[Burgess]

With all the discussion about block stampings lately, I thought this would be a good time and place to share a couple of interesting ones that I have come across over the years.


The first four pictures are of a 455 block that I pulled from a ’73 Grand Ville. Everything looked normal about the stamping while it was still in the car, although I did notice that the cast date of the block was very early for an 01E car, F142. The 4X heads were cast A063 & A123, the intake was already gone. I was quite surprised to find four bolt mains on this YC, along with both a windage tray and the baffled style oil pan.


After getting the block torn down and somewhat cleaned up, I noticed the stamping area was not normal. It was then easy to see that it had been ground, and when looking at it with a magnifier, I was shocked at what could still be seen. A left over 1972 YE re-stamped as a 1973 YC. The EUN was also removed and apparently changed.


The last picture is a 1970 400 pulled from a full-size car, an Executive I think. An XZ stamping, but over a ground-off spot. The EUN was not changed on this one. Since this is a Quadrajet engine but still equipped with the small valve heads, it was probably changed from YD, the 2 barrel code.


I had already freshened up this nice runner with a new camshaft, lifters and timing set, some 62 heads and painted it before I thought to take a picture of the stamping. It was difficult to get a photo with the re-stamp clearly visible.


I have seen examples of the double-stamped blocks, but has anyone else come across any grind-offs like these?

[Bluesugar]

very good info/input to surmise,..that XZ seems to be quite
questionable under the magnifier;..2-stage epoxy and contorted
stamped letters/numbers set almost get the job done!?

[poncho-mike]

I have found at least two 1973 455s stamped YC that were 4-bolt main. Both were out of Grand Prixs. I believe the cast dates were summer of 1972. I think mine were both July blocks, but I'm not sure. I have never vatted them, so your post got me curious.

I would think that by June 1972, GM would know they weren't building any more 1972 455HO engines, so I have no idea why any of these would be 4-bolt main. If the blocks were several months earlier, you might could make the case for GM making a YE block into a 1973 YC, but production runs are done months in advance.

I remember on one of the YC 4-bolts I picked up that the VIN number looked totally incorrect, the numbers were too big, location wasn't quite right, and it looks like each number was stamped by hand. I thought it might have been an SR block that somebody stamped the VIN into the block during installation, but there was no SR number present. I have no explanation for why either car would have ended up with a 4-bolt main block.

[John V.]

Burgess, pretty interesting finds.

I think the XZ is very easy to figure out. The Engine Manifest Code and EUN were stamped on the block at the Engine Assembly Plant.

It looks like only the area where the Engine Manifest Code was stamped was ground down.

My bet, whoever was stamping the Code got careless and stamped the wrong code. When he realized the mistake, he grabbed the grinder (that he probably had access to for just such a situation), ground off the wrong code and corrected his mistake. The code he stamped initially could have been anything, no reason to believe it was a YD just because they shared same heads. Just as likely that he stamped it as a YZ before realizing his mistake. Conceivable that the guy stamping it only had time to indicate the mistake by some predetermined method and the correction was made somewhere downstream. Either way, my guess is the guy doing that stamping knew that mistakes were an accepted given but was probably told that if he made too many mistakes, he'd be gone!

The restamped YC is a bit trickier. The unknown original EUN adds uncertainty but the June 14, '72 cast date indicates an Engine Assembly that was probably produced in mid to late June as a '72 Engine Assembly.

Since Firebird production was halted in April '72, and since I believe the YE code engine was exclusive to the Firebird, it kinda makes no sense that the Pontiac Engine Assembly Plant would have produced any YE code engines as late as June.

Perhaps there was the possibility of settling the strike around that time and PMD opted to have engines produced with that hope?

Either way I think it is obvious that when PMD determined that they could not (or would not) finish out the '72 'birds after the strike ended, they had lots of parts that they no longer could use. Even as the strike ended, GM announced that many parts would be reused for '73 production although they would be forced to scrap a bunch.

I believe GM could have finished the '72s in process and sold them as new '72s without having to meet '73 mandates for safety and emissions since those rules typically took effect on Jan 1 anyway. I'm guessing GM figured that since '73 Model Year production had already begun, it would have been non-profitable to build a bunch of '72s that would have been viewed as leftovers that would have required deep discounting to move. I guess it was convenient to blame it on not being able to meet new regs than to build a bunch of "old" new cars.

