The Buick 350 gets no love. Well, it gets very little love. Aside from an aluminum intake and ported factory iron head castings from TA Performance (TA Performance.com), there are few speed parts available for this neglected mill. That's why we were happily surprised to discover that someone developed a twin-turbo kit for the predecessor to GM's successful 3.8L V6--you know, the engine powering thousands of GM sedans and minivans on the road today. Burton Machine of East Wenatchee, Washington, builds twin-turbo kits for the Buick 350 and 455.
The $2,000 kit bolts on, except for the oil return line bung that needs to be welded to the oil pan and exhaust downpipes that must be fabricated to connect the turbos to an existing exhaust. The basic Burton kit is not intercooled, and although adding the optional intercooler is worth a fair amount of horsepower, we only tested the basic system.
It comes with two 50mm, T3/T4 hybrid turbos (T04Es to be exact) of the Chinese variety (to keep the cost down), a pair of sheetmetal exhaust manifolds, two 35mm wastegates, a carb hat, and the piping to connect it all. The wastegates come with either 6- or 8-psi springs to control the boost level. What the kit does not come with is all the little stuff you need to make it work: T3-style exhaust plates, a high-output fuel pump and boost-referenced fuel pressure regulator, exhaust manifold mounting bolts, and all the plumbing to oil the turbos. You may also need a carb modified for blow-through boost application. In the end, we spent an additional $1,200 for a grand total of $3,200 to make the system functional. Was it worth it? Absolutely.
A junkyard-fresh Buick 350 stuffed into a 20-foot long '63 Buick LeSabre wagon served as our test mule. The Burton kit is designed to fit '68 to '72 GM A-body cars, but it also fits the X-frame wagon chassis and even clears the stock hood. Our engine came from a one-owner '72 Buick LeSabre four-door that was used as a daily driver for a traveling salesman. The owner was meticulous about changing the oil every 3,000 miles, but it still showed the wear and tear of a lifetime on the road. According to the owner's son, it was never opened up. Buick rated it at 174 hp at the crank, which is weak. It was in dire need of more ponies. We bolted on the turbo system without changing anything on the stock engine; we even left the stock cast-iron intake manifold in place.
For the fuel system, we got a Quick Fuel 650-cfm carb with annular boosters (PN SS-650-BAN) designed for blow-through applications. Quick Fuel also provided an 18-psi fuel pump and boost-referencing pressure regulator. For every psi of boost, you need an additional 1 psi of fuel pressure. The Quick Fuel carb is a standard square-bore, whereas the intake was designed for a spread-bore carburetor, so we had to add an adapter. Even with the adapter, there was a clearance issue with the Earl's dual-feed fuel line and a factory boss on the intake, which we ended up cutting off. Although there is a ton of room behind the engine, the new exhaust downtube limited the car to either a single-reservoir master cylinder and power booster or a manual dual-reservoir. Since this wagon had front disc brakes, we opted for the latter.
We also added an MSD Pro-Billet distributor and 6AL-2 programmable ignition box. The 6AL-2 has a boost-referencing retard feature to pull timing based on the boost level. This is important because boosted engines require less timing advance than naturally aspirated engines. Reducing the amount of spark advance moves the moment of peak cylinder pressure further away from the moment when the piston reaches top-dead center. If the ignition fires too early and peak cylinder pressure builds before the piston begins to travel back down the bore, the pressure wave can hammer the bearings, break the piston, pinch ring lands, and so on. At our boost level, the likelihood of major damage occurring is small, but should we ever turn up the boost, we'll definitely need to take additional timing advance away from the engine. The MSD software makes that job easy and precise, and we can program a boost timing curve based upon manifold pressure and engine rpm.
Our engine is bone stock, with ring gaps that aren't suited to the high pressure and heat that come with lots of boost, so we started with a mild 6 psi. This would allow us to run pump gas and avoid knocking holes in pistons or sticking a ring in the bore. We set the base timing at 8 degrees with 26 degrees of total timing. We then programmed the 6AL-2 to remove 1 degree of advance for every 1 psi of boost for a very conservative total of 20 degrees of advance at WOT. The engine responded well to the added boost with no signs of detonation, giving us the confidence that it would live on 8 psi. Even 10 psi might be possible with these turbos and the stock internals in a fresh engine with substantial ring gaps. We made eight dyno runs, and after carb-tuning, the Buick made 276 hp and a whopping 365 lb-ft at the rear wheels. If we assume a 20 percent loss from the TCI 200-4R trans, and 91?4 axle with 3.08:1 gears, that is 350 hp and 460 lb-ft at the crank, which is double the original output of the engine--unusual for just 6 psi, so perhaps the drivetrain losses are lower than our estimate. What is impressive is where this engine makes that power--the torque peaked at 3,400 rpm, while the horsepower peaked at just 4,750 rpm. This is a low-revving torque monster.
The stock cam and valvesprings are a hindrance. The boost is all in by 2,000 rpm, and the power drops off at 5,000 rpm. At 5,500 rpm, the valves start to flutter. A spring upgrade is certainly worth the price of admission, and if we ever rebuilt the engine, we'd certainly look at upgrading the cam to something with more exhaust duration and a different LSA. As a point of reference, the owner of this wagon also built a '71 Buick 350 for a GS convertible. The head work alone cost $2,500, and the end result was 400 hp and 414 lb-ft for a little more than $7,000. For less than half that price, this worn-out stocker came within 50 hp, and although it won't last as long, there is room to add more power if we added a better bottom end and valvetrain. You gotta love turbos.
