Some Technical Details on the 1972 Y Code GTO and LeMans

                                                                          By: Patrick Smith

   The bulk of articles relating to 1972 GTO 455 engines deals with the 455 HO round port version; rightly so as it was a real scorcher of an engine. There is little to no data on the 455 D port engine so I thought I'd establish a page that covers what the pieces are for this engine. It will be handy for those trying to document and restore one of these rare flyers. By the way, these codes and numbers apply to the Luxury LeMans Y codes as well. So if anyone owns a 1972 D port 455Luxury MeLans, give us a visit!
 Engine Block: casting number is one of the last good ones, using the 485428 number. It is a two bolt main block although some units may be drilled for four bolt use, they will have 2 bolt main bearing caps. This block casting was used from 1972-1974. Starting in 1975 Pontiac switched to a new casting number, 500813 and that is what appeared in 1975-76 Trans Am 455 HO engines.
Service Replacement (SR) blocks. Occasionally you may encounter an engine without a VIN number and with SR stamped in it. These were service replacement blocks assembled for warranty purposes and some came with metal tags stating it is a warranty replaced block. The suffix code for the D port 455 engine with auto trans is YK.

One of 235 made. How many have survived? Is yours one of them?

Cylinder Heads: The D port 455 heads used on Y code engines are 7M5 castings. They used 1.96/1.77 intake and exhaust valves and had a spacious,114 cc chamber.The part number is 485075.

Carburetors:  The carb is a Rochester Quadrajet 4 barrel unit. Strangely enough, there are 4 variants for the Y code 455 engine! The most common would be the 49 State emissions carb, 7042272. A California State emission carb is 7042262. There were also two separate High Altitude carbs for the Y code 455 engine. Due to the low numbers of cars made, there may not have been Y codes produced for high altitude States. The part numbers are; 7042278 and 7042276. All are automatic transmission units with center fuel inlet. They can be made by Rochester or Carter division under license by Rochester.

There are 4 different carb numbers for the Automatic D port 455. Two of which are JHigh Alt versions and 1 California emission version. Due to low production totals, it's possible the High Alt carbs were service replacements only.

   

Transmission:  Only one transmission was used on Y code cars, the Turbohydramatic 400 three speed unit. UPC code is M40, transmission suffix code on metal tag is PY. It is a heavy duty version of the TH400.

Carrier Codes: The Y code GTO and LeMans used the Chevrolet 12 bolt carrier. It is a series 2 version with a 3.31 axle on non air conditioned cars or 3.07 on air conditioned cars. Safe T Track limited differential was optional for this carrier. The unit will also have upper control arms leading from the axle to the rear carrier support part of the frame which was a 455 drive train specific assembly.
The carrier suffix codes for the Y code cars are as follows:
Safe T Track non a/c 3.31 = XU open differential non a/c 3.31= WU
Safe T Track        a/c  3.07= WT open differential      a/c  3.07 = XT

Frame Codes: The 455 engine LeMans and GTOs had their own frame due to rear axle and engine requirements. There were two variations; the open channel regular frame or boxed HD or convertible frame. The open channel 455 frame was coded XU 40 for the automatic transmission.  The boxed frame was coded XV. We have found that most often on build sheets that the frame code for automatic 455 LeMans and GTOs have XU 40 on them. There is a Heavy Duty boxed frame or convertible frame version, coded XV. You will only encounter this frame on GTOs ordered with the heavy duty frame option. No convertible GTOs were made in 1972. However, it's possible for a LeMans Y code convertible to exist and have this frame. It should indeed have it.  The frame part number is 483709 for the 455 powered GTO/LeMans series. It has the unique motor mounts up front and special upper control arm to 12 bolt braces in the rear.

This is the correct location for 455 Pontiac engine mounts.

boxed frame, also convertible LeMans Sport 455:XV
open frame  GTO/LeMans 455                            :XU (sometimes XU 40 on build sheets)

Early Build vs Later Build Cars: Some legislative changes altered the product mix on 1972 LeMans and GTOs. The new safety standards for cars made manufacturers delete the chrome rear view mirror assembly in favor of a black camera case finish mirror housing, Early build car from December and back usually used chrome housing assemblies. The speedometer was also changed from 140 mph to 120 mph starting in January 1972, The newer speedo also has a lamp for seat belt warning. There is the whole issue of batch build and build out cars which has been addressed in certain articles I penned. This is an ongoing research issue. My car built in Pontiac in the last week of May, received 1971 GTO tail lamps. I switched them to smooth units. Some cars came with LeMans grilles complete with Pontiac arrowhead when GTO grilles were supposed to be used.
   * Article (c) 2015 by Patrick Smith. Images by PHS MEDIA ARCHIVES

New Addition: 1972 Y code GTO hardtop

                                                                      By: Patrick Smith

Note two indents for 1972 hood and the silver grilles plus surrounds. This is likely an
unmolested front end. Can't say that about the interior or drive train however.