But PMD was not about to throw away good parts, so Engine Assemblies that could be salvaged for major components were probably returned from Norwood and would likely have been torn down to some level and rebuilt as '73 Engine Assemblies at the Pontiac, Mich Engine Assembly Plant, PMD's only Engine Assembly Plant.

Chances are that explains what happened to the YC engine you found. The conversion would have required the original code and EUN to be ground off and the appropriate '73 code and EUN stamped.

I expect hundreds of Firebird '72 Engine Assemblies were transformed in that way. That still makes them rare since PMD produced hundreds of thousands of '73 Engine Assemblies.

The lag time between when the block initially was assembled as part of a '72 Engine Assembly, then disassembled, and finally reassembled as a '73 Engine Assembly around January '73 was likely a result of this being done as "fill-in" work with somewhat low priority.

What you found does make me wonder if the long gone WT code block from my '73 TA which I tossed in a dumpster some time around mid '78 after feeding the carb stud thru it and cracking a cylinder wall might have also been originally assembled using a '72 bottom end. My TA was built in late January '73, EUN unknown. Unless somebody can figure out what landfill it resides in and can find it by excavation, I'm never going to know!

As an afterthought, I will add that there were probably at least some '72 'birds that sat on the line with VIN stamped engines already in place. These engines likely were also pulled out, torn down, and nos. ground off, including the '72 partial VIN to be made part of '73 Engine Assemblies as well.

[poncho-mike]

I believe some short blocks may have been reused by GM. I parted out a very early 73 GTO that had used a YS block with correct 73 top end. I remember finding the build sheet while dismantling the car, and it showed the YS code was correct. I think a 73 GTO should have come with a YT.

Mike

[John V.]

Mike, PMD could not (or at least should not except perhaps unintentionally) have used a '72 code for a '73 application unless the code for the converted Engine Assembly was same/same. The '72 YS was used in the '72 Firebird so conceivably some '72 YS Engine Assemblies that remained at Norwood were shipped back to the Pontiac Plant and converted to '73 YS specs. However, the EUN would have had to have been restamped in any case.

The YS was the standard auto trans '73 GTO early year 400 with points Dist.

YT would have been a fairly rare auto trans '73 GTO early year 400 with points Dist for High Altitude destinations.

Without seeing the stampings, I guess no way to know if it was a '72 converted to a '73 code spec engine as I believe the one Burgess has posted.

But a '73 GTO with a YS would be common and correct.

[poncho-mike]

I may have the codes reversed, and the car had a YT and I thought it should have a YS. I'm going from memory on a car I parted out more than 30 years ago. I remember the manual I was using listed the code in 1972 as a 400 4V, but not in 1973.

[Burgess]

My very first car, a 1972 G/P, had a Y3 code 400 in it. On every chart I've ever seen, Y3 wasn't used until '73. I still have that block, and the build sheet.

[John V.]

Burgess, by chance did your '72 GP have the K65 unitized Dist option?

Years ago I documented a few '72 455 codes that were "missing" from the reference books, some of which pertained to the K65 option.

I did not pursue the 400 at that time, but among the 455 codes I have on my list that were not in the books I knew of at the time were Y4 and Y5.

So I'm guessing there is a legit reason for the '72 Y3, just happens to have been overlooked in references.

[poncho-mike]

I also had an orange 72 GTO with a Y3 400 engine. It was an odd-ball car, bench seat automatic with a/c and an economy rear axle. I bought it from the original owner, power steering, drum brakes, no gauges, and hub caps. When I bought it, I thought the block had been swapped but the VIN checked out. Kinda wish I had kept it, body was super but I just didn't like the white vinyl top.

Mine did not have a unitized distributor, or if it did somebody had removed it. I never ran PHS, but I found the build sheet behind the door.

[Burgess]

John V., I just looked at the build sheet, there is no K65 Unitized Dist shown.
I knew it didn't have one in 1983.

The engine box has Y3 3 in it.

Sched. no. date box has 99 06-02.

Block cast date is E182.

That was an awesome car. Unfortunately, it met it's demise in the late 80's.

On a side note, I found the build sheet behind the door panel, and inside the (original to the car) rear seat back was a mistakenly placed build sheet from a LeMans with the same 99 06-02 in the date box.

[John V.]

