The 402 Big Block: C10’s Witness Protection Program

August 29, 2026

The 402 Big Block: C10’s Witness Protection Program

If you opened the hood expecting to see a 396 but found 402 cubic inches staring back at you, Chevrolet wasn't exactly lying to you. But they weren't exactly telling the whole story either. For a brief period in Chevrolet history, the familiar 396 name stuck around even though the engine had grown to 402 cubic inches. Around here, we like to call that the Witness Protection Program.

How the 396 Became a 402

The Chevrolet 396 big block had already built a reputation by the end of the 1960s. It was part of Chevrolet's Mark IV big-block family and had found its way into cars and trucks where buyers wanted something considerably stronger than the typical small-block. Then Chevrolet made a change for the 1970 model year.

The 396 received a slightly larger bore, (0.03) increasing its actual displacement to approximately 402 cubic inches. Technically, the 396 wasn't a 396 anymore. But there was a problem. Everybody already knew the name 396. So Chevrolet didn't immediately throw away all that recognition just because the displacement had changed. In some applications, the 402 continued to be marketed and identified using the familiar 396 designation.

In other words: **New displacement. Old identity. **That's where things get interesting.

Chevrolet's 396-cubic inch Mark IV big block-the engine family that would eventually grow to 402 cubic inches.

Photo: Doug Fawley /Wikimedia Commons - CC BY 3.0

The Big Block Hiding in Plain Sight

Imagine buying a Chevrolet truck during this period. You've got the big-block option. The familiar 396 identification is there. Everything tells you that you're dealing with Chevrolet's well-known 396. Except underneath it all, you've actually got 402 cubic inches. Eventually Chevrolet began identifying the engine by its true displacement, and C10 enthusiasts today generally know it simply as the 402 big block.

But that short identity crisis left us with one of those strange little pieces of Chevrolet truck history that makes these old trucks so much fun to talk about. And if you've spent enough time around C10 people, you already know what happens next. Somebody turns it into a joke.

C10’s Witness Protection Program

A 402 walking around under the name 396? That sounded a lot like an engine trying not to be identified. And that's where the idea for our Forever C10 Witness Protection Program design came from. It's not just another big-block graphic. **You have to know the story to understand the shirt. **That's exactly the kind of apparel we want to make at Forever C10—designs rooted in the trucks, history, parts, terminology and little details that C10 people recognize.

Someone outside the C10 world might look at it and wonder what it means. A C10 owner who knows his big blocks? He gets it.

THE 402 — WITNESS PROTECTION PROGRAM

Originally known by another name.

[SHOP THE 402 WITNESS PROTECTION TEE →]

Why These Little Details Matter

It's easy to look at a classic C10 and see an old Chevrolet pickup.

C10 people see something different.

We notice the grille.

We notice the trim.

We notice the year.

We notice what's under the hood.

And we'll absolutely notice when somebody says they've got a 396 and another guy says, “Well... technically...”

That's part of what keeps these trucks interesting decades later.

The 1960–1987 C10 era wasn't one truck repeated for nearly three decades. Engines changed. Trim packages changed. Body styles changed. Options came and went. Chevrolet experimented, improved things and occasionally left behind oddities like a 402 wearing the identity of a 396. Those details become stories. And those stories are part of C10 culture.