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18R engine

Most data copied from Toyota's "18R Engine Repair Manual", 1983.

The 18R engine is an overhead cam, overhead valve engine with 4 inline cylinders.
The block is cast iron and the cylnder head is usually cast iron.
Twincam versions (18R-G, 18R-GU, 18R-GEU) use twin overhead cams in an alloy head.
All twincam versions of the 18R can use unleaded fuel because all alloy heads have hardened valve seats.
The single cam versions without hardened valve seats (18R, 18R-B) should use leaded fuel.
The single cam versions with hardened valve seats (18R-U, 18R-C) can use unleaded fuel.
Gaskets can be shared between all versions (twincam can use gasket goop around timing cover).
Inlet and exhaust manifolds are different for single and twin cam versions.
Many parts are interchangeable with other R series engines.
The twincam head is not compatible with the 20R or 22R block.
Most cars with any R series engine can accept the 18R.
All cars with any 18R can accept the twincam versions.
The twincam has a unique exhaust.
All other 18R variants can share heads and exhausts.
Most versions use the same data except for timing.

The 18R-G, 18R-GR and 18R-GU use twin Mikuni Solex sidedraft PPH40's with the same bolt pattern as Weber DCOE's.
The 18R-GEU EFI system can be bolted to the other 18R twincam heads.
The 18R-GEU can be converted to carbs by using the manifold and carbs from the other 18R twincams.

Early 18R twincam heads had small valves with large cams.
Over time the valves grew larger and the cams grew milder.
All 18R twincam heads can be interchanged.
All 18R twincam cams can be interchanged.

The twincam and single cam blocks are identical except for the oil dipstick hole.
Both blocks have bosses for the dip stick on both sides.
Single cam has a hole drilled in the boss on the exhaust side for the dip stick.
Twincam has a hole drilled in the boss on the dizzy side for the dip stick.

The twincam and single cam cranks are identical.
The twincam can use the single cam oil filter mount after it has been shortened to except a Z386 oil filter.

The twin carb 18R-B is identical to the single carb model (18R, 18R-C) except for the manifold and the twin carbs.
The 18R-B carbs are identical to the 18R and 18R-C carbs except for the jetting.

The twincam and single cam distributors have different bodies but the internals can be interchanged.
You can upgrade to electronic ignition by using the distributor internals from any R or T series engine with EI
(eg 18R-GU, 18R-GEU, 18R-EU, 2T-GEU, 3T-EU, 13T-EU).
You also need the corresponding ignitor module.
Note: early model EI has an external ignitor bolted to the coil and later model EI has the ignitor inside the distributor.
Both types can be used on any R or T series engine.

The 8R is almost identical to the 18R except for the bore and stroke.
The 10-R is identical to the 8R-G.
An 8R head on an 18R block raises the compression for more power.

It has been reported that 12R oil pan fits the 18R, making it easier to replace a 12R with an 18R.
Maybe somebody can try a 12R head on an 18R block.
The 12R directly replaced the almost identical 4R and 9R.
The 9R was a 4R with a twincam head.
It is not known how much the 9R twincam shares with the 18R-G twincam.

I suspect the 16R is also the same as the 18R apart from bore and stroke.
The 16R shares the same head gasket as the 18R-C, so a 16R head can probably
be used on an 18R block to raise compression.
It may also be possible to put an 18R-G twincam head onto an 1800cc 16R block.

Engine	Difference from 18R
18R-C	uses PCV and charcoal cannister for low emmisions
18R-E	EFI
18R-U	uses TTC-C for low emmisions
18R-G	twin overhead camshafts, twin sidedraft carbs, 9.7 CR
18R-GR	twin overhead camshafts, twin sidedraft carbs, low compression for regular fuel
18R-GU	twin overhead camshafts, twin sidedraft carbs and TTC-C
18R-GEU	twin overhead camshafts, EFI and TTC-C
8R, 10R	Different bore and stroke but head is interchangeable with 18R

Common settings
Bore x Stroke	88.5x80mm
Displacement	1968cc
Inlet valve clearance - hot	0.20mm (0.008")
Exhaust valve clearance - hot	0.36mm (0.014")
Timing 18R	10° BTDC at 600rpm
Timing 18R-C auto	5° BTDC at 650rpm
Timing 18R-C manual	5° BTDC at 750rpm
Timing 18R-E	10° BTDC at 850rpm
Timing 18R-G(R) auto	5° BTDC at 1000rpm
Timing 16R manual	7° BTDC at 700rpm
Timing 16R auto	7° BTDC at 750rpm
Timing 16R-B	10° BTDC at 800rpm
Firing order	1-3-4-2
Idle speed	750 ± 50 rpm
Fast idle speed	2600 ± 200 rpm
Manifold vacuum at idle	420mm Hg (16.5" Hg)
Compression - standard	11.5kg/cm² (163.1psi)
Compression - minimum	9.0kg/cm² (127.8psi)
Compression - max difference between cylinders	1.0kg/cm² (14.2psi)
Spark plug 18R	Denso W20EP, NGK BP6ES
Spark plug 18R-G(R)	Denso W20EX, NGK BP6EZ
Spark plug gap 18R	0.7mm-0.8mm (-0.03")
Spark plug gap 18R-G(R)	0.9mm-1.0mm
Max spark plug lead resistance	25kOhm
Distributor heel gap	0.45mm
Distributor damping spring gap	0.1-0.4mm (0.004"-0.168")
Dwell angle	50°-54°
Dwell variation	3°
Ignition timing	7° BTDC/750±50rpm

Torque settings - 18R-G
Cylinder head	7.2-8.8kgm (52.1-63.7ftlb)
Camshaft bearing cap	1.6-2.2kgm (12-15ftlb)
Camshaft timing gear	7.0-8.0kgm (50.6-57.9ftlb)
Camshaft drive gear	6.0-7.0kgm (43.4-50.6ftlb)
Intake manifold	1.0-1.6kgm (7.2-11.6ftlb)
Exhaust manifold	3.5-4.5kgm (25.3-32.6ftlb)
Crankshaft bearing cap	10.0-11.0kgm (72.3-79.6ftlb)
Connecting rod cap	6.4-7.0kgm (46.3-50.6ftlb)
Oil pan	1.0-1.6kgm (8-12ftlb)
Crankshaft pulley	8.2-8.8kgm (59.3-63.7ftlb)

Last updated 27 Dec 2007