less of whether you should upgrade your cam, but which cam should you choose? The question becomes even more complicated when you consider the fact GM offered LS motors with no less than three different head configurations (cathedral-port, LS3 rec-port and LS7 raised rec-ports).

Those three different head configurations meant companies like COMP Cams were required to produce different cam families designed for each head configuration. You see, one of the variables that determine an effective cam profile is the relationship between the intake and exhaust flow of the cylinder heads. Generally speaking, the intake flow of an LS cylinder head is better than the exhaust flow. This is true for the cathedral-port, LS3 and LS7 applications. That the LS3 and LS7 offer so much more intake flow than a cathedral port, but similar exhaust flow, means the effective cam profile for the rec-port head will offer increased exhaust duration.

Taking a look at popular cams offered by COMP Cams, we see a typical intake-to-exhaust spread for cathedral-port applications is eight degrees, meaning the exhaust duration is 8 degrees greater than the intake. By contrast, the rec-port cams double that split, where the exhaust duration is 16 degrees greater than the intake. Given the same intake duration, our question was how would the rec-port cam, with more exhaust duration, work on a cathedral-port motor?

To test the rec-port cam, we decided to run it on the dyno against a comparable  cath-port cam, on our cathedral-port motor. The test motor started out life as a 6.0L LS2. After disassembly and machining, the LS2 was treated to a polished stock crank and Bullet series Carrillo rods and forged flat-top pistons. The forged short block was topped with a set of Stage 2 Total Engine Airflow 243 (LS2) heads (that flowed 320 cfm), an MSD Atomic intake, and 105mm Holley throttle body.

Of course, the cams were the star of the show for this test, and we chose two grinds that were ideally suited for the 6.0L. The 54-459-11 cathedral-port cam offered a .617/.624 lift split, a 231/239-degree duration split, and 113-degree lsa. Note the 8-degree split between the intake and exhaust duration. Representing the rec-port crowd, the 54-469-11 cam featured the same .617/.624 lift split and 113-degree lsa, but differed in duration with a 231/247-degree split. Basically, the difference between the two cams was the increased exhaust duration offered by the 469 rec-port cam.

To compare the two cams, we ran the modified 6.0L on the engine dyno at Westech Performance. The LS2 was configured with a set of long-tube Hooker headers (with collector extensions), a Meziere electric water pump, and (most importantly) a FAST XFI management system to dial in the all-important air/fuel and timing curves.

The LS2 was first equipped with the 459 cam. After dialing in the air/fuel and timing curves, the 6.0L produced peak numbers of 553 hp at 6,700 rpm and 483 lb-ft of torque at 5,200 rpm. The torque production exceeded 450 lb-ft from 4,100 rpm to 6,400 rpm, making for a broad, usable torque curve.

The cam swap netted interesting results on the dyno. Equipped with the 459 (cath-port) cam, the 6.0L produced 553 hp and 483 lb-ft of torque. Run with the 469 (rec-port) cam, the LS2 produced 560 hp and 481 lb-ft of torque. The rec-port cam offered slightly more peak power but lost torque production below 5,200 rpm. Both of the COMP cams offered impressive power curves, you just need to decide where power production is most important.

After installation of the rec-port 469 cam, peak horsepower production was up to 560 hp at 6,700 rpm, but the peak torque dropped by two lb-ft to 481 lb-ft at 5,400 rpm. The 469 cam also offered a broad torque curve, but torque production suffered slightly below 5,200 rpm compared to the 459 (cath-port) cam.

To complete our cam conundrum, we now need to run this cam comparison on a rec-port LS3, to see if the trend stays consistent. Either way, COMP has a cam to fit your LS needs, even if you decide to mix and match the cathedral-port and rec-port cams and motors.

Rec vs Cath-Port Cam Test-Comp 459 vs 469 (Mod LS2)
The LS2 test motor featured a forged rotating assembly from CP/Carrillo stuffed inside the aluminum LS2 block. The modified LS2 was topped with TEA-ported 243 heads and an MSD Atomic intake. The 47-pound Accel injectors were dialed in using a FAST XFI management system. Equipped with the 54-459-11 (cath-port) cam, the LS2 produced 553 hp at 6,700 rpm and 483 lb-ft of torque at 5,200 rpm. After swapping in the rec-port 54-469-11 cam, the peak numbers changed to 560 hp at 6,700 rpm and 481 lb-ft of torque at 5,400 rpm. The increased exhaust duration offered by the rec-port cam increased power higher in the rev range but dropped torque production slightly below 5,200 rpm.

Sources: ARP, Arp-bolts.com; COMP Cams, compcams.com; CP Pistons/Carrillo Rods, Cp-carillo.com; FAST, fuelairspark.com; Holley/Hooker, holley.com; MSD, Msdignition.com; Total Engine Airflow, totalengineairflow.com