If you're digging through a swap meet or scouting for parts for a classic GTO build, stumbling onto a set of original pontiac 16 heads is basically like hitting a mini-jackpot. These aren't just old chunks of cast iron; they're a huge part of the muscle car era's DNA. But, as anyone who has spent more than five minutes working on a vintage Poncho knows, things are never as simple as a single part number.
There is actually a bit of a divide when it comes to these specific heads. Depending on who you ask and what year they're looking for, "Number 16s" can mean two very different things. Usually, when people get excited, they're talking about the 1968 version. Those are the ones that helped define the high-performance 400 engines. However, there's also the 1970 version that came on the 455s. Let's break down why these heads matter and how to tell which ones you're actually looking at before you hand over your cash.
The Legendary 1968 D-Port 16s
Back in 1968, Pontiac was at the top of its game. The 400 cubic inch engine was the bread and butter for the GTO and the Firebird 400, and the pontiac 16 heads were the stars of the show. These were D-port heads, meaning the exhaust ports are shaped like a capital 'D'. They were designed for high-performance street use, and they delivered.
What makes the '68 version so sought after is the combination of big valves and a relatively small combustion chamber. We're talking about 2.11-inch intake valves and 1.77-inch exhaust valves. For a factory head from the late sixties, that's a lot of breathing room. The combustion chambers usually measure in at around 72cc to 75cc. On a standard 400 block, that's going to put your compression ratio somewhere north of 10:1. In the days of high-octane leaded gas, that was the recipe for a screamer.
If you find a set of these today, you're looking at a piece of history that still holds its own. They provide excellent flow for a street engine and can be ported to move even more air if you're looking to build something truly rowdy. Just keep in mind that the high compression is a double-edged sword with today's pump gas—but we'll get into that in a bit.
The 1970 Version for the 455
Now, here is where things get a little confusing for the uninitiated. In 1970, Pontiac reused the number 16 casting code, but for a completely different purpose. These pontiac 16 heads were bolted onto the 455 cubic inch engines.
While the '68 heads were all about high compression and high RPMs, the '70 versions were designed for the massive torque of the 455. They still have the big 2.11/1.77 valves, which is great, but the combustion chambers are much larger—usually around 87cc to 90cc.
Why the bigger chamber? Well, a 455 has a much larger displacement, so if you put a tiny 72cc chamber on it, the compression would be so high the engine would probably knock itself to pieces on anything but race fuel. The 1970 #16 heads kept the compression at a more manageable level for the time. For builders today, these are actually quite popular for "stroker" builds where you want to keep the compression low enough to run 91 or 93 octane without a headache.
Identification Tips for the Swap Meet
If you're staring at a greasy set of heads in the back of someone's truck, you need to know what you're looking at. Pontiac was pretty good about casting numbers, but you have to know where to peek. On pontiac 16 heads, the "16" is typically cast right over the center exhaust ports. It's hard to miss once you wipe away the grime.
But since there are two versions, you have to look closer. A quick way to tell the difference without a CC-cup is to look at the date codes. You'll find a code that looks like a letter followed by three numbers (e.g., A128). The letter is the month (A=January, B=February, etc.), the next two digits are the day, and the last digit is the year. If that last digit is an 8, you've got the high-compression 400 heads. If it's a 0, you've got the 455 heads.
Another tell-tale sign is the secondary casting marks. The 1968 heads usually have "72" cast into a small pad near the ends of the head, whereas the 1970 heads often don't have that specific indicator or will have different secondary markings. When in doubt, measuring the chamber volume is the only way to be 100% sure, especially since heads get milled over the decades.
Running These Heads on Modern Pump Gas
This is the big hurdle. If you decide to go with the 1968 pontiac 16 heads on a 400 or 455 build, you have to be very careful with your compression ratio. Most of these heads will put a standard 400 block at roughly 10.5:1 compression. Back in the day, you could pull up to a Sunoco station and get 100+ octane leaded gas. Today? You're lucky to find 93 octane that isn't half ethanol.
To make these heads work on a modern street car, many builders use a dish-top piston. Instead of a flat top, the piston has a little "bowl" or dish in the center that increases the total volume and brings the compression down to a safer 9.2:1 or 9.5:1. This allows you to keep the period-correct look and the great flow of the #16 heads without blowing head gaskets or melting pistons because of detonation.
If you have the 1970 version, you're in much better shape for a 400 build. Those 90cc chambers will actually give you a very pump-gas-friendly compression ratio on a 400, though they might feel a little "lazy" if the compression drops too low (like into the 8:1 range).
Maintenance and Necessary Upgrades
If you're lucky enough to score a set of pontiac 16 heads, don't just bolt them on and hope for the best. These things are over fifty years old. They've lived through thousands of heat cycles and probably sat in a damp garage for twenty years.
First things first: get them pressure tested. Cast iron can crack, especially around the valve seats or in the thin areas of the water jackets. Once you know they're solid, you absolutely have to install hardened valve seats. Original 1960s heads were designed for leaded gasoline. Lead acted as a lubricant for the valves. Without it, the valves can actually "recess" into the head over time, destroying the seal and ruining your performance.
It's also a great time to upgrade the valve springs. Modern camshaft profiles are much more aggressive than what Pontiac was using in 1968. If you try to run a modern Comp Cams or Lunati bumpstick with original 50-year-old springs, you're going to have valve float before you even hit 4,000 RPM. Match your springs to your cam, and your engine will thank you.
Why Enthusiasts Still Love Them
Even with all the modern aluminum heads available today from companies like Edelbrock or Kaufman, many people still insist on using pontiac 16 heads. Part of it is definitely the "cool factor." There is something special about opening the hood and seeing a period-correct engine that looks exactly like it did when it rolled off the assembly line in Pontiac, Michigan.
There's also the "iron head" sound. Aluminum heads tend to dissipate heat differently and can change the acoustic profile of the engine slightly. A high-compression Pontiac with iron heads has a specific, metallic growl that is hard to replicate. Plus, for many racing classes or restoration shows, you have to use a factory casting to stay legal or get those top points.
Final Thoughts on the Number 16s
Whether you're chasing the high-compression '68s for a period-correct GTO or looking for the '70s to build a reliable, torquey 455 cruiser, pontiac 16 heads remain a gold standard in the hobby. They represent a time when engineers were pushing the limits of what a street car could do.
Yes, they require a bit more work than just buying a brand-new set of aftermarket heads. You have to worry about compression ratios, hardened seats, and potential cracks. But for the person who loves the history and the unique character of a vintage Pontiac V8, the effort is well worth it. There's just nothing like the feeling of a wide-track Pontiac pulling hard through the gears, powered by the very same iron that made it a legend in the first place. Keep your eyes peeled at those swap meets—you never know when a pair of 16s might be hiding under a dusty tarp.