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.
L-74. All high comp 400 4bbl medium performance motors from 68 to 70.
L-78 all low comp 400 4 bbl medium performance motors from 1971 to 1979.
L-67 1968, RA1 D port, RAII round port, so where into the round port era now.
L-67 1969 and 70, RA4 motors except in the F body .
These RA4 engines in 1970 got a LS-1 code
L-75 base line 455 engines.
LS-5 1971-72 455 round port HO.
LS-2 455SD.
So the 455SD was in development as early as 1971
The LS-2 U.P.C code is to me the most likely reason for all the number 2 stamping on your heads there.
Note that once engineering got to making a 455SD 16 preproduction casting that they put the air injection boss back in across the top of the exh ports in case they needed to add a air pump to meet emissions.
Here are molds of an Intake and Exh port from a non ported 455SD production head.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!
1) 1940s 100% silver 4 cup tea server set.
Two dry rotted 14 x 10 Micky Thompson slicks.
1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.
Education is what your left with once you forget things!
Last edited by steve25; 10-27-2025 at 05:02 AM.
|