         

This car helps solidify our info on appearance of Y code GTOs. Notice no die cast emblems used near side marker lens?
This is very likely an original front end as the hood has the twin indents found only in 1972.

  Well it's been an exciting day with a new addition to the registry of Y code LeMans and GTOs. I found a listing online for a Cardinal Red 1972 hardtop GTO. This one is interesting as it's an Atlanta Georgia built and sold car that was discovered in a field in northern Georgia by the seller, Mr, Seidler.  I have to tell you up front; she's a project car. The original engine and rear axle are missing. The car has seen a fair bit of abuse including some racing I suspect due to the missing items from the interior and addition of go fast goodies. Let's start looking her over.
 

This door vin tag shows an April date while cowl tag shows last week in March build for the body.
Notice how the gross vehicle weights were added on this tag? This isn't seen on cars from other plants.

  We are presented with a complete body with front end intact. Missing T 41s are a real problem on these cars because the fenders and hood are one year only items! You can use a 1971 hood on a 72. No problems there, but the 71 hood has one cut out for finger release while the 72 has two. The 72 fenders have side vents while the 71s are solid. A look at the cowl tag reveals it was built in Atlanta during the fourth week of March. The trim code is 256 which is black bench seat Morrokide vinyl. Another RPO code appears on the tag indicating A52 for bench seats.  The paint code is 75 75 for Cardinal Red paint upper and lower. Also notice on the Atlanta cowl tag they present some RPO codes as they relate to the body such as M40 for automatic transmission.

Here is our first indication that the car has been altered a bit since new. Notice the tilt steering column with no sign of
a column shift pawl? The cowl tag and base door panel indicates a bench seat car so column shift was factory. The pedals do not indicate a clutch car. 

   As for options, well the seller did not present a PHS document but since we have the VIN number, anyone can phone Jim Mattison and ask for a PHS package, If you're serious about chasing down a Y code this is well worth doing. I can tell you some of the options on this car from deducing from pics, but any car this old and having gone through a number of owners may have been altered significantly. What I can see so far is this was an air conditioned car at one time. The firewall has been hacked and metal added where the POA and receiver dryer was. Those trio gauges added to the dashboard seem to be filling a pre cut hole where the ac vent would be. Other items the car came with include an electric clock, pedal dress up, radio, chrome driver side mirror and rocker guards. Alas a lot of pieces are missing so this is as far as I can safely deduce. The a/c is a sure bet though because if you look in the rear seat area the plastic shroud covering the space between the grille and rad cradle is present and this was only found on a/c cars.
    

Here we can see the cowl tag indicating black Morrokide bench seat, Cardinal Red paint and a number of options including
automatic transmission. The base interior had no pull straps but did include the GTO emblem from 1971.

   Notice there is no 455 CID call out on the rear quarter panels. I did notice however that the GTO emblem is in fact, painted on this car which makes me wonder if the car was repainted at one time?
The grilles show the silver color that GTOs came from the factory at the time. A lot of cars have been restored with black finish grilles which is only correct for a 1971 Judge. The grille surrounds and actual grilles are silver. If you look at the front of the hood, you can also see the two indents found only on 1972 hoods. Clearly this front end wasn't changed.
    

That plastic panel you see is used only on A/C cars.

No sign of 455 CID decal but the GTO thing is painted on. Likely it was repainted.

Car is rusty but more or less savable. 

  Condition wise, this is a real fixer upper. It has an automatic transmission but the seller didn't check to see if it was numbers matching. So missing engine and rear carrier, possibly missing original transmission makes it a street machine for restoring. If someone finds the original block and tranny, they've got something nice to build up. Although a fair bit of rust appears on the trunk lid and quarter panels, the rest of the car seems decent. Notice the use of proper 1972 tail lamp bezels on this car. It appears the build out phase hadn't hit Atlanta yet in March. My car by contrast, had 1971 tail lamps and quite a few others have been assembled that way earlier in the year. Also observe the lack of stainless steel trim on the tail lamp bezels. This is correct for 1972. They were painted matte silver new and this wore off in a few years.The current high bid for this car is at $4,500 dollars. We will keep tabs on it and report back if and when it sells. Meanwhile it has been added to the registry post. Latest check shows it is still listed online with different organisations and is in Ranger, GA.
   * Article (c) 2015 by Patrick Smith. Images by PHS MEDIA ARCHIVES.