How to identify Pontiac engine blocks


Pontiac blocks are interesting power plants that are often misunderstood and improperly identified by sellers and buyers alike. The blocks of all Pontiac V-8s from the 287 to the 455 are the same size and very close to the same weight, which can make it more difficult to identify the 11 different engine displacements produced from 1955–79. Adding to the confusion, multiple block codes were used, and date codes can overlap up to three decades.

This is a companion discussion topic for the original entry at https://www.hagerty.com/articles-videos/articles/2017/11/27/identify-pontiac-engine-blocks


I am in the process of having the engine in my 1971 Pontiac Grand Prix SJ rebuilt. It is currently at the machine shop. Great timing for this article.


I’m confused by the comments about VIN stamps on the Pontiac blocks.
It is my understanding that for a stretch of years in the 60’s, even for the 67 model year, Pontiac used something they called the EUN: Engine Unit Number. This is a unique serial number for each block. The Billing History Card (furnished by PHS nowadays for a cost) lists the unique EUN of the engine block the car was born with. It’s a 6 digit number at least for 1967. Pontiac did NOT use partial VIN’s in 67 or earlier as far as my understanding goes.
As a side note, they also used a “TUN” number for the automatic transmissions on a small metal tag riveted to the trans case.This “TUN” is also listed on each cars Billing History card.