Performance Tips for an LT1 Chevroletby Richard Rowe
Nothing is so inevitable as change -- that was reality that Chevy fans everywhere had to face when GM began phasing out the old small-block for the updated LT-Series engine. While minor revolutions brewed in the ranks at first, it didn't take long for enthusiasts to embrace the LT and its notable performance updates. The LT1 was just cleaner, more modern and more efficient. Right from the factory, the LT and its new heads proceded to set the standard for V-8 performance in the new millennium. The LT1 continues to be an immensely popular engine among hot-rodders, particularly since they're at least as cheap and easy to find as any old small-block.
Stage One -- 20 to 30 Extra Horsepower
General Motors made no secret of the fact that it left a good bit of power on the table in factory LT1 cars. Granted, it was a bit harder to find than on older engines, saddled as they were with compromise emissions parts and induction systems. But the potential for power is there without ever cracking the valve covers. On your average LT1, a new set of performance plug wires and plugs will net about 5 horsepower at the wheels, and a cold-air intake should be worth 3 to 5 horsepower. LT1 builders have kind of a standard bolt-on package that's worth a steady 20 horses and 25 foot-pounds on your average F-Body Camaro: A good cold-air intake, cat-back exhaust, electric water pump and underdrive pulleys should take a solid half-second or more off of your quarter-mile time. A computer tune should net you a further 5 to 10 horsepower after these basic mods.
Stage Two -- 320 Horsepower
If you want a bit more go-power, you'll need to start dealing with your engine's breathing apparatus. Along with your cold-air intake, install a larger MAF sensor housing like those offered by Granatelli. Next up comes a big 58 mm throttle body, which won't fit on the stock intake without enlarging the intake's throttle body bores to match. This is something you can do yourself if you've got a die grinder; simply remove the upper intake, scribe a pair of 58 mm circles on the intake using the aftermarket TB gasket, and start carefully grinding away the excess material to match the TB bores. If you really want to gain some power, you can send your stock manifold out to be extrude honed to enlarge the passages -- or you can skip all of this and buy an aftermarket manifold. Combine these intake enhancements with a set of ceramic headers, 1.6-to-1 roller rockers, and the basic bolt-ons, and you should see at least 310 to 330 horsepower.
Stage Three -- 400 Horsepower
Some will tell you that if you're serious about performance, you have to start with either LT4 or aftermarket heads -- and that might be true if you have unlimited money and horsepower goals. But the reality is that, while LT4 heads do have larger valves and better port designs, there's plenty of potential in the stock LT1 heads after a bit of porting. More to the point, LT4 heads require LT4 manifolds, and aftermarket heads are wasted without a new manifold. You can save quite a bit in terms of parts buy-in and ancillary costs by porting your own heads; a gasket-matching job, basic bowl blending, blending the area behind the valve support and smoothing out the short-side turn on the bottom of the port can give you 400 horsepower potential when used with the previous bolt-ons and a somewhat more aggressive cam with 232 intake and 240 exhaust degrees of duration at 0.050-inch lift, and 0.578 and 0.574 inches of lift.
Stage Four -- 500 Horsepower
It's possible to make 500 horses on the stock cast crankshaft, but you're really pushing your luck after 450 horses -- especially if you use a power adder like nitrous to get there. At this point, forged crankshafts and rods are so cheap that there's almost no debate over whether or not to keep the stock rotating assembly for serious builds. The same can be said about building stroker engines, since a forged 383 stroker rotating assembly costs no more -- and perhaps even less -- than buying forged components of stock specification. That's why you see so many 383 stroker LT engines out there. Increasing displacement, in itself, might not increase horsepower with the ported stock heads, but it will make your engine more street friendly by making more low rpm torque and lowering the powerband. If you want to make more than 420 to 450 horsepower without nitrous or supercharging, you'll need to upgrade the heads with aftermarket or fully ported LT4 units.
Stage Five -- Really Big Power
The LT engine is more than capable of holding 800-plus horsepower -- it just needs a bit of help to do it. If you've already done everything in Stages One through Four, including forged pistons to go with the rest of your forged assembly and a 383 stroker crank, then you can easily spray your way to 750 horsepower with a direct-port nitrous system. Just make sure to reinforce the engine with a full set of chrome-moly studs and fasteners below and on top. Any number of centrifugal superchargers will make 600 to 800 horsepower on this engine with the above-mentioned modifications, but you may want to seriously consider going with a pair of turbos. Turbos don't suck power from the engine like superchargers do, meaning that you can make the same power with lower boost than you would need with a supercharger. For this reason, turbos have greater power potential, get better fuel economy and run on lower-octane gas for any given power level compared to a supercharger. That's especially relevant if you're running higher than 8.5-to-1 compression, since higher-compression engines are less tolerant of high boost than lower-compression ones.