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Up until R16 engine number 40000, all the threads in the
engine were US thread. Starting with 40001, they switched to metric except
for the cylinder head bolts and rod cap bolts. All the U20's were metric sizes, except
for the head bolts and rod cap bolts. Here are the sizes used.
| Usage |
R16 From E/#40001,
All U20 |
R16 Through E/#40000 |
Torque
(where specified) |
| Crank pulley bolt |
M16 x 1.5 |
5/8 - 18 UNF |
145 ft/lb |
| Head bolt |
7/16 - 14 UNC |
|
65 ft/lb |
| Main bearing cap |
M12 x 1.75 |
1/2 - 13 UNC |
65 ft/lb (U20) |
| Connecting rod cap |
7/16 - 20 UNF |
7/16 - 20 UNF |
65 ft/lb (U20) |
| Oil pan |
M6 x 1.0 |
1/4 - 20 UNC (bolt)
5/16 - 18 UNC (stud) |
3.5 ft/lb (U20) |
| R16 Rocker cover |
M8 x 1.25 |
5/16 - 18 UNC (nut)
1/4 - 20 UNC |
|
| R16 Valve rocker bracket |
M10 x 1.5 |
7/16 - 20 UNF |
|
| R16 Camshaft gear |
M10 x 1.5 |
3/8 - 16 UNC |
32-36 ft/lb |
| U20 Cam tower to head |
M8 x 1.25 (large)
M6 x 1.0 (small) |
n/a |
|
| U20 Cam tower bearing caps |
M8 x 1.25 (large)
M6 x 1.0 (small) |
n/a |
13 ft/lb (M8)
5 ft/lb (M6) |
| U20 Jackshaft gear |
M10 x 1.5 |
n/a |
32-36 ft/lb |
| U20 Camshaft gear |
M8 x 1.25 |
n/a |
13 ft/lb |
| Timing chain tensioners |
M6 x 1.0 |
1/4 - 20 UNC |
|
| Manifold |
M8 x 1.25 |
5/16 - 24 UNF
5/16 - 18 UNC (stud) |
|
| Carburetor |
M8 x 1.25 |
5/16 - 24 UNF (nut)
5/16 - 18 UNC |
|
| Air cleaner |
M8 x 1.25 |
5/16 - 18 UNC |
|
| Air cleaner support |
M8 x 1.25 |
5/16 - 18 UNC |
|
| Water pump bolt |
M8 x 1.25 |
5/16 - 18 UNC |
|
| Water pump stud |
M10 x 1.25 |
3/8 - 24 UNF |
|
| Fan blade |
M6 x 1.0 |
1/4 - 28 UNF |
|
| Front cover |
M8 x 1.25 |
1/4 - 20 UNC |
|
| Water outlet |
M8 x 1.25 |
5/16 - 18 UNC |
|
| Distributor mounting |
M6 x 1.0 |
1/4 - 20 UNC |
|
| Fuel pump |
M8 x 1.25 |
5/16 - 24 UNF |
|
| Oil filter mount |
M10 x 1.25 |
3/8 - 24 UNF |
|
| Oil pump to block |
M8 x 1.25 |
5/16 - 18 UNC |
5.8-7.2 ft.lb |
| Oil pump cover |
M6 x 1.0 |
1/4 - 20 UNC |
|
| Oil pump strainer |
M6 x 1.0 |
1/4 - 20 UNC |
|
| Generator bracket |
M8 x 1.25 |
5/16 - 24 UNF |
|
| Flywheel to crankshaft |
M10 x 1.25 |
3/8 - 16 UNC |
58 ft/lb (U20) |
| Clutch cover to flywheel |
M8 x 1.25 |
5/16 - 24 UNF |
|
| Bellhousing |
M10 x 1.5 |
3/8 - 24 UNF |
|
| Starter to bellhousing |
M10 x 1.5 |
3/8 - 24 UNF |
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