Armed with this knowledge, if you're considering an LT1 swap, the general consensus among LT1 Internet geeks is that engines from the B/D-bodies make the best swap candidates, since they were in thousands of cars that are making their way to the junkyard at this very moment. They have a couple of other things going for them. They all have the upgraded Opti-Spark unit, and because their overflow reservoir is mounted higher than the engine, their system of coolant lines and vapor vent tubes is the least complicated. Also, unlike most F-body applications, they were all dual-catalyst cars-a huge plus to guys living in states with tight emission laws. By those states' guidelines, if the engine was originally a dual-catalyst application, you are able to run a true dual exhaust in your project car. If not, you're stuck running a Y-pipe into a single cat.
If you are scoping out a Caprice in the junkyard, beware the 4.3L V-8. Though it looks the same as an LT1, it is a low-compression, grandma-friendly engine that would make for an embarrassing swap into a performance car. Let the VIN be your guide-a P in the eighth position of the vehicle identification number is what you should be looking for. A W indicates the engine in question is the 4.3 that will turn your hair blue and make you walk with a cane. RPO geeks can also check the sticker on the inside of the trunklid. The regular production option code for the 4.3 motor is L99. If all else fails, check the exhaust. All LT1 cars ran true dual exhaust, while the 4.3 cars were all single catalyst, single tailpipe.
There is one fitment issue that seems to crop up in all LT1 swaps we've seen so far. The A/C compressor won't clear the passenger-side framerail of most musclecars. An idler pulley is available for those who have no use for air conditioning, but some ambitious swappers end up notching the frame for clearance. Because of the front-mount water pump and distributor, GM stacked all the engine-driven accessories up on one side of the engine. The B-, D-, and F- bodies mount the accessories on the passenger side, while they're on the driver side in Corvettes. The Y-body accessory-drive system is usually expensive, but if you can find one it may solve most of the clearance issues.
Regardless of which car you pull an engine out of, be sure to grab all its accessories, brackets, coolant lines, and wiring. You can rewire the factory harness to fit your car or buy a premade harness from Painless Performance Wiring or Street & Performance. The harnesses use OE-style wire colors and connectors and can be made to fit your application and plug into the factory ECM, which can be fully reprogrammed by tuners like PCMforless.
Be Heard
Still interested in reading more about LT1s after all this? We think LT1s are worth another look and are considering a buildup and possible swap into an older car. But we want to hear from you. Whether you want to see an LT1 buildup or feel like canceling your subscription when you see another small-block Chevy, we want to hear from you. Send us your feedback at CarCraft@sourceinterlink.com or in the CC forums at CarCraft.com.