If you’ve followed my past blog posts or read my articles over the years, you’ve likely recognized how much I sincerely enjoy Pontiac “numbers.” Whether its finding production numbers for a given model year or application, seeking out minute casting differences, or determining just what separates similar components with different casting/part numbers, I find solving such mysteries thrilling.
I received an email from Chris Courter asking to help identify this otherwise typical number-485428 455 block that Pontiac used from 1971 to 1974.
A few days ago, I received an email from Chris Courter of Charlotte, North Carolina. He was asking for help identifying a code-ZE 455 block that recently came into his possession. He described it as a typical number-485428 casting with 4-bolt main caps, an Engine Serial Number (or ESN) of 515897, a VIN stamp from a 1973 Firebird, and a cast date of June 14, 1972.
The F142 cast date on Chris’ block indicates it was produced on June 14, 1972. The pointer tells us that it occurred during the night shift. Although June 1972 was a long way from middle of the 1973 model year, casting dates can occasionally vary widely from vehicle production dates.
He added, “Someone had ground off one of the stampings using what appears to be an angle grinder and restamped the engine code to ‘ZE.’ Underneath I can clearly see a "W" but I'm not sure what the second letter was, although I can tell that it’s straight up and down on its left side. I'm thinking it might have been an ‘M’ or a ‘D.’ Any thoughts on why someone might do this?”
As you might imagine, I was intrigued by its re-stamping. “ZE” wasn’t necessarily a rare code and if it were someone’s attempting at forgery, could they be so careless to leave behind obvious evidence that it was re-stamped? Thinking not, I immediately began playing out different scenarios in my mind that might cause Pontiac to re-stamp an engine application code.
The “55” casting in the valley is further proof that Chris’ block was a 455-ci.
I explained to Chris that to me it sounded like a basic 1973 d-port 455-ci, that the VIN confirmed it was originally installed into a Formula or Trans Am built at Norwood, and that based on the “ZE” coding, it was originally backed by a manual transmission and equipped with a Unitized distributor.
Chris’ block was originally equipped with 4-bolt main caps. While it’s not unheard of to find a standard-performance 455-ci of the era equipped with 4-bolt caps, it’s certainly unusual.
While practically all 455-ci blocks produced from 1970 to 1974 were drilled and tapped to accept 4-bolt main caps on the center three journals, the 4-bolt caps themselves were largely relegated to the high-performance 455s during those years. I have, however, documented a handful of standard-performance 455s of the era originally equipped with 4-bolt caps. Those instances are quite rare and seemingly occurred in production without reason. I suggested that Chris’ 455-ci was one of the lucky few that received them.
You may recall that Pontiac had its hand slapped by the EPA during the 1973 model year for using what the EPA termed as a “defeat device.” It consisted of a timer that rendered the emissions control system inoperable after a specific amount of time, which just happen to be a few ticks longer than duration of the EPA’s test. The EPA forced Pontiac to recertify all its engines by mid-March 1973. According to bulletin 73-T-21A, dated May 10, 1973 Pontiac’s second-type emission system reached production on March 15, 1973 with ESN 532727. Pontiac assigned all new engine codes to differentiate late-1973 engines from their early year counterparts and painted them a darker shade of blue to boot.
The 455’s VIN stamp of 23N127XXX tells us that it was originally installed into a Norwood-built 1973 Firebird Formula or Trans Am. The last few digits were blurred for security purposes.
I told Chris that “ZE” was a late-1973 code and that its corresponding code for that same application with the early emissions system was WT. I asked if it were possible that what he was seeing was once a “T?” His reply included images of the block and as I looked them over carefully, I could clearly see the remnants of the “W” beneath the “ZE” and surmised that the visible vertical line of the second letter was once been a “T.”
Chris, however, was convinced otherwise. His note back read, “I really think that is a ‘D’ after the ‘W’ as I can see two pieces of the leftover vertical leftmost part of the ‘D.’ So I'm pretty sure it was ‘WD.’” He then asked if there could have been any correlation to the WD-code used to identify the round-port 455 H.O. during the 1972 model year.” That’s when it hit me!
