Hot rodders have known about the power of the Gen III/IV for quite some time, and it’s not news to anyone that they’re being dropped into just about everything. They’re so popular, in fact, that many engine shops now report that conventional builds are on the decline. That sounds downright wacky at first, but think about it for a short while and it makes perfect sense. Not only can you make 650-plus streetable horsepower with an LS small-block these days, but you can build them as large as 500 ci. Throw in the weight and handling benefits of an all-aluminum platform, especially in Pro Touring projects, and the swap appeal of these motors becomes quite obvious.
Whether plans call for a 9,000-rpm screamer or a stock salvage yard score, swapping an LS motor into classic Bow Tie muscle is easier than ever. Several aftermarket manufacturers offer engine mounts, headers, oil pans, and transmission crossmembers that make an LS retrofit a strictly bolt-on affair. Even so, there are lots of potential hiccups that can easily be avoided with a bit of research. Gen III/IV small-blocks rolled off the assembly line with a number of different front accessory drive, intake manifold, oil pan, and throttle-body designs, all of which can affect how smoothly your swap progresses. To get to the bottom of it all, we had a chat with Marc Lewis of Hedman Hedders, Liz Miles of Hooker Headers, and Mark Campbell of Street and Performance. Here’s their advice for a fruitful LS swap.
Marc Lewis: Swapping an LS motor into a muscle car used to require very expensive custom headers, but that’s not the case anymore. The application list of Muscle Rods LS swap products manufactured by Hedman Husler Hedders is a virtual alphabet soup of iconic GM cars and trucks. Unlike some products that can be produced as a one-size-fits-all product, headers cannot. Header primary tubes are built using rigid, immovable tubes. When a manufacturer designs a set of headers, they must determine the most effective path to use for the tube routing, so they do not interfere with steering or suspension components, auxiliary engine/vehicle components, crossmembers, or chassis components. Change any of the variables in the engine compartment, and you risk hitting any number of items. This can bring your installation to a screeching halt. Although many installers like to use the gentle persuasion of a hammer to make a set of headers fit, this is not what most manufacturers intended for you to do. Not only will banging on your tubes negatively affect the performance you expect to gain from the headers, a beaten set of headers just doesn’t look very good under the hood.
For the reasons mentioned above, Hedman Husler has invested countless hours developing its LS swap headers and motor mounts to ensure that they fit right in without any need for massaging. The R&D team at Husler’s Georgia plant did this by bringing in specimen vehicles that matched the most frequently used setups. While on the racks, the Husler designers develop mid-length and long-tube headers in a variety of diameters, as well as companion motor mounts and transmission crossmembers. The Hedman Husler guys basically did all the trial-and-error work before the parts ever hit the market. These headers are currently in production for Chevy Tri-Five and X-frame cars, as well as A-, B-, F-, G- and X-bodies. We also offer a range of headers for ’67-98 two-wheel-drive GM half-ton trucks and SUVs.