LS1 Engine Performance Build and Dyno Test Written by Jim Smart on September 18, 2017 It can be safely said GM’s all-new LS1 opened the door to a new world of technology and performance in the 1990s. It can also be accurately stated the LS family is easily the most successful V-8 in American automotive history aside from the time-proven small-block Chevy, which remains in production 63 years later. We consider the LS engine something of a lesson in perfection—cathedral style intake ports, evenly spaced elliptical exhaust ports, fulcrum pivot rocker arms, a skirted cross-bolted block with a tall deck, steel crank, and a host of other great features. GM took all of the best attributes of the small-block Chevy and small-block Ford and rolled it all into the skirted LS. The LS has only gotten better with time and more advanced engineering, leading up to the LSX. To return to the original LS pushrod V-8 has been a privilege because this has enabled us to examine how far Chevrolet has come with this engine. If you’ve got a vehicle powered by the LSX you know what we mean. It is great fun working with such an incredible engine. Last time, we took you through the machining and build up of a 5.7L LS1 being built by L&R Engines just south of Los Angeles in Santa Fe Springs. These guys pay extreme attention to detail in all of their engine builds. You never know what you’re going to see at L&R Engines. Their work ranges from commonplace small-block Chevys and LS mills to Studebakers, Packards, classic Chrysler Slant Sixes, Detroit diesels, and more. If it sucks, squeezes, bangs, and blows L&R knows what to do with it. We have machined, cleaned, and assembled our LS1. Now for the home stretch of this project that includes a valve job and final completion, and a date with a Dynojet 902 at Westech Performance near Riverside, California. The beauty of the LS is its wonderful simplicity—two gorgeous aluminum castings stacked on top of a groovy skirted Y-block ready for just about anything you can throw at it. We wanted to dyno test this LS1 two ways: one with the FAST LSXR 102mm intake manifold designed for car applications like the Camaro, Chevelle, Nova, and Corvette and one with the tall Dorman or FAST LSXRT intake designed for truck and SUV applications. The difference in the two intake manifolds is clear. The FAST LSXR 102 manifold employs short runners designed for high-rpm horsepower and torque. The Dorman truck/SUV intake manifold turns its attentions mostly to low- to mid-range torque with less focus on horsepower. We were unable to test the Dorman or the FAST LSXRT intake because we weren’t able to source the appropriate fuel rails in time to meet deadline. However, we can tell you the Dorman OEM replacement intake with its long intake runners is engineered for raw twist in a truck. Ditto for the FAST LSXRT truck/SUV intake for LS vehicles with a higher hoodline. Let’s wrap this thing up. 1. We’re working with the original LS1 cylinder head castings sporting 2.000-inch intake and 1.550-inch exhaust valves. We have replaced the valves and guides with Speed Pro parts and cut fresh seats. Chamber size is 66.67cc. We’re confident that with some good custom port and bowl work along with a hotter cam we would have pushed this thing closer to 500 horsepower. 2. You’ve got to love the LS1’s cathedral intake ports, which were a quantum leap size-wise when they arrived in the late 1990s. It doesn’t take much to get power from these ports. 3. LS1 exhaust ports sport a straightforward angle with a high ceiling, which means excellent scavenging. Perform a little port work and these guys will flow. We had to chase the spark plug holes, which had minor thread damage. 4. When we began this LS1 build we threw all of the stock bolts in the recycle bin. If you want it bulletproof, you’ll have to opt for ARP fasteners throughout. We chased threads in the bolt holes and were sure to use a thread lubricant. 5. LS engines sport lifter guides/holders, which drop right into place as shown. These hydraulic rollers from Comp have been lubricated with assembly lube. 6. Fel-Pro head gaskets have been laid down on hospital-clean surfaces. We’re ready for the cylinder heads. It is virtually impossible to screw this up. Fel-Pro marks the head gaskets “FRONT” for easy lay-down. 7. The cylinder heads were installed and torqued to specifications in proper order. Keep in mind that factory cylinder head bolts can’t be reused because they are torque-to-yield bolts. ARP bolts are not torque-to-yield and are torqued like conventional cylinder head bolts. 8. The valvetrain is installed and torqued to proper specifications. Make sure the rocker tip is centered on the valve stem. 9. Shown here is the stock harmonic damper, which is not what we installed in Part 1. We showed you the Summit Racing underdrive harmonic damper, which reduces accessory speed and frees up power. Harmonic damper selection depends on how you intend to use your LS1. 10. We opted for a stock LS water pump, which we ordered from Rock Auto. No real preparation is necessary, just make sure the contact surfaces and the seals are clean before you bolt it on. 11. The valve covers are installed next, incorporating Fel-Pro seals. 12. FAST engineers teamed up with airflow specialists at RHS to develop polymer intake manifolds for GM LS engines. While the LSXR features a 102mm air inlet that is perfectly suited to the FAST Big Mouth 102mm throttle body, we’ve opted for the 92mm throttle body. Other features include integrated nitrous bungs and perfect bolt-on fitment that allows the use of factory accessories without modification or clearance concerns. We’re running 36 lb/hr FAST injectors, which will work fine with our 5.7L and a hot cam. 13. Especially cool is this 92mm throttle body, ideal for street and strip, that arrives on your doorstep in a convenient protective carrying case (seriously!) packed in foam. FAST throttle bodies include an idle air control (IAC) solenoid and a throttle position sensor (TPS). 14. Our completed LS1 at L&R Engines is ready to go on the dyno. 15. Steve Brule of Westech Performance gets our LS1 ready for a series of pulls using the FAST system. Engine oil is added for the break-in. 16. Our FAST LSXR 102mm intake manifold is installed and set up with 36 lb/hr injectors and FAST fuel rails. 17. This handsome induction package netted us 447.8 horsepower and 434.6 lb-ft of torque.