100/4 Headlight Gaskets

by Roger Moment

Originally published in the Austin-Healey Magazine, January 1990

This is the start of a story about one of those parts that you rarely even think about, or if you did, would hardly give much attention to. Furthermore, it only concerns the 100/4 model Healeys, the BN1 and BN2 P1 Mounting using 555415 series.

So why care? For one reason, it is a good example of how parts were substituted without necessarily following what was predominantly used. In this case, the substitution results in a small, but noticeable (particularly after you've read this article) decrease in attractiveness. And second, this article is a request to owners of these cars, especially original cars, to check this detail so that we can document, and better understand the full duration of the part's use. The part in question is the gasket that is used between the headlight bowl and the body of the 100/4s.

The first picture on page 9 shows, on the left the commonly available replacement gasket and on the right, a wider gasket, the one originally furnished on BN1L/223867 (completed in July, 1955). Picture B shows a close up of two cross-sections of the wider gasket. Identical wide gaskets have been found on BN1L/225762 completed in May. 1955 (why the earlier-built car has a higher serial number is a puzzle, and the subject for another article at another time) and on BN2L 228497, completed around September. 1955. From these pictures, you can see that the wide gasket has an angled lip that, in effect, fills the gap between the chrome headlight ring and the body panels.

The common replacement part is cut basically like that used on all six-cylinder cars. having as quared-off edge and rectangular cross-section. The face shown in these photographs is the back surface, the one that presses against the body. Numbers cast into the wide gasket are 555415 and TM401. In checking old Lucas parts books, this number is not listed for the Austin-Healey 100/4 but does show up for the 1956 Hillman Minx, the 1956 Sunbeam Saloon MkIII, the 1957-59 2.4 Jaguar, and the 1957-60 Morris Minor.

The number cast into the narrow gasket is 554280, which is listed for the Austin-Healey 100/4. Furthermore, if you look at the Austin-Healey parts books, the numbers given for the headlamp gasket (none are Lucas numbers) are: 100/4 BNI&BN2 17H 5416 100/6 BN6 3H993 3000 Mk I BN7 & BT7 13H349 17H5214 57H5456 3000 MkIII BJ8 57H5457. So, while the AH parts book does list several different parts numbers for the 100/6s and 3000s. it only lists one number for the 100/4. When used on the car, the wide gasket does improve appearance of the headlight fit. The diameter of the flat body surface to which the bowls are mounted is about 3/8 to 1/2 inch larger than that of the chrome rim. Consequently, as shown on page 9, a rather unfinished looking gap and step is left the narrower common replacement gasket (554280) is used. However, the wider, angled gasket (555415) successfully hides this manufacturing "imperfection" resulting in a nicely finished transition, as shown on page 9.

Available published photographs of 100/4s, taken in the period 1953-1956, are few in number and not of sufficient quality to adequately show this detail. From those that I have seen, and perhaps the clearest is of the Florida Green BN2s, shown on page 25 of John Wheatley's Super Profile Series book on the 100/ 4, the gaskets used appear to be the narrower, rectangular cross-section more like that of the common replacement part, 554280. p2 Special gasket #555415 is on the right side of the photo at the far left. The "common replacement" gasket is on the left side of the photo. P3 The photo at the immediate left shows a closeup of the cross section detail. P4

The photo to the lower left is a closeup of the headlight mounting using the "common replacement" gasket. P5 The photo below is a closeup of the #555415 gasket installed. The fact remains that there are at least four documented examples of where the wider, angled gasket (555415) was used (the three cars noted above plus one other from a car having a chassis number in the series 225xxx, and all are late BN1 or early BN2 cars built in 1955. Nevertheless. this gasket's part number does not appear in the Lucas parts manual. The questions arise: Was there a change-over to the wider gasket, and if so, when were the beginning and ending points of its use? Or was this part simply supplied by Lucas inadvertently with some particular shipments of head-lamps and used just because it fitted and was available? Is it possible that the part that was supposed to be used was a poorer fit than one that was never intended for use on the Healey, or was the substitution made and never reflected in the parts books or made available as a replacement part?

At present, I do doubt that the wide gasket, part 555415, would have been installed as a replacement item, so any car having this style probably came with it from the factory. To help answer these questions, I would appreciate it if people having gaskets that are known to be original would check them to see what style they are. and drop me a card (1895 Lehigh Street, Boulder, CO 80303) with their chassis number (BN1L/xxxxxx or BN2L/xxxxxx and the style of gasket (narrow and rectangular or wide and angled).

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