RHS LS1 Engine Build - Trial By Fire

We opted for a set of LS7 rocker arms, which have been upgraded with CHE bearings. These are a much better bearing than the stock needle bearings and a must for anyone turning high rpm on a consistent basis. The stock LS7 valves are wrapped in Comp Cams 926 valvesprings, which are good up to 0.675-inch of lift.

As with any tall deck, installing a normal intake manifold requires using a set of spacers. Since FAST and RHS work hand in hand, these were easy to make and equally as easy to come by.

The crowning jewel of our RHS 502, the FAST LSXR 102 with a matching Big Mouth 102mm throttle body. If you ever wondered how much the LSXR could flow, this is the real test.

Remember those -12 AN fittings on the side of the block for a dry sump? We did, and decided they would definitely benefit us in this application. Even though the new block has improved windage and bay-to-bay breathing, the dry sump provides even more oil control.

Just look at this thing, it's gorgeous! To the untrained eye it may look like a standard LS1 and that's just the way we like it. With 502 cubic inches hidden in such a small package, you just can't go wrong.

The Comp Cams SuperFlow SF-902 is certainly not known for its generosity, but we were after consistent, solid numbers. Rich is tuning our combo with a FAST XFI system, which allows finite control over every tuning parameter. With eight separate EGT and wideband 02 sensors, Rich can dial in and measure everything perfectly.

How does 657 lb-ft of torque at 4,600 rpm sound? How about the 625 lb-ft at 3,700 rpm, or the 575 at 6,000! This 502 is just a torque monster and definitely not at the cost of horsepower. 651 horsepower at 6,000 rpm is respectable, especially with stock LS7 heads and small, 1.75-inch headers. But, of course, we had to make more.

So, while we waited for a new Comp Cam camshaft to be ground, we removed the FAST LSXR 102 and installed a stock LS7 intake in its place. We immediately lost 8-10 horsepower and a similar amount of torque across the entire rpm band, proving that this is a well-designed piece.

With the LSXR back on and power restored, we made another run and logged manifold pressure. With 502 cubic inches consuming as much air as possible, we found almost no restriction in the intake, seeing a flat 100kPa across the board. It was clear that the stock LS7 heads were the limiting factor, not the intake. At which time, RHS/Comp suggested a solution to this problem is in the works.

The masters at Comp Cams ground us a new camshaft, hoping to give up some low-end torque for a lot of upper-rpm horsepower. The new cam came with 255/265 degrees of duration, 0.675/0.675 inches of lift, and a much tighter 115 lobe separation angle.

And what a difference it made. Horsepower was way up to 676, but instead of stopping at 6,000, we were able to spin all the way to 6,600, with a much loftier curve. We did give up 25 to 30 lb-ft of torque down low, but we highly doubt anyone would mind. Of course, with how versatile this block is, you can make any type of power you desire.