Editing User:Eric/sandbox/Progressive Refinements (section)

=== 1952 ===

{| class="wikitable"
|+
!Date Introduced
!Chassis No.
!Unit No.
!Modification
|-
| 18 Jan. 52
| 1-0320 113
20-020 804
|
| <u>Thermostat</u>
Now: simplified holder in a number of cases
|-
|21 Jan. 52
28 Jan. 52
|1-0320 804
20-021 054
|387 815
|<u>Gland nut</u>
Now: with felt seal to prevent loss of grease
|-
|21 Jan. 52
23 Jan. 52
|20-020 804
1-0320 113
|286 937
|<u>Thermostat</u>
Now: simplified holder standard
|-
|1 Feb. 52
4 Feb. 52
|1-0232 132
20-021 355
|390 307
|<u>Intake valve</u>
Now: induction-hardened

Formerly: surface-hardened
|-
|5 Feb. 52
|1-0323 802
20-021 398
|from 391 315
up to 359 379
|<u>Valve seat ring</u>
Now: made of lead-steel in a number of cases (3rd introduction)
|-
|7 Feb. 52
7 Feb. 52
|1-0 324 532
20-021 506
|392 231
|<u>Upper air duct</u>
Now: lateral support no longer fitted
|-
|21 Feb. 52
22 Feb. 52
|1-0 328 831
20-022 075
|397 264
|<u>Intake and exhaust valve cams</u>
Now: modified transition from surface end to radius, reduced noise
|-
|4 Mar. 52
6 Mar. 52
|1-0 338 059
10-023 584
|408 661
|<u>Exhaust pipe</u>
Now: connecting pipe between exhaust pipe and muffler no longer fitted
|-
|13 May 52
13 May 52
|1-0 352 446
20-026 314
|426 128
|<u>Pulley</u>
Now: a) pulley I, 45.0 mm

b) radial run-out: 1.0 mm

c) lateral run-out: 2.0 mm

Formerly: a) 58.0 mm

b) 0.5 mm

c) 0.1 mm 
|-
|29 May 52
29 May 52
|1-0 357 667
20-027 414
|443 003
|<u>Valve spring</u>
Now: one spring

Formerly: two springs
|-
|7 June 52
7 June 52
|1-0 360 478
20-027 952
|436 414
|<u>Oil dipstick</u>
Now: dipstick tube located higher
|-
|9 June 52
10 June 52
|1-0 360 851
20-028 063
|436 869
|<u>Fan wheel</u>
Now: balance center relocated
|-
|18 June 52
19 June 52
|1-0 364 368
20-028 709
|441 024
|<u>Crankshaft</u>
Now: thrust washer I =

0.30 ± 0.02 / II = 0.35 ± 0.03

Formerly: 1.1 – 1.2 – 1.3 – 0.9 – 0.9 mm 
|-
|20 June 52
21 June 52
|1-0 365 201
20-028 853
|418 210
418 102
|<u>Clutch operating lever</u>
Now: lever and adjusting nut with recess and chamfering
|-
|30 June 52
1 July 52
|1-0 368 508
10-029 529
|from 446 176
up to 451 092
|<u>V-belts</u>
Now: "Optiflex" material 13/8 x 50
|-
|20 Aug. 52
20 Aug. 52
|1-0 382 029
20-032 051
|462 001
|<u>Oil bath air cleaner</u>
Now: fitted in a number of cases
|-
|18 Sept. 52
18 Sept. 52
|1-0 391 619
20-033 964
|473 814
|<u>Clutch plate</u>
Now: "Textar" lining only from now on. Clutch plate 1.2 mm (formerly 1.5 mm)
|-
|23 Sept. 52
|20-034 214
|
|<u>Oil bath air cleaner</u>
Now: fitted in VW Ambulance (overhead arrangement)
|-
|26 Sept. 52
26 Sept. 52
|1-0 395 441
20-034 744
|478 493
|<u>Throttle ring support</u>
Now: guide projection for operating shaft in a number of cases

Formerly: recessed
|-
|26 Sept. 52
26 Sept. 52
|1-0 395 819
20-034 827
|
|<u>Flywheel</u>
Now: radial run-out limited to 0.2 mm
|-
|26 Sept. 52
26 Sept. 52
|1-0395 441
20-034 827
|478 493
|<u>Throttle ring</u>
Now: lever for operating rod with hole, screw head at level

Formerly: cotter pin. Screw head welded
|-
|Sept. 52
|
|
|<u>Intake manifold</u>
Now: with special jacket and jacket end (longer jacket casting). (Service part for Scandinavian countries)
|-
|1 Oct. 52
|1-0397 023
|481 713
|<u>V-belts</u>
Now: no longer included in tool kit

<u>Heating system</u>

Now: setting by rotary knob and spindle

<u>[[Carburetor / Progressive Refinements|Carburetor 28 PCI]]</u>

Now: carburetor 26 VFIS

<u>Fuel pipes</u>

Now: cross section 17 mm<sup>2</sup>

Formerly: 32 mm<sup>2</sup>

<u>Intake manifold</u>

Now: with preheating tube in joint aluminum-cast jacket
|-
|Oct. 52
|
|
|<u>Oil bath cleaner</u>
Now: two annular reinforcing grooves at the bottom
|-
|15 Oct. 52
|1-0402 111
20-036 112
|
|<u>V-belts</u>
Now: included in tool kit.
|-
|20 Oct. 52
|
|122-00 001
|<u>[[VW Industrial Engine]]</u>
Start of production
|-
|Nov. 52
|
|
|<u>Felt cone air cleaner</u>
Now: with flame guard screen
|-
|10 Nov. 52
|1-0 411 773
20-038 304
|498 719
|<u>Intake manifold support</u>
Now: beaded sheet metal strip

Formerly: pipe
|-
|10 Nov. 52
|from 20-039 360
up to 20-039 666
|from 503 889
up to 506 589
|<u>Starting dog</u>
Now: temporarily fitted in Type 2

Formerly: fitted in [[VW Industrial Engine]] only
|-
|26 Nov. 52
27 Nov. 52
|1-0 417 482
20-039 567
|505 970
|<u>Throttle ring support</u>
Now: guide projection for operating shaft (standard)

Formerly: recessed at collar
|-
|13 Dec. 52
15 Dec. 52
|1-0 423 415
20-040 811
|513 320
|<u>Intake valve</u>
Now: 4.9 dia. h 11

Formerly: 5.075 dia. h 11
|-
|31 Dec. 52
2 Jan. 53
|20-041 546
1-0 428 221
|517 651
|<u>Oil bath air cleaner</u>
Now: with strap
|}