Welcome back to our project LT motor build. As you'll recall in the April 2013 issue of GM High-Tech, we tested a bunch of simple mods for the admired LT motor and came up with some token gains that came in small increments. We have decided to throw some bigger and badder parts at this thing to show the levels in which this motor can still perform. We saddled up and went back to TPIS in Chaska, Minnesota to see what they had come up with. We chose some popular choices you guys out there will most likely be looking at when choosing to upgrade the power in your LT1. The theme for these modifications is more air equals more power!
Test #1 – Our baseline motor
Max Power – 340.3HP, 374.5TQ
Avg Power – 279.7HP, 348.1TQ
First, let's recap. We started with a basic stock GM LT1 engine with a .040 bore with a stock crankshaft, heads, exhaust manifolds, intake, 1.5 rockers, oil pan, OptiSpark, 48mm throttle body, 24-pound injectors and the stock fuel pressure set at 43 psi. We upgraded a few parts to make sure it didn't grenade on us accidently. The parts we upgraded were the factory rods to Scat versions with a stock length, Speedpro hypereutectic flat top pistons and a zero decked block with 10.5:1 compression. Fuel was the typical blend you'll find at any gas station with a 91-octane rating.
During our first round of tests we upgraded the plugs and wires, added a 6AL MSD box, a TPIS airfoil, an Airaid air filter, a larger MAF housing and an electric water pump. This all added up to a respectable 336 horsepower and 380 ft-lb of torque. As with all things, we ran into a problem with the electric water pump and had to replace it with a stock unit. Thankfully the water pump isn't driven by the crankshaft so we didn't get too excited about its loss.
We reran the motor to make sure our numbers were consistent with where we left off. Our baseline numbers reassured us that we were pretty close to the previous tests and had a solid number. Again, as with the last set of tests, we ran each part through three dyno runs to make sure none of them got a bum pull. And just like the previous tests, each of these will be progressive, meaning that unless otherwise specified all parts will be left on the engine for each subsequent test.
1. Jim at TPIS gets the motor ready for the first cam swap. This is quite an involved proc
2. A set of Comp Cams Pro-Magnum rockers was added to see if we could squeeze a few extra
3. It’s pretty easy to tell that the stock throttle body is just a giant choke point in th
Test #2 – A popular header bolt-on
Max Power – 353.8HP, 389.6TQ
Avg Power – 289.0HP, 358.5TQ
Cost – $700 (uncoated)
As we mentioned last time, an engine is essentially a glorified air pump with the basic theory that more in and more air out means more power. We surmised after the last tests that this engine was being highly restricted by the stock exhaust and could benefit from a set of headers. A set of headers allows the exhaust gases to exit the engine more efficiently by having a larger tube for the air flow. This allows the air to exit the heads faster which means more power. The primaries on the stock units are quite small and restrictive. These TPIS long tube headers made for the 93-97 Camaro and Firebird, boast 1.75-inch primaries with a 3-inch collector and are made of mild steel. We were relatively pleased with the results, we made a solid 10 horsepower throughout the power band and 15 peak ft-lb of torque. Headers are a must with any performance build and this test just proves that even a mild build can really benefit from a set of headers.
Test #3 – A bolt on 52mm throttle body
Max Power – 357.9HP, 401.1TQ
Avg Power – 295.7HP, 366.9TQ
Cost – $280 with exchange
The stock 48mm throttle body is quite small, let's be honest. That means a lot less air is getting into the combustion chamber and robbing you of power. Any constraint in the air flow into the intake is going to steal power from you and this is no exception. A larger throttle body will obviously allow more air flow and hopefully more power. For this test we used the TPIS 52mm throttle body and for the cost it seemed like a decent buy. We gained roughly 6 horsepower and 8 ft-lb of torque through the powerband on average. Not a bad performance, but we think that we'll see a greater effect from this piece with more impressive parts.