PART NO.  SPL.PAGE  DESCRIPTION                                                           
ACA5127   15.D.3    Screw -tank unit to tank (6) -(fuel tank, 1500) -changed to ARG923 -
	during 1600 production
ACA5127   16.D.3    Screw -tank unit to tank (6) -(fuel tank, 1600) -changed to ARG923 -
	during 1600 production
ACA5127   TC.D.3    Screw -tank unit to tank (6) -(fuel tank, Twin Cam)
ARG923    16.D.3    Screw -tank unit to tank (6) -(fuel tank, 1600) -was ACA5127

ACA5127 Hex Head Screw used on MGA 1500

ARG923 Slotted Pan Head Screw Used on MGA 1600 These are all originally #3BA x 1/2 (34.8 TPI)

These screws began as ACA5127 Slotted Hex Head Screw for MGA 1500.
Changed to ARG923 Slotted Pan Head Screw for MGA 1600.

Superseded by 53K165 Phillips Round Head Screw (after end of production)
This number 53K165 does not appear in any MGA Service Parts List, so you do not get any picture of the part that was only used after production was finished.

-Moss Motors USA number 323-030 -- may be
#8-32-UNC (common) or #8-36-UNF (more rare). Both are incorrect threads.

The reason Quantity is 6 in the SPL is because the four screws securing the rectangular cover are part of the sender unit assembly (not normally sold separately) , while the six screws specified are used to mount the sender unit onto the fuel tank. (And don't forget the mounting gasket).

On 3/15/2024, Bruce Hopgood in Montreal, Quebec, Canada wrote:
"Fasteners are a peeve of mine, and I really like to have these correct, no matter how banal the application. I thought I might share this with you. --- I am sorting a fuel tank, not a MGA unit but a direct contemporary. The car uses a same/similar sender unit. The vehicle SPL calls up the screws to hold the sender unit to the tank as #ARG923. The screws are a Hex Head, slot measure 1/4" across flats, and 0.600 long. A #8-32 nut threads on but is loose . Could this thread be BA?

"Apparently, vendors are not as precise as we would like. I did order some replacement screws #ARG923 from a UK vendor. I received a correct length, thread into the tank fine however have a Phillips POZIDRIV raised/round head. These replacement screws also thread into the tank well, and a 8-32 nut spins on fine. -- Curious how the original part number ARG reference has morphed". -- Bruce

Comments from Barney:
First, Phillips and POZIDRIV are different slot designs requiring different screw driver tools (but that's not the issue here).

I will go out on a limb here with an educated guess. I am inclined to believe that the MGA fuel tank and sender unit may fall into a certain class with some "non-MG" part suppliers in early post-war period. Think Auster, Austin, Lucas, Smiths/Jaeger, and SU. These "other" companies may not have been so eager to jump on the Unified thread standard, and continued producing components with other threads, Whitworth, BA, BSF, BSPP. This applies in particular to products that may have pre-war heritage continuing with only minor design changes in post-war period.

This leads me to believe that these threads in the MGA fuel tank were originally 3BA threads, 0.161" major diameter, 34.8 threads per inch, and 47.5 degree thread angle. A #8-32-UNC (or #8-36-UNF) thread is 0.003" larger major diameter, with less deep 60 degree thread angle. The very slightly larger #8 nut, being relatively thin, will screw right onto a 3BA screw, just a little loose. A #8 screw will not easily thread into a 3BA tapped hole. But the fit is close enough that someone may think it is just a "dirty" thread. If you run a #8 tap through the 2BA hole, the female thread will clean up enough to accept the #8 screw.

Those not so well informed may never know the difference. These days some parts suppliers may be offering #8 screws for these applications without ever mentioning that they are not original spec parts. So you may well just "clean out" the female threads and use the #8 screws.

The problem here is that if you subsequently try to install original issue 3BA screws into holes that have been cleaned out to #8 female threads, the 3BA screws will fit more loosely and may be at some increased risk of leaking or stripping out with too much torque. So if a #8 screw works easily in your fuel tank, then continue to use #8 screws, do not go back to the 3BA screws.

Addendum, October 2026:
Another Faulty Replacement Parts problem just popped up. Recent new issue MGA fuel tanks in standard volume (nominal 12-gallon tanks) from Moss Motors may have faulty welding for the sender unit attachment ring. these have been spot welded to the outside of the tank, and the spot welds were too hot and/or too long in duration, so the spot welds have burned through the tank end plate. This allows fuel to leak through the end plate to escape from behind the ring. No gasket can seal the thin gaps behind the ring. Some people have tried hand painting multiple coats of fuel tank sealer inside the tank behind the area of the ring, trying to seal the burn-through holes. J-B Weld smeared inside might also work. No final reports yet.