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Make a Plan
The Chevy 350 engine works extremely well in the S10 and GMC S15 chassis; if nothing else, even a bone-stock 350 is a sure 25 boost in horsepower and torque over the already fairly stout 4.3-liter V-6 engine. For many, this -- combined with a V-8 exhaust note and tire-shredding capability at will -- will be enough. But a 350 S10 can be anything from a simple, tire-shredding beater to a half-million-dollar, nine-second monster with air conditioning, antilock brakes and all the latest suspension tech. Before diving in, you need to realistically assess your budget and your expectations. If you've already got a truck and a donor vehicle, and you're doing all the work yourself, this swap is doable for $1,000 or less. If you don't have a donor vehicle and drivetrain, you could spend anywhere from $3,000 to $8,000, depending on what you're after. Remember the old adage about time, talent and money: the less you have of one, the more you'll need of the other two.
Get a Complete Donor
You might be tempted to go to the junkyard and grab the first 350 and TH350 transmission you trip over, but don't do it. The money you'll save buying everything you'll need piecemeal will come back to nickle-and-dime you to death later on. A bracket here, a transmission linkage E-clip there, a longer throttle cable or an alternator bracket -- these things add up. Complete 350-powered trucks are very cheap, and offer an entire drivetrain in a box. This is especially critical if you're looking for a more modern engine with fuel injection, a computer-controlled 700-R4 or 4L60-E or anything other kind of electronic component. In this case, a donor vehicle is a complete necessity, unless you're all right with spending a lot of money to build a full aftermarket electronic control system. It doesn't end there, either, because the donor vehicle can provide you with some chassis parts you might find useful; more on that in a moment. TBI engines with 700-R4, 4L60 or T-5 transmissions work best for this swap. You may need to get a high-mount alternator bracket to clear the steering components.
Get a Kit and Get it in
Physically getting a 350 engine into an S10 chassis may be the simplest part of the entire swap. If you've got a 4.3-liter truck, a 350 and TH350 will almost bolt right in; you may have to modify or replace the transmission crossmember, but otherwise, it's almost a straight swap. There's even a good chance that the driveshaft yoke will slide into your new TH350, TH400, 700-R4 or 4L60 transmission. But, if it doesn't, have the donor vehicle's driveshaft shortened and fitted with the old driveshaft's differential flange. But if you're not one of the lucky ones for whom this swap is a near bolt-in, you can buy complete swap kits for $600 to $800 that include swap engine mounts, a set of headers, a 7-quart, rear-sump
oilpan to clear the crossmember, all the hardware and gaskets you'll need to get the engine in your truck, and very comprehensive instructions. When purchasing a kit, get one that relocates the engine back a few inches; the 350 is longer than a V-6 and, while it will physically fit behind the radiator, you'll have almost no room between them. You may need to modify the firewall a bit to clear the engine, but it's usually nothing a large hammer can't handle.
Making it Work
Anyone who's ever bolted anything together can get a 350 engine sitting in an S-10 just by following the directions included with the swap kit. But the devil is in the details insofar as making everything work together so you don't wind up with a foul-tempered, over-heating beater that you can't trust to get to work. The stock S10 radiator is nowhere near strong enough to cool a 350; the aftermarket offers radiators specifically made for this swap, but C3 Corvette radiators are popular retrofits that work well. You may need to move or modify the core support to install it. The stock S10 axle and differential might survive for a little while if the truck was originally a V-6, but it will grenade when combined with a decent set of drag tires and more than 300 foot-pounds of small-block torque. Ford 9-inch axles narrowed to fit are popular, but you may be able to save some money narrowing your donor vehicle's axle. Hypothetically, you could just use the donor axle with fender flares and wheels with massive offset -- but it looks weird, and all your friends will know you cheaped out on the axle.
Like the T-Bucket, the sky is the limit with this configuration, and you can optimize it for almost anything. But the one thing you'll want to do no matter what is to install stiffer front springs to handle the 350's extra mass, especially if you started out with a smaller V-6 engine or an inline-four. Stiffer front springs are a must for handling, and weak front springs won't help your now traction-deficient truck hook any better. Speaking of which: ditch the stock rear suspension, and go with a full aftermarket four-link system utilizing adjustable, tubular links. You'll probably want to install larger rear tires and mini-tub the bed to fit them, and not only will the stock suspension get in your way, it doesn't have the wherewithal to deal with the twist you'll be putting through it. Yes you can use it, and many people do -- just as many people have trucks that do unintended 360s at intersections in the rain, while overheating. If you want a 350 S10 you can be happy with, treat the entire truck as a system, upgrading your chassis, brakes and drivetrain to make it all work together. Or, you can ignore all that and wind up with the ill-tempered, evil-handling, homicidal little monster mentioned earlier. It's your hot-rod, and your call.