As you are aware, Porsche made constant upgrades to all of their cars through the years, often in mid-production year.

There was a question about when the square tooth style of cam belt changed to the rounded tooth. I thought it was mid-1983 or MY 1984. I took a look at the 1983 Service Information manual (different than Workshop Manuals) and found that it was listed as a change for model year 1984. I thought I'd provide a few of the other major improvements for the 928 MY 83

- 4.7 liter engine, all US/Canada models were "S" model.
- rounded tooth cam belt (carry over from 944)* Note 1
- improved hydraulic dampening of the cam belt
- Improved Air Conditioning air disribution
- Improved windshield wipers
- Steering wheel and instument pod available in different colors
- hydraulic motor mounts (previous were solid with external dampener), new style mounts can be retrofitted to older models.
- starter motor NOT mounted in bell housing, uses a metal frame directly attached to the engine block (said to make the starter quieter), clutch slave cylinder was changed.
- oil pump drive gear changed from sinthered alloy to light alloy.
- intake system of oil pump: doesn’t have threaded in filter screen and plastic insert with rubber funnel. This was done to prevent intake of foreign particles.
- Cylinder head gaskets were changed June 15, 1982 (prior to MY ’83 change over). The new gasket has 4 edge reinforcements and uninterrupted silicone bead.
- change of head stud types (a special Technical Information Bulletin was published to announce the introduction date and engine numbers for the new studs)
- fuel feed and return lines shape and radius in the area of head were changed to provide greater distance to the spark plug cap of cylinder
number 3.
- Fuel line return to gas tank is cooled by air conditioning to reduce fuel heating (problem in warmer climates when car isn’t moving or is driven at low speeds).
- radiator inlet pipe modified to prevent some hot water from leaving the radiator in an uncooled condition.
- USA & Canada: 4 speed Automatic Transmission introduced.
- USA & Canada: higher gear ratios for better fuel economy.
- purging of carbon canister is regulated by load condition
- electrically heated O2 sensor to guarantee functionality even at idle speed and after long driving with throttle shut-off (a heated O2 sensor can be retrofitted to older models, route the heating wire to terminal number 15 on the fuel pump relay.
- Up-shift indicator lamp (US Manual trans. only)

Note 1: My 1983 928 was upgraded to the new style cam belt in 1996 by the PO. My build date was Nov. 1982 (early 1983 model). So, even if your car is a 1983 model, it may NOT have the newer style belt. Be sure to check when changing, DON'T just go by what part is listed for the year.

 

My 83 Euro S, delivered 10Jan83, had a round tooth belt when I did it last year, and at 41k miles indicated, I dont think it had been done before. I think this change came early in the 83 MY, but I may be wrong?
jp

 

I believe there was an '83.5 change in the brakes
also; not size but in mounting/ positioning that requires some different parts.