[unruhjonny]

Originally Posted by steve25

Pontiac engineering U.P.C codes tell the progression of engine development and the time span of usage in many cases.

The code only changed when significant changes were done for the most part.

A few brief examples.

(removed)

LS-5 1971-72 455 round port HO.

LS-2 455SD.

...

my understanding is that RPO/UPC codes were reused, and issued by the parent company - not necessarily a divisional thing;
As an example a 1969 Chevelle could have been ordered with an L78, and so could a same year GTO;
In the case of the GTO it was the ‘base’ 400/4bbl engine - for the Chevelle it was much more special.

Here is my correction of the engine codes which Pontiac used, and what I removed from above:

L-30: 350/2bb 1968-1977

L-65: 350HO 1968/69; 350/4bbl 1974-1977; best 350 you could get for the given year

L-67: 400 ‘Ram Air’; 1967-1968.5 ‘D-port’; 1968.5-1970 ‘round-port’; the best 400 you could get for the given year

L-74: 400HO 1967-1969(?); “RAIII” 1969-1970; one step down from the L-67

L-75: 455/4bbl 1970-1976; “bread and butter” 455 performance engine for which ever model year

L-78: 400/4bbl 1967-1979; “bread and butter” 400 performance engine for which ever model year

LS1; (purported) RAIV-SD 1970; did not pass pre-production stage.