Like General Motors' Cadillac and Oldsmobile divisions, after World War II Pontiac began development of an overhead valve V-8. However, the conservative leadership of the company elected to stick with the Flathead inline-eight that had been around since 1933. A change of philosophy came with new leadership; Robert Critchfield became general manager of Pontiac in 1952 and under his guidance, development of a new engine began again.
Introduced in 1955, Pontiac's Strato Streak OHV V-8 had a displacement of 287 ci and was slightly bigger and heavier than the 265 Chevy introduced the same year. Although it may come as a surprise to Stovebolt fans, a Pontiac engineer by the name of Clayton Leach developed the stamped-steel, stud-mounted rocker arm system, reportedly while working in his home's basement. Interestingly, Ed Cole, Chevy's leader, asked for, and was given, permission to use Pontiac's engineering.
Over the years Pontiac produced a huge array of engines, with displacements of 265, 287, 301, 317, 326, 347, 350, 370, 389, 400, 421, 428, and 455. And while the division had a reputation for building engines that were powerful and reliable, government emissions standards and massive testing costs for individual powerplant combinations dictated that General Motors embrace a corporate-wide engine philosophy—so Pontiac's last V-8 was produced in 1981.
Before engine production ceased Pontiac had established a remarkable reputation for performance due to engines like the two four-barrel-equipped 317 introduced in 1956; the 347 in 1957 with three-two barrels that was available in NASCAR-certified 290 and 317hp trim and the Bonneville models with Rochester fuel injection similar to the system used by Chevrolet (Pontiac didn't publish horsepower numbers for this engine, probably because it made less horsepower than the carbureted version and was more expensive). Displacement was bumped to 370 ci in 1958, a single four engine making 315 hp along with two Tri-power–equipped versions—300 hp and the NASCAR certified 315 were offered. Fuel-injection engines were still available and were rated at 310 hp.
There were many other noteworthy Pontiac powerplants that continued the performance theme, such as the Ram Airs, H.O.s, and Super Duties. But while all these Pontiac engines were formidable, the workhorse of the group was the 389 introduced in 1959. Produced in a host of configurations, arguably the best of the bunch was found in GTOs produced in 1965 and 1966. Cranking out enough torque to propel a 3,600-pound car to quarter-mile e.t.'s in the 14-second range, they were docile, reliable, and easy to live with—all things considered they have everything it takes to be a great vintage engine for a street rod.
Our fellow gearhead, Paul Willis, is a former GTO owner, has a blown Pontiac-powered 1932 sedan, and when the opportunity came to buy a 1932 Ford pickup powered by a 389 he couldn't pass it up. Unfortunately the engine could be charitably described as tired, so he turned to John Beck at Vintage Hot Rod & Design/Pro Machine to make it right. If those names sound familiar, it's because John, Dave Davidson, and the VHRD crew are longtime Bonneville participants and record holders and are behind the first roadster to run over 300 mph on the salt—these guys obviously know how to build horsepower—and they also know how to build an engine tailored to a specific application.
Although Pontiac V-8s have the conventional 90-degree layout, these engines do some unusual features—one was the method of locating the main caps. Rather than registering in a recess machined into the block's bulkheads, the 389 relied on dowel pins to keep the caps positioned correctly. This particular engine was found to have noticeable play between the holes in the caps and the dowels in the block, probably a result of vibration caused by worn main bearings. Left unresolved the result would be a very unstable lower end—bearing, crank, and block damage are distinct possibilities in this situation. The solution was to trim the mating surface of the main caps, bolt them in place, and then fit oversize dowels followed by line honing the main bearing bores.
Another unique feature is the valvetrain. Prior to 1965, Pontiac's stamped steel rocker arms were lubricated by oil delivered through the heads that lead to passages in the rocker studs—holes in the sides of the studs delivered lubricant to the rocker balls. While our heads were 1965s, they did have the drilled studs and as these are the press-in type we opted to install screw-in studs from COMP Cams. Another reason for changing the studs was adjustability. In stock form the rocker arm nuts bottom out on the shouldered stud and are torqued to remain tight—any change in deck height, head thickness, or valve stem height alters rocker arm geometry and there is no way to correct it. The cure is screw in studs with locknuts, and in some cases custom-length pushrods are also required.
With the changes in rocker arm oiling came new head gaskets. Those for 1964 and earlier had a hole for the passage that supplied oil to the galley in the heads to feed the studs. Later gaskets didn't have that hole. When installing 1965 and later heads on an earlier block one common practice was to use a later head gasket without the oil hole. However, many gasket companies have consolidated part numbers, the result being some applications have been expanded so to broaden the application later head gaskets may have the extra hole. In that case another option is to plug the supply hole in the block by drilling and tapping it for a 1/8-inch pipe plug.