By Richard Holdener/Photos By Author
Do LS stroker combos respond to wilder cam timing?
The camshaft is one of the key components in the success of any LS build. Even if you have a serious stroker with the best flowing heads and the hottest intake, they can’t be expected to provide optimum performance without the right cam timing. To provide maximum performance, all of the individual components must work together in harmony. No single individual component cam make the combination successful, but just one wrong component can ruin an otherwise good one.
When you stop and think about it, the success of the combo comes even before choosing all of the individual parts. To get things started on the right track, you must first understand and clarify the intended usage for the motor. Certainly, a build up designed for an all-out, drag-race application will be different than for a tow rig or other daily driver. Only through a careful examination of the requirements can we select the proper components.
When choosing components for your build up, there are a number of potential pitfalls, the most common one involves the desired power output. The question on any build up is, “how much power do you want?” Unfortunately, the answer is almost always the same — as much as possible. In truth, no answer could be further from reality. You see, no one wants the power output of say a Top Fuel motor for their daily driver or even their street/strip motor. They certainly don’t want the hassles associated with keeping one alive or getting it to idle or drive in traffic.
Even at something less than this extreme example illustrates that “as much as possible” still doesn’t work as a suitable answer. If you just consider cam timing (like in our test), would you really want a cam profile designed to run at 10,000, 15,000, or even 20,000 RPM? To make as much power as possible simply requires shifting the torque curve higher and higher in the rev range. Obviously, it takes a serious motor to exceed just 8,000 RPM, let alone the numbers only possible by F1 (or motorcycle) combinations. The thing to remember here is be realistic about your power needs, especially given any budget constraints.
Now that we have extolled the virtues of making LESS power, we will show you how we made MORE on our LS3 stroker using a simple cam upgrade. Before getting to the cam swap, we needed a motor to swap them on. The LS3 stroker started out life as a simple LS3 aluminum block. The new GM block from Gandrud Chevrolet was honed to accept a K1 crank, 6.125-inch forged rods, and a set of Wiseco forged pistons. The 4.0-inch crank combined with the 4.065-inch bore to produce a finished displacement of 415c.i. In addition to the added displacement, the forged internal provided a solid foundation in case we decided to later run power adders (we always do!).
The short block was first equipped with a COMP Cams 54-470-11 cam profile. The healthy cam featured a .621/.624 lift split, a 235/251-degree duration split, and 113-degree lsa. It was combined with a set of COMP Cams hydraulic roller lifters secured using the factory lifter trays. The bottom end of the motor was completed with a Melling High-Volume oil pump, factory windage tray, and F-body swap pan.
With the short block taken care of, we turned our attention to the top end. Knowing that making power, even with the right cam profile, required plenty of airflow, we topped the 415 stroker with a set of AFR heads. The LS3 Mongoose heads featured 260cc intake ports, 96cc exhaust ports, and 69cc combustion chambers. With a peak intake flow potential of 384 cfm, the heads should allow us to maximize the power potential of our two COMP Cams. The heads were secured using ARP head studs and factory LS9 head gaskets (remember, future power adders?).
Since they work well and we had one handy, we decided to use the factory LS3 intake. The factory intake was fed by a 92mm FAST throttle body and eight 89-lb FAST injectors. To ensure the air/fuel and timing values remained consistent for the two cam profiles, we used a FAST XFI management system. Each cam was run with 30 degrees of total timing and an air/fuel ratio of 12.9:1. Naturally, we also ran long-tube headers (1 7/8-inch), a Meziere electric water pump, and a crankcase full of 5W-30 oil.
The first order of business was to run the 415 stroker with the smaller 54-470-11 cam. Equipped with the milder cam, the 415 stroker produced 607 HP at 6,200 RPM and 573 lb-ft of torque at 4,700 RPM. The combination offered an impressive torque curve, but we were hoping for just a tad more power at the top of the rev range.
Given the torque curve offered by the 415, we were even willing to sacrifice some bottom end for the extra peak power. Off came the FAST coil packs, valve covers, and rockers arms, followed by the damper, front cover and timing chain. In went our new COMP cam (.623/.596 lift split, a 247/258-degree duration split, and 113-degree lsa), followed by a quick reassembly of the stroker.
After everything was buttoned up, the motor was run in anger once again. Equipped with the new cam, the 415 LS3 produced 427 HP at 6,300 RPM and 578 lb-ft of torque at 5,200 RPM. The new cam improved the peak output by 20 HP, but gains were even greater higher in the rev range. I guess if you have a big-inch LS stroker, you need a big-inch cam!
The 415 LS3 stroker performed well with both cams, but the wilder grind did alter the shape of the power curve. Equipped with the smaller 470 cam, the 415 produced 607 HP at 6,200 RPM and 573 lb-ft of torque at 4,700 RPM. After installation of the wilder grind from COMP Cams, the power output increased to 627 HP at 6,300 RPM and 573 lb-ft of torque at 5,200 RPM. As expected, the extra power at the top of the rev range came with a slight drop in torque below 4,000 RPM.