Dunlop rear disc from the above car, which was originally registered to Frank Muir, famous wit and raconteur
Press Release!

To read the 1957 press release with details of the specification upgrades of the 6-Port Head

click here

......the 6 port head was first installed in BN4's from # 48863 ....

......all BN6's have the six port head


Period photo of the new style BN4 interior which lasted until to the introduction of the BJ8
Morris Green Engine Paint

The first batch of the six port cars had an unusual and unique feature in the Morris Green paint used on the engines and gearboxs. It appears that only some of the "first series" of six port BN4's produced at both Longbridge and Abingdon until the spring of 1958 had the Morris Green engines, for reasons unknown
In September 1958, production of BN4s resumed from car C.E.68959 and these cars featured a new style interior and other details  which were first introduced on the BN6   This interior is the same as that found on the 3000s and continued right through until the introduction of the BJ8. Amongst other things these cars have two windscreen washers, thin frame seat bases, a detachable hood frame and an armrest pad on top of the transmission tunnel, plus they have diferent quarter pannels and other minor trim differences, such as the door seals and furlex
BN4 - 6 Port Head (from car # 48863)
...all engines were painted at Coventry.......
 Roy Salvadori tested the new model and said:

..."the new 6-port induction system gives her an impressive increase in punch, particularly in top from 50 to 80 mph....the Austin-Healey always had plenty of dig but now its outstanding..."

Road and Track recorded a 0-60 mph time of 10.4 seconds
In late 1957 production moved from Longbridge to Abingdon with a short overlap period of production at both locations. At the same time a new head and separate six port cast aluminium inlet manifold was fitted to the BN4.

       Photo: William Taylor from: The Healey Book, Bill Emerson
4 types of BN4!

So in summary there are are actually four diffrent types of BN4, (if we include the cars with Morris Green engines.)

- the original `Longbridge` 2-port car

- the 6-port car with the  "Longbridge" interior and Morris Green engines

- the 6-port car with the `Longbridge interior and metallic green engines

- the 6-port car with the new style interior and features which were used up to and including the BJ7

The new carbs together with bigger valves and a higher compression ratio of 8.7:1 increased power to 117 bhp at 4,700 rpm. The new six port head had been developped  on the 1956 record breaker cars as well as the 1957 Sebring racers.

The 0 to 60 mph time was reduced to around
11 seconds and top speed increased to 112 mph. For those who think the 100-Six has insufficient performance it should be noted that these figures are virtually the same as the 3,000. 
Car # BN4L 49069 (J Soderling) is a six port car built at Longbridge November 1957 and has the Morris Green paint.

#BN4L 53878 (Ruud Gubbels)  built at December 1957  has Morris Green paint

#BN4L 54367 (Colin Watts)  built at early January 1958  has Morris Green paint

#BN4L 56053 (my car) built at January 1958  has Morris Green paint

Car #
BN4L 58563 (R. Lees) was built on March 6 1958  but has the standard metallic green engine paint. This would indicate that the Morris Green engine cars are rarer than thought and perhaps only lasted  until February 1958 before the "error" was corrected.

All engines were painted at the Morris plant in Coventry prior to dispatch to either Longbridge or Abingdon so it is logical that cars produced at both locations had the same colour engines. It is not known why it happened. It first appeared with the introduction of the six port engine, perhaps to differentiate it, or perhaps due to an error, it may even have been because they ran out of metallic green paint!! At some point between mid January and early March the error was corrected and the normal paint was re-introduced.
Morris Green engine paint -  Car 54367 Colin Watts

Breathing was through two semi-downdraft     1 3/4" SU HD6 carburetors.
Interiors and Fittings

When the six port model was first introduced the only changes from the earlier model were  the head and carburettor modifications as detailed above. The six-port car therefore began life with exactly the same "Longbridge"  features as the two-port car. These included the single windscreen washer, the same deep rim seat bases as the 100, saddle type arm rest and a sliding hood  frame mechanism that remained permantly attached to the body. The cars remained this way right up until BN6 production began in April 1956

Full details of the Longridge features can be seen seen at
 Longbridge features)

...some early 3000's still had 100-Six fitiings such as the horn push sign.....and conical reflectors........