The Series IV was introduced in November 1964. Identified by its Chassis (VIN) number B94 prefix. The 7 digit number became 8 in September 1964. 12,406 units were produced by September 1965. The SIV continued to use the 1592cc engine along with the single twin choke Solex carburettor. Still available in both GT and ST variations, the SIV has the most visually drastic changes. Most notably the removal of the fins. Now a more squared off rear end sporting re-designed rear lights.
The front indicator lights were also changed to a two bulb unit with an amber turn signal and a clear parking light. Other exterior changes include: New bumper over riders, hinged petrol tank cap, single bar grille with Rootes medallion, Series IV badge motif located under the Alpine scripts and on the right hand side of the boot lid. Midway through Series IV production, there would be a change to the Series IV serial number and an extra digit would be added. These are known as IVA's and begin with chassis number B94100000. The IVA also marked a change in transmission from a non-synchronized gear box to a fully synchronized unit. The Borg Warner type 35 automatic transmission was also available on both the SIV and SIV a platforms. They can be identified by a B.W. stamped after the Chassis number. It's not known how many of these Automatics were produced.