Performance Tips for a 1979 Buick 3.8 V6by Richard Rowe
The Buick 231 (3.8-liter) V-6 is one of those unsung heroes of the automotive world, with a provenance stretching back nearly as far as the Chevrolet small-block. The Buick 90-degree V-6 was based on the all-aluminum 215-cubic-inch Fireball V-8, developed during the mid-1950s and introduced in 1961. Buick subsequently sold the design to Rover, bought it back, hacked off two cylinders and added a turbo. This motor would continue in production largely unchanged until it evolved to become the GM 3800 Series One in 1988.
Replace and Port the Heads
Your 231's stock heads will flow about 120 cfm (cubic feet per minute) of air at 0.500-inch lift, which will only support about 210 horsepower at a maximum. Buick built a number of factory-upgraded Stage I and Stage II parts for later turbo cars, but these heads and intakes are tremendously expensive and hard to find. A set of stock 1984-1987 Grand National Turbo heads will flow about 180 cfm to support 275 horsepower.
Re-work the Heads
All Buick 3.8-liter heads have the same basic inherent shortcomings, and are the biggest restriction to airflow in the engine. Gasket-match the intake and exhaust ports, and reshape the bowl area (the pocket below the valve head) to smooth them into the valve seats. Rework the short-side turn radius (the bottom of the port where it bends down toward the valve) on both the intake and exhaust to straighten and smooth it out. Fill the exhaust crossover, cut a 3-angle valve job into the valve seats and smooth out the combustion chamber to remove casting ridges. Replace the stock 1.71-inch intake and 1.5-inch exhaust valves with 1.775-inch intake and 1.6-inch exhaust valves, and replace the stock valve springs with Chevrolet LT1 valve springs. Ported turbo heads that flow between 205 and 220 cfm will support about 320 to 330 naturally-aspirated (non-turbo) horsepower.
Replace the Pistons
The stock Buick pistons are a lot bigger and heavier than they need to be, and the engine can withstand far more than its 8-to-1 compression ratio. Replace the pistons with a set of thinner, lightweight, 2618 forged aluminum pistons designed to yield a 10-to-1 compression with 29 cc cylinder heads. Coat the piston tops, combustion chamber roofs and the insides of the intake/exhaust ports with thermally-insulating ceramic powder-coating. This will increase octane tolerance and will keep combustion energy in the chamber and exhaust to make power instead leaking out to heat the water in your cooling system.
Induction and Exhaust
Install a single-plane aluminum intake or a high-performance dual-plane intake, a 390 to 400 cfm carburetor (dump the fuel injection unless you're planning to use a turbo) and a set of race headers with 1.5-inch primary tubes. A camshaft with about 15 to 18 degrees more duration at 0.050-inch lift and about 0.450-inch intake lift and 0.500-inch lift on the exhaust will work best with you ported heads; flow gains over 0.500-inch are fairly minimal, and with any more duration your engine will idle like an asthmatic jackhammer.
Richard Rowe has been writing professionally since 2007, specializing in automotive topics. He has worked as a tractor-trailer driver and mechanic, a rigger at a fire engine factory and as a race-car driver and builder. Rowe studied engineering, philosophy and American literature at Central Florida Community College.