As Tri-Power 389s go, this one has about as good a story as they come. It was factory equipped in a new ’65 GTO sold through the legendary Royal Pontiac in Royal Oak, Michigan, just a couple blocks away from Detroit metro’s famous Woodward Avenue. (Though it was sold through Royal Pontiac, it did not receive the Bobcat package.) The GTO took its place in the Tiemann family driveway in May 1965 as a family car, hauling around Mr. and Mrs. Tiemann and their young son, Scott, who would later become one of the world’s foremost Pontiac restorers, and a judge with the GTO Association of America.
In the 1970s, Scott removed the GTO’s 389, replaced it with a big-cube 455, and went racing. Fortunately the 389 was removed intact and stored. When it came time to restore the family ride, Scott retrieved the well-preserved engine, had it rebuilt, and then detailed it with the meticulous attention to detail he is known for in the Pontiac hobby. “My goal is absolute authenticity. Every nut, bolt, and clip, as far as I’m aware, is absolutely on the money,” Scott tells us.
Just before the 389 was installed back into the 1965 GTO, HPP’s cameras were allowed in for a look at what goes into making a classic, show-stopping ’65 GTO Tri-Power engine a sight to behold.
There’s so much show-ready detailing on this engine, it’s going to take two parts to show it all. Do you want to make your 389 stand out from the crowd? Let’s get started.
When it came time to restore the family ride, Scott retrieved the well-preserved engine
Let’s get right into the heart of the matter—the trio of Rochester two-barrels, correctly plated by Woodruff Carburetor Restoration and cleaner than a hospital room. The throttle-return spring is NOS. Examined up close, the spring’s paint is spotty. Scott says, “It’s an NOS spring right out of the package so I left it just like it was.” The front carb has a vacuum port used with an automatic transmission, but it’s capped for manual transmissions. The cap is also an original, identified by its squared end, and not rounded like modern reproductions. Behind the center carb is another vacuum port; this one taps into the manifold, and connects to the distributor-advance diaphragm via a black-with-green-stripe hose. The short black hose running vertically from the intake manifold to the top of the center carb is one of two—one to each plane of the manifold. They are part of the PCV system. Both hoses are stamped GAS; the longer hose is in larger letters.
Carburetor-base nuts are bright silver, not plated or painted, and, common mistake here, there are no washers under the carb nuts. Studs are engine color. Regarding the plating of the carburetor bodies, Scott says, “These don’t all exactly match, I think because the different pieces take the plating differently. Some guys will get them real bright, but I like them to be subdued. I think it’s authentic like that.” Here are some other details—the carburetor-top screws are black zinc, the fuel lines are aluminum with brass fittings, and the tan gaskets beneath the breathers are NOS.
This brass 90-degree adapter is tapped into the rear of the front carburetor, and acts as a vacuum source for the optional power-brake booster. Since this car did not come with power brakes, the original fitting is capped off with a bright silver screw. “The fittings the aftermarket sells now are bigger and heavier,” says Scott.
AC Logo Air Filter
Original breathers are nearly extinct. They were a gray foam stamped with the AC logo and some other branding, but the foam turned to mush or powder over the years, so the best thing we have today are these earlier reproductions with logos. Current reproductions do not have the logos, so restorers just have to do the best they can. Breather bases are gloss black, not the popular semi-gloss. “ACDelco made all that stuff and it’s shiny,” notes Scott. “The original bases are steel; current reproductions are aluminum.”
Front and Rear Carburetor Levers
The linkage connects to the outboard carburetor levers. The outboard carburetors are interchangeable, but the levers are specific to the front and rear. The rear carburetor has a small hole in the lever where linkage for a vacuum diaphragm would connect on cars equipped with automatic transmissions. To accommodate the extra thickness of the diaphragm’s mounting plate, the studs for the carburetor are a little longer on the passenger side. This hole is on the rear carburetor only, and not on the front one.
The crankcase breather is on the passenger-side valve cover. Reproductions are commonly av
The crankcase breather is on the passenger-side valve cover. Reproductions are commonly available, but this one is NOS. The OEM breather has a series of crimps at the base (arrows); reproductions don’t.
Valve-Cover Bolt, Dipstick
All fasteners on this engine are from a 30,000-mile LeMans also built at the Pontiac, Michigan, plant very close to the same time as the GTO. Scott makes a small deviation from pure stock to the flange-head valve-cover bolts in the interest of preventing corrosion. “In the late ’60s, Pontiac began plating the bolts, but these early ones had an as-manufactured finish. Rather than leaving them bare, I put black zinc on them so they’ll stay dark and not corrode.” The dipstick tube and handle are solid blue, without chrome or other color anywhere on them.