[ajay99]

karl, i will check the points raised by you and reply later .
in the meantime
changes for the year 1966

1966 (1 Aug 65 to 31 July 66)
Chassis: 116,000,001 - 116,1021,300*
Engine: D 0,000,001 - D 0,095,049 1200 34bhp (DIN)
*********** E 0,000,001 - E 0,006,000 1300 37bhp (DIN)
*********** F 0,000,001 - F 0,940,716 1300 40bhp (DIN)*

Note the new type of engine numbers. The prefix denotes the engine type. 1300 engine introduced.
"1300" badge on engine lid. 30PICT/1 carburettor. Cam bearing shells added to engine. Emergency blinker switch. Ventilated wheel slots and flatter hub caps. Bigger rear view mirror. Headlight dimmer moved to turn signal lever. Centre dashboard defroster outlet. Horn ring - semi circle. Ball joint front suspension replaces king pins. Improved torsion bars 10 leaves in each tube, and distance between tubes increased from 120mm to 150mm. Tapered roller wheel bearings replace ball bearings. Anti-burst door locks. Safety lock for front seat backrests. 1300 with 30PICT/1 carburettor has longer accelerator pump connecting rod.*

changes for years 1967 to 1970 already posted earlier in this thread.will continue in next post

years 1971-1972
1971 (1 Aug 70 to 31 July 71)
Chassis: 111,2000,001 - 111,3200,000*
Engine: D 0,675,000 - D 0,835,006*
*********** AC 0,000,001 - AC 0,003,239 40bhp(DIN)1300*
*********** AB 0,000,001 - AB 0,141,591 44bhp(DIN)1300*
AF 0,000,001 - AF 0,000,444 46bhp(DIN)1600*
AD 0,000,001 - AD 0,360,022 50bhpDIN (65bhpSAE 1600)*
AE 0,000,001 - AE 0,558,000 47bhpDIN 60bhpSAE 1600(USA)

Dual port 1600 engine. Three part induction manifold. Better quality alloy used in crankcase. Solex 34PICT/3 carburettor. Combination vacuum/centrifugal distributor (double vacuum and retarded ignition on US models AE engines). Activated charcoal filter to catch fuel fumes. New larger oil cooler mounted doghouse' style venting to atmosphere gives better cooling to No 3 cylinder. Bigger capacity cooling fan. New clutch throw-out assembly and ball release bearing. Headlights go off when ignition off. Crescent vents behind rear window for improved cabin ventilation. Bigger front brakes- 248mm dia x 45mm (drum brake models). Towing eye added to front torsion bars on 1200 and 1300 models from Nov 70.

First year for Super Beetle: Re-designed front end with McPherson strut suspension, louvered front apron (Standard beetle still in production too).*
Crescent vents behind rear quarter windows in US
All models get "3 point" front seat mounts.

1972 (1 Aug 71 to 31 July 72)
Chassis: 112,2000,001- 112,3200,000 (or might be 112,2961,362)
Engine: D 0,835,007 - D 1,000,000*
*********** AC 0,003,240 - AC 0,006,700*
*********** AB 0,350,001 - AB 0,699,001*
*********** AF 0,000,445 - AF 0,000,801*
*********** AE 0,558,001 - AE 0,917,263*
AH 0,000,001 - AH 0,005,900 47 bhp(DIN)1600(USA)*
AD 0,360,023 - AD 0,598,001*

Engine lid gets 4 sets of air slots. Smog control models get extra plumbing (both studs and supers). Windscreen wiper switch mounted on steering column stalk. New steering column. New distributor with vacuum retard (5 degrees ATDC) at idle. EGR (exhaust gas recirculation) added for California cars. New muffler. Modified 3rd and 4th synchro rings to reduce noise. "Baja bug" introduced. Karman Ghia gets disc front brakes in US (already from 67 in other countries). Wheels change from 5.6x15 to 6.0x15 in late 72. Larger rear window. Collapsible hub steering wheel. Hinged parcel shelf over rear luggage area. Restyled speedo. Clutch operating arm lengthened in Sept 71.

to be continued in next post

year 1973
1973 (1 Aug 72 to 31 July 73)
Chassis: 113,200,001 - 113,3200,000
*** VW1303 133,300,001- 133,3200,000*
Engine: D 1,000,001 - D 1,115,873*
*********** AC 0,006,701 - AC 0,008,195*
*********** AB 0,699,002 - AB 0,990,000*
*********** AF 0,000,802 - AF 0,036,768*
*********** AE 0,917,264 - AE 1,000,000 (to 1 Oct 72)*
*********** AK 0,000,001 - AK 0,239,364 (from 1 Oct 72)*
*********** AH 0,005,901 - AH 0,114,418*
*********** AD 0,598,002 - AD 0,990,000*

Reduced horsepower in US models (60 to 58 SAE). 600 watt (50 amp) alternator replaces generator in mid year. Improved intake pre-heating for faster cold weather warm-up. Engine case near No3/flywheel are reinforced to prevent cracking. Softer transmission mounting. Softer clutch. Porsche style pressure plate. Oil drain plug removed from oil strainer cover plate. New fuel pump (with cut-off valve) to clear alternator. Paper air filter. New lifetime lubricated' front and rear wheel bearings. Redesigned fresh air system. New interior light assembly. Stronger bumpers. Large round tail lights added.. Sports Bug' option. New front seats with multiple adjustment.

Supers get: Larger curved windscreen and smaller front lid to luggage compartment. New dash. Front turn signals larger.

1974 (1 Aug 73 to 31 July 74)
Chassis: 114,200,001 - 114,2999,000*
*** VW1303 134,200,001 - 134,2999,000*
Engine: D 1,115,874 - D 1,284,228*
*********** AR 000,001 - AR 121,271 44bhp(DIN)1300*
*********** AS 000,001 - AS 171,566 50bhp(DIN)1600*

Self restoring energy absorbing bumpers. Quieter muffler. New cylinder head alloy for better heat dissipation. "Softer" steering wheel to improve safety. Smaller front headrests give better rear vision. Computer sensor pressed into top of block to give TDC. Computer sensor for ignition voltage. Seat belt ignition interlock. Seat belt and brake warning light combined. Super beetle and convertible have slight negative king pin offset. Super beetle has square glove box knob. Warning light for hand brake. Ghia has thicker front disc pads. Last year of Ghia in the US. Internal regulator to alternator in late 74, distributor gets vacuum and centrifugal advance.* Wider track for front (new strut arrangement) and rear wheels, steering wheel collapses even more than in previous models