The block was stamped “ZE,” which codes out to a 1973 Firebird 455 with manual transmission, Unitized ignition, and second-type emissions system. It’s quite obvious that someone haphazardly ground away the block’s original application stamp. If you look closely at the “ZE” you’ll see the remnants of a “W” between them. Chris believes the second character was originally a “D.”
Upon considering the June 1972 cast date of Chris’ block, the 4-bolt main caps, and the WD code that was replaced by “ZE”, I strongly believe what Chris owns is a recycled 455-ci block from the 1972 model year. Why would Pontiac recycle a “used” block to create a new production engine? I feel that answer lies in what occurred at the Norwood, Ohio assembly plant around that same time.
Firebird production (as well as Camaro and X-car) at Norwood came to a halt on April 7, 1972 when the UAW went on strike citing poor working conditions. Based on the June 1972 cast date of Chris’ block, it seems that Pontiac continued building Firebird engines during the strike period, most likely to ensure that vehicle build orders were covered once the strike was resolved and production resumed.
The 174-day strike at Norwood, Ohio began on April 7, 1972 and wiped out the remainder of the 1972 Firebird model year. Cars and equipment laid in state on the assembly line while negotiators fought to reach an agreement. Firebird engine production at Pontiac’s Plant 9 appears to have continued though.
Weeks turned into months as local negotiators from both sides attempted to reach an agreement. It wasn’t until discussion was taken up on a national level in Detroit that a mutual agreement was reached in September 1972. By that point the 1972 model year had ended, however, and the 1973 model year was well underway.
When workers walked out in April, they left behind a plant full of vehicles in various states of assembly and an inventory of parts and material in which to build them from. Since the partially-assembled Firebirds on the Norwood line could not meet new bumper standards for the 1973 model year, virtually everything on the line had to be scrapped when production resumed in October 1972.
Pontiac issued Car Distribution Bulletin 72-76 on August 30, 1972 officially canceling what remained of the 1972 Firebird production schedule.
It appears that there must’ve been a cache of fully-assembled Pontiac V8s destined for 1972 Firebirds setting somewhere—whether at Norwood or Pontiac’s home plant. The 1973 model year also saw new emissions regulations, which meant new cylinder heads, intake manifolds, and carburetors. The cache of otherwise-new 1972 engines were virtually unusable. Based on Chris’ example and his sleuthing assistance, we, as a hobby might understand that—at least some instances—Pontiac disassembled some 1972 engines to re-purpose their short blocks and combined them with new 1973-spec top ends, and stamped them accordingly. It is coincidental that Chris’ 455 was originally installed a similar Firebird-only application the following model year? We may never know that answer.
It’s presently unclear the significance of the “936” stamped onto the front of Chris’ 455. It might possibly some sort of identifier that signified a sequence during the repurposing process.
The only perplexing point is the ESN of Chris’ ZE-coded block. Its 515897 occurs come 16,800 units before Pontiac’s noted emission system ESN break point. Pontiac wrote in bulletin 73-T-21A that approximately 700 early engines were updated to include the late emissions system and were painted the darker shade of blue, but it doesn’t say if the early coded blocks were re-stamped with late coding. While this ZE-coded 455 may be one of those lucky 700, it’s also possible that its 515897 ESN is representative of its sequential build number during the 1972 model year.
Does Engine Serial Number 515897 signify its sequence when it was first assembled in 1972 or reassembled in 1973? I’d guess the latter, but “ZE” is a second-type 1973 emissions system engine code. According to Pontiac documents, the second-type system reached production with ESN 532727. Your guess is as good as mine!
I’m confident that with the help of Chris’ keen eye and wondering mind that we’ve successfully proven that Pontiac kept building Firebird engines for at least some time during the Norwood strike and that at least one short block was re-stamped for use in a 1973 model year vehicle.
Have you ever seen any interesting block stampings? I’d love to hear about and/or see your example(s)!