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Specifications and the NCOP (National Code of Practice)

The NCOP has been adopted in WA. The following rules only apply in states that have adopted the NCOP.
 
In WA a vehicle modification application is used to list all the modifications you would like to make. If the application is approved you will be given a list of items that require engineering and references to the relevant regulations. If you are in doubt then list the modification.

Maximum Tares and NCOP engine capacities

    Naturally Aspirated Forced Induction
Model Tare kg cc ci cc  ci 
SL/R 5000 1281 6405 391 3843 235
SL/R 5000 A9X 1306 6530 398 3918 239
SS Hatch 1232 6160 376 3696 226
SS A9X Hatch 1242 6210 379 3726 227

Source: "60 Years of Holden" Terry Bebbington pg 338

The maximum engine capacity is based on the original tare of the model vehicle fitted the the largest engine available without optional accessories. WA currently uses 1204 kg for both hatch and sedan. However you should be able to get them to accept either the SS or A9X hatch tare for a hatch and the SL/R or A9X sedan tare for a sedan.

The engine must meet the pollution standards of the donor vehicle or the year of engine manufacture, you can not fit an older engine. For example a LS3 must run CAT's and the factory computer. In WA if you fit an aftermarket computer then you will be required to pass a five gas emission test which costs around $200.

See NCOP3_Section_LA_Engine_01jan2011_v3.pdf

Rims and Tyres

The maximum tyres size is limited by the largest optional tyre fitted by the manufacturer for that model (reference tyre).
 
The maximum tyre width is 1.3 times the reference tyre.
The tyre diameter must be in the range of -26mm to +15 mm of the reference tyre diameter.
 
The only requirement for rim width and diameter under the NCOP is that is must be within the tyre manufacturers recommended rim width range for the tyre fitted.

See page 21 of the NCOP11_Section_LS_Tyres_Suspension_Steering_V2_1Jan_2011%20v3.pdf.

For the LX Torana the reference tyres are the SS and A9X tyres.

Model Rim Offset in. Offset mm PCD Stud Tyre Circumference Feet Circumference Meters Dia mm
LX S & SL 13x5.5 JJ 1.25 31.75 5 X 4.25 7/16 UNF 175SR13      
LX RTS SL/R & SS 13x6.0 JJ 1.25 31.75 5 x 4.25 7/16 UNF CR70H13      
L34 & A9X 14x6.0 JJ 0.25 6.35 5 x 4.75 7/16 UNF DR70H14 6.3768 1.9436 619
 
Sources:
GMH L34 service bulletin
"60 Years of Holden" Terry Bebbington pg 338
Holden Torana Performance Handbook by Eric Blair 1993 p 115.
Rare Spares LX 6 cyl S SL SS SL/R tyre placard. Part No: 9941509
 
 
 
Notes:
The GMH L34 service bulletin lists the rolling circumference as 6.3768 feet  (1.9636 meters). The meters conversion is wrong (probably a typo). The meters conversion 1.9436 in the "Holden Torana Performance Handbook" is correct.

NCOP Tyre Widths and Diameters

    Standard NCOP
Tyre P-Metric Equivalent Std Width Std Dia Max Width Min Dia Max Dia
175SR13 175/80/13 175 610 228 584 625
BR78S13 175/80/13 175 610 228 584 625
BR78S13 185/70/13 185 589 240 566 604
CR70H13 195/70/13 195 603 254 577 618
DR70H14     619   593 638
DR70H14 195/70/14 195 629 254 603 644
DR70H14 200/70/14 200 636 260 610 651
DR70H14 205/70/14 205 643 267 617 658

Converting Alpha-Numeric to Modern tyre sizes

The metric equivalent of a DR70H14 is open to debate. It is most likely a 200/70/14 which would convert to either a 195/70/14 or a 205/70/14. According to the Car Bible Tire Size Conversion Chart it is a 200/70/14. According to the load rating conversion table below it is a 205/70/14. It appears that 195/70/14 is used for the NCOP and a 255 tyre is acceptable.
 
Using the rolling circumference of 1.9436 meters from the GMH L34 service bulletin the diameter of a DR70H14 is 619 mm.

The first letter of the Alpha-Numeric tyre size is the load rating and size relationship. The main problem is deciding which modern profile to use to for the Alpha-Numeric profile conversion. For example 78 could be converted to 80, 75 or 70. It appears to be common practice to round down to the most commonly available modern profile.

Load rating to modern 70 series
A = 175, B = 185, C = 195, D = 205, E = 215 etc.
 
Load rating to modern 80 series
A = 165, B = 175, C = 185, D = 195, E = 205 etc.

Rims-n-Tires.com - Wheel / Tire Size Calculator

The Wheel and Tyre Bible Page 1 of 2

Rim Width Measurement

The trick to rim measurements is that the rim width is measured from the inboard tyre bead seat to the outboard tyre bead seat. Backspace is measured from the inboard flange to the hub. There is typically 0.5" of flange beyond the tyre bead seat. If you measure an 8" wide rim from flange to flange it will measure 9.0". If you measure from the inboard tyre bead seat to the outboard tyre bead seat it will measure 8.0".

