Late Buick Odd Fire V6 HEI Distributor - Short Shaft

The TSP HEI Distributor for the Buick 90° odd-fire V6 is a direct-fit ignition upgrade for carbureted 225 CID (3.7L) and 231 CID (3.8L) odd-fire V6 engines produced from 1975 through 1977. The self-contained large-cap HEI design integrates the ignition coil, ignition module, cap, and rotor into a single unit, connecting to one 12-volt source with no external coil, ignition box, or condenser required.

The 65,000-volt internal HEI coil delivers significantly stronger spark output than a factory points-style distributor, supporting easier cold starts, cleaner idle quality, and more consistent ignition performance across the RPM range. A magnetic pickup trigger replaces the mechanical points contact and requires no routine maintenance. Both mechanical and vacuum advance are included, with a vacuum advance adjustment tool shipped with the distributor for advance curve tuning.

The Buick 90° odd-fire V6 was used across multiple GM divisions in 1975 through 1977, appearing in Buick, Oldsmobile, and Pontiac vehicles before GM transitioned to the even-fire crankshaft design beginning in the 1977 model year. This distributor fits the odd-fire engine architecture specifically. It is also compatible with the earlier Dauntless 225 CID V6 with a slight intake manifold modification for clearance.

Understanding the Buick Odd-Fire V6 and Why the Distributor Matters
The Buick 90° V6 produced from 1975 through early 1977 is known as an "odd-fire" engine because its 90° crankshaft creates uneven firing intervals — cylinders fire at 90° and 150° alternating intervals rather than the even 120° spacing of a true even-fire design. This architecture requires a distributor specifically calibrated for the odd-fire firing order and timing characteristics. Installing an even-fire distributor on an odd-fire engine — or vice versa — will result in misfires, poor performance, and potential engine damage. Verifying that your engine is odd-fire before ordering is critical, especially for 1977 model year vehicles where both designs were produced.

Performance Benefit
Replacing a worn or points-style distributor on a Buick odd-fire V6 with an HEI unit delivers immediate improvements in starting reliability, idle quality, and part-throttle drivability. The 65,000-volt internal HEI coil fires spark plugs more consistently than a factory points setup across the full RPM range. The magnetic pickup trigger holds timing accurately without the wear and drift inherent in mechanical points contact. Both mechanical and vacuum advance are included, and the vacuum advance adjustment tool allows the vacuum curve to be tuned to your engine combination and driving conditions.