I didn't make any notes as to why I researched the '72 Engine Codes or how I discovered the codes I logged. I may have some additional information in a set of binders that I can check when I have some time and if anybody has any interest in discovering more.

According to my notes, I logged the following '72 455 Engine Codes:

YA - B Body Only, auto trans, L75, K65 Dist
YB - A or F Body, auto trans, LS5, K65 Dist
YC - A or G, auto trans, L75, Points Dist
YE - Trans Am Only, auto trans, LS5, Points Dist
Y4 - B Body Only, auto trans, L75, Points Dist (I put a ? by this one, I'm not sure why)
Y5 - G Body Only, auto trans, L75, K65 Dist ( I put a ? by this one, I'm not sure why)
WD - Trans Am Only, manual trans, LS5, Points Dist
WM - A or F Body, manual trans, LS5, K65 Dist

Looking over this list, it occurs to me that the G Body may have used a specific Dist for the auto trans 400 so that the Grand Prix would not have shared the YS (Points Dist) or YT (High Altitude Points Dist) with the A Body and F Body.

However, noting Mike's input about a '72 GTO with a Y3, it is conceivable that the Y3 and some of these other "missing" codes were mid year releases accounting for why they are missing from some of the reference books and replaced the earlier codes for all Model Series'.

Regardless of the reason, I remain certain that the '72 Y3 install was intentional.

[poncho-mike]

I am pretty sure my 72 GTO was also a late year car. It went to a guy in Illinois in the late 80s, who I think still has it in his pole barn.

Of all the cars I've owned and parted out over the years, I have never seen a factory Unitized ignition except at car shows and swap meets. The original distributor was already gone in a couple of 72 T/As I've owned over the years, and was missing from my 72 HO convertible. And I've never found one at a junk yard either.

[John V.]

My '73 TA got the K65 option per the PHS. I think it might have still been in the car when I first owned it '78-'80. I would have known nothing about the unitized dist in those days. All I can remember is that I thought it looked "different" compared to the Delco points dists I was used to. That said, it might also have been swapped already for an HEI cause I also thought I remembered it looking "big" while the unitized would be relatively same size as the points dist.

Long gone when I bought it back last year.

From time to time I've looked at unitized dists on ebay, thinking I might want to have a "correct" dist for it.

But haven't pulled the trigger on one yet.

I'll see if I can find any other info about the '72 Engine Codes in one of my binders tonight and report back.

[Held for Ransom]

Here is the '72 engine chart from the Firebird assembly manual.

The emissions label was 490617 (PU) and updated on paper 3-6-72.

[John V.]

Well there you go. Y3 added along with YT to the F body usage by Rev. dated 2/18/72.

Unfortunately, not enough info to understand the application for it.

And also a mystery code for another 4 bbl 400, p/n 484529 was added to the list on 11/5/71 but then removed on 2/18/72 when the Y3 & YT were added.

I show the YT as for High Altitude application. But no idea if the code removed was for High Altitude and why were 2 codes added and only 1 code removed?

Whatever the removed code, looks like it may have only been in use for a short time.

[Held for Ransom]

I should have added it was the L78 D/WX1 (non-California) (was YS), YS was the California engine (was ZS) and YT was the WT5 (high altitude) engine for the Formula 400/THM 400 lineup.

So, I think that engine 484529 was the first YS engine.

[poncho-mike]

Having dismantled many 70-73 Firebirds, I noticed a lot of oddities occur around the first and the last of the production run. I think one of the oddest was a 12-bolt 3.07 limited slip installed in a very early 1971 Trans Am, automatic with a/c. Driveshafts also seemed to vary a lot, sometimes I would find the 70 1/2 style with the really long yoke, and other times I would find the standard length yoke. I've also found 70 Trans Ams with the small Formula rear sway bar.

[Judge273]

I guessing...but, dismantling a junked car won't produce all factory components...

Oddities in a junker to be expected in that era.

[poncho-mike]

That is normally true, but I took most of the 70-73 Formulas and Trans Ams apart in the 80s. That particular car didn't have many miles on it. It was stored in a small detached garage, and Hurricane Hugo dropped a tree across the roof (1987 or 1988). The 70 T/A automatic I've got listed as a parts car is pretty much 100% original (carb, dist, exh manifolds, etc) as it was dismantled around 1988 or so with 70K original miles. By the 90s, it was pretty hard to find an early T/A to part out.