Inboard Flange  = Typically 0.5"
Outboard Flange = Typically 0.5"
Overall Width  = Inboard Flange + Rim width + Outboard Flange
Rim Centreline = Overall Width / 2
Offset = Back Space - Rim Centreline
Back Space = Rim Centreline + Offset
Front Space = Rim Centreline - Offset
 
When comparing different width rims you should look at the offset. If the offset stays the same then the centre of the rim will be in the same position. If the offset stays the same then the backspace will increase or decrease by half the increase in rim width.
 
7" rim with 4" backspace has 4 - 4  = 0 Offset
8" rim with 4.5" backspace has 4.5 - 4.5 = 0 Offset

Rims-n-Tires.com - Wheel / Tire Size Calculator

Tire Size Conversion Chart

The Wheel and Tyre Bible Page 1 of 2


 
The middle of a 8" rim is (0.5 + 8.0 + 0.5) / 2 = 4.5". With a 5.5" backspace then the offset is 5.5 - 4.5 = +1.0"
The middle of a 7" rim is (0.5 + 7.0 + 0.5) / 2 = 4.0". With a 4.5" backspace then the offset is 4.5 - 4.0 = +0.5"

Track

Wheel track is measured from the centre of the tyres. Wheel track will vary on the front suspension depending on ride height as the control arms swing in an arc. To maintain track all you have to do is maintain the standard offset regardless of the rim width.

The track can not be reduced and can only be increased by a maximum of 25 mm. If you are fitting flares then you should be able to use the A9X track as your base track.

Front and Rear BUF calculations based on rim offset and track figures

    Imperial Measurements - inches Converted Metric Measurements mm
Model Source Rim Offset Track Front Track Rear Front BUF Diff BUF  Rim Offset  Track Front  Track Rear  Front BUF  Diff BUF
LX RTS SL/R & SS LX Owners Manual 1.25 55.30 54.40 57.80 56.90 31.75 1,405 1,382 1,468 1,445
L34 Holden Torana Performance Handbook pg. 64-65 0.25 57.89 56.82 58.39 57.32 6.35 1,470 1,443 1,483 1,456
L34 60 Years of Holden pg. 337 0.25 57.90 56.82 58.40 57.32 6.35 1,471 1,443 1,483 1,456
A9X 60 Years of Holden pg. 337 0.25 57.90 56.82 58.40 57.32 6.35 1,471 1,443 1,483 1,456
A9X Just Holden's - A9X edition pg. 23 0.25 58.50 57.10 59.00 57.60 6.35 1,486 1,450 1,499 1,463
 
Notes:
I measured my LX Torana diff as 1446 mm from BUF to BUF. This agrees with the Diff BUF calculation for the LX RTS SL/R & SS.
The "Holden Torana Performance Handbook"  lists the rim offset as -0.25" for the A9X and +0.25" for the L34, this appears to be a typo as the GMH L34 service bulletin lists the rim offset as +0.25".
The L34 track calculations indicate that the L34 Diff BUF is wider than LX Diff BUF which is unexpected.
The "Just Holdens" track figures for the A9X are different to the L34 track figures. I would expect the front track figures to be the same for the L34 and A9X as they have the same front suspension and rim offsets.  "60 years of Holden" list the same track for L34 and A9X. The A9X diff could had a different BUF measurement to the L34 diff.
 
Sources:
LX Torana owners manual
Holden Torana Performance Handbook by Eric Blair
60 Years of Holden by Terry Bebbington
Just Holdens Toranas collectors series A9X

Fuel Tank

The fuel tank must be fitted with an unleaded fuel restrictor and labelled unleaded fuel only. I fitted the filler neck from a VN Commodore. You can buy press in unleaded  fuel restrictors. If you have a aftermarket tank then it must comply with the departure angle rule to be engineered. Drop tanks for example Brown Davis that do not comply with the departure angle rule have been know pass over the pits but they will not pass the engineering checklist.

See page 5 and item 1.7 on page 12 of  NCOP9_Section_LM_Fuel_Systems_01Jan2011_v2.pdf

Diff Housing

The LH parts and LX parts manuals list the following housings.

Housing Assy - 2.78:1, 3.08:1 A.R.            6 cyl Eng                              2819067
Housing Assy - 2.78:1, 3.08:1 A.R.            4.2 Litre Eng                        2819067
Housing Assy - 3.36:1, 3.55:1 A.R.            6 cyl Eng                              2819068
Housing Assy - 3.36:1, 3.55:1, 3.90 A.R.   4 cyl Eng                              2819068
Housing Assy - 2.78:1, 3.08:1 A.R.            5 Litre Eng exc L34 Eng.      2825743
Housing Assy                                             L34 Eng                                9935109
Housing Assy                                             A9X option                           92002517

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