Pontiac 350 vs Chevy 350 | Pontiac 350 Engine Specs & HP

These days the Chevrolet 350 small block is the Godfather when it comes to historic horsepower. Chevrolet’s first-generation small block has won more races in NASCAR, on the drag strip, and even off-road than any other engine.

But back in the day, the Chevy small block was just one of many different engine designs in General Motors’ stable. Many of the major brands had their own engines, including Oldsmobile, Pontiac and Cadillac. But in the 1970s, GM began standardizing powertrains across its various divisions to reduce production costs and streamline manufacturing. And Chevrolet’s small-block 350 won out as the go-to engine thanks to its reliability, performance potential and ease of interchangeability. This transition was further fueled by the industry-wide push for more standardized, emissions-compliant, and fuel-efficient engines following federal regulations in the 1970s. As a result, the other engines were gradually phased out in favor of the more commonly used Chevrolet version.

In this article, we’re taking a look at the similarities and differences between the Chevrolet 350 and its most performance-oriented cousin, Pontiac’s 350 cubic inch V8. The Oldsmobile and Cadillac engines also had their advantages and unique quirks, but those will have to be discussed on another day.

Pontiac and Chevrolet 350 engines share almost no interchangeable parts. These two V8s have different engine block castings, different head designs and different internal dimensions. As a result, major components cannot be swapped between them. For instance, a Chevy 350 intake manifold will not bolt up to a Pontiac 350, nor will the heads interchange – the bore spacing, water port layout, and bolt pattern are incompatible. The engine mounting points and bellhousing bolt pattern also differ. Pontiac blocks use the famous BOP (Buick, Oldsmobile, Pontiac) bolt pattern, while Chevy blocks use the Chevrolet pattern which has remained constant all the way to the modern LT engine. Unfortunately, that means a swap between makes requires additional adaptations. About the only things you can swap are small items like ignition coils, distributor internals, or spark plugs – and only if they coincidentally happen to be the same style. All significant parts are distinct designs.

It you are scoping out an old Trans Am or Tempest and wondering whether it still has an OEM Pontiac 350 or someone has swapped in a Chevy small block, there are a few visual clues you can easily check for. Both engines place the distributor at the back of the block, but the Pontiac moves it a bit off-center to the passenger side and tilts the distributor a bit back toward the engine’s centerline. The distributor hole is in the block, while in Chevrolets the distributor drops through a boss in the intake manifold. Pontiac’s also have a gap between the intake manifold and the valley of the block and require a separate valley plate to seal it. And if you are under the car, the fuel pump will be on the driver’s side while Chevrolets place it on the passenger side.

Both engines feature an overhead-valve pushrod valvetrain with two valves per cylinder. Both used the relatively new stud-mounted, ball-pivot rocker arms, which were a simpler alternative to shaft-mounted rockers. But in other areas the heads differed. Pontiac 350 heads used wedge combustion chambers and were manufactured with a variety of chamber sizes and valve diameters depending on year and application. The stock 350 engine came with 1.940-inch intake valves, and performance trick is to find high-performance Pontiac heads typically found on larger engines that could have intake valves as large as 2.11-inches for better breathing, but it will also require boring out the cylinders.

Chevy’s 350 heads also used wedge chambers but had their own architecture. Performance versions (e.g. the famed “Fuelie” heads) could have 2.02-inch intake valves, and Chevy offered many aftermarket head options. None of the Pontiac’s head components interchange with a Chevrolet 350 thanks to different bolt patterns and cooling layouts. Internally, Pontiac 350s typically had heavier crankshafts and overall, the Pontiac was a beefier engine. It’s taller deck block showed some big-block DNA, while the Chevy 350 was a leaner small-block optimized for efficiency and flexibility.

When it made its debut in 1968, the Pontiac 350 came equipped with a two-barrel carburetor and made 265 horsepower. Pontiac also offered a high-output version in 1968 and 1969 with a 4-barrel carb and hotter cam that helped it make 325 horsepower. This was pretty impressive for its size, after all the Pontiac 400 was only worth five more at 300 horsepower that year.

Thanks to its relatively long stroke, the Pontiac 350 also delivered solid mid-range torque, so the 350 was a good performer for Pontiac, which staked its name on affordable performance. The Chevrolet 350 had an even wider performance envelope. It first appeared as a 295-horsepower high-performance option in the 1967 Camaro. By 1970 Chevrolet offered the 350 LT-1 V8 rated at 370 horsepower and 380 lb/ft of torque in the Camaro Z/28 and Corvette. This small-block could rev over 6000 RPM with its free-breathing heads and high-lift solid cam, something the Pontiac 350 was less inclined to do thanks to its heavier rotating assembly. In everyday tune (4-barrel, 9:1 compression), both engines produced around 250–300 horsepower in late-1960s sedans.

Of course, both engines only got better as the years went by -- at least until unleaded fuel requirements and smog regulations threw a big wet towel on all the fun. During the muscle car era of late ’60s, both engines sported high compression ratios (often 10.25:1 to as high as 11:1 in Chevy’s LT-1) on performance models to help maximize output. However, by the mid-70s GM had choked off those numbers thanks to lowered compression ratios and added emissions controls.

Both the Pontiac and Chevy 350 saw their power ratings drop significantly thanks to those requirements as well as dyno numbers switching to SAE net. For instance, by the mid-1970s the Pontiac 350 was down to around 155 horsepower, and the Chevy 350 was wheezing anywhere between 145 and 175 horsepower depending on the vehicle.

The Pontiac 350’s last performance hurrah was essentially the 1969 H.O., as Pontiac shifted focus to its larger 400 and 455 engines for muscle cars. Chevy, on the other hand, continued to develop performance small blocks. Even in the late ’70s and ’80s, the 350 served in Corvettes and Camaros with improvements that helped both power and longevity while still meeting smog requirements.

In terms of character, the Pontiac 350 delivered plenty of low-end and mid-range torque, making for strong acceleration at modest RPM. The Chevy 350, especially in high-performance trim, could rev higher and generally had a broader high-RPM power band. Both engines could be modified for more power, but the small-block Chevy’s massive aftermarket support makes it easy to dial in serious 350 sbc horsepower using proven build recipes and off-the-shelf parts. Pontiac 350s can be built to perform as well, but builders often swap in a longer-stroke crank to make a 455 since the blocks are dimensionally the same and respond better to performance mods.

The Pontiac block’s greater mass gave it high strength and room for increased displacement, but it was overbuilt for 350 cubic inches, which meant adding unnecessary weight in a smaller car. By contrast, the Chevrolet 350 was a true small-block design, making it more compact and lighter. That’s why so many original Pontiac 350s have been converted to a high-displacement version over the years. It’s the best way to overcome the disadvantages of the heavier block.