The Toyota Y engine is a design that's a combination of the Toyota T engine

Toyota T engine

The Toyota T series is a family of inline-4 automobile engines manufactured by Toyota beginning in 1970 and ending in 1985. It started as a pushrod overhead valve design and later performance oriented twin cam variants were added to the lineup...

, and the Toyota R engine

Toyota R engine

The Toyota R family was a series of straight-4 gasoline engines. Designed for longitudinal use in such vehicles as the Celica and Hilux and in production from 1953 through 1995, use faded out as many of Toyota's mainstream models moved to front-wheel drive...

, in a way that's similar to how the Toyota F engine

Toyota F engine

The Toyota F series engine was a series of OHV inline-6 cylinder engines produced by Toyota between 1955-1992. They are known for their high amount of torque at low RPM, massive cast iron blocks and heads and also their high reliability. The F Engine had one of the longest production runs of any...

 is a design of the Toyota Type B engine, and the Chevrolet inline-6.

The valve arrangement from the Toyota K engine

Toyota K engine

The Toyota K series was a straight-4 engine produced from 1966 through 1988. It was a 2-valve pushrod engine design, a rarity for the company....

 is interchangeable with this engine.

Translated from Japanese Wiki :ja:%E3%83%88%E3%83%A8%E3%82%BF%E3%83%BBY%E5%9E%8B%E3%82%A8%E3%83%B3%E3%82%B8%E3%83%B3

1Y-J

• OHV 8 valve
• Aerodynamic volume displacement: 1.626L
• Inside diameter × distance: 86.0×70.0 (mm)

Applications:

• (First)light/write ace(YM20)
• Town ace(YR10)

2Y, 2Y-U

• OHV 8 valve
• Aerodynamic volume displacement: 1.812L
• Inside diameter × distance: 86.0×78.0 (mm)
• Compression ratio: 8.8
• Reference output: 58kw (79ps) /5,000rpm 140Nm (14.3kgm) /3,200rpm

Applications:

• 5th generation mark II van(YX76V)
• 3rd generation highace van (YH50V/60V)
• Townace van (YR25V)
• Liteace wagon (YM20/30G)

2Y-P

• OHV 8 valve (LPG)
• Aerodynamic volume displacement: 1.812L
• Inside diameter × distance: 86.0×78.0 (mm)
• Specifications: 63kw (85ps) 5,000rpm 142Nm (14.5kg-m) 3,000rpm (Gross value)
• 51kw (70ps) 4,600rpm 132Nm (13.5kg-m) 2,200rpm (net value)
• LPG

Applications:

• Corona(YT140)
• Mark II (YX70)

3Y, 3Y-U

• OHV 8 valve
• Aerodynamic volume displacement: 1.998L
• Inside diameter × distance: 86.0×86.0 (mm)
• Compression ratio: 8.8
• Reference output: 65kw (88ps) /4,800rpm 155Nm (15.8kgm) /3,400rpm

Applications:

• 3rd generation high ace wagon (YH51G/61G/71G)
• Hilux
• Dyna/ToyoAce

3Y-E

• OHV 8 valve
• Aerodynamic volume displacement: 1.998L
• Inside diameter × distance: 86.0×86.0 (mm)
• Compression ratio: 8.8
• Reference output: (97ps) /4,800rpm 160Nm (16.3kgm) /3,800rpm

Applications:

• 5th generation mark II van (YX78V)
• Hilux (YN60)
• Daihatsu Rocky (Australia)

3Y-EU

• OHV 8 valve
• Aerodynamic volume displacement: 1.998L
• Inside diameter × distance: 86.0×86.0 (mm)
• Specifications: 85kw (115ps) 5,000rpm 179Nm (18.3kg-m) 3,600rpn (Gross value)

71kw (97ps) 4,800rpm 160Nm (16.3kg-m) 3,800rpm (net value)

Applications:

• Hilux Surf
  Toyota Hilux Surf
  The Toyota Hilux Surf is an off-road vehicle manufactured by Toyota, sold mainly in Japan, with large numbers exported as used vehicles to Pakistan, Afghanistan, United Kingdom, Ireland, New Zealand, and Australia...
  
  /4Runner
  Toyota 4Runner
  The Toyota 4Runner is a mid-size SUV manufactured by Toyota and sold throughout the world from 1984 to the present. In Japan it was known as the Toyota Hilux Surf...
  
  (61G)
• TownAce wagon (YR21G)

3Y-P

• OHV 8 valve (LPG)
• Aerodynamic volume displacement: 1.998L
• Inside diameter × distance: 86.0×86.0 (mm)
• Output: 79ps (58kw) /4,600rpm 15.0kgm (147Nm) /3,000rpm 2000rpm

Applications:

• Crown(YS130)
• Mark II(YX80)

3Y-PU

• OHV 8 valve (LPG)
• Aerodynamic volume displacement: 1.985L
• Inside diameter × distance: 86.0×86.0 (mm)
• Specifications: 66kw (90ps) 5,000rpm 157Nm (16.0kg-m) 3,000rpm (Gross value)

58kw (79ps) 4,600rpm 147Nm (15.0kg-m) 2,000rpm (net value)

Applications:

• Crown (YS120)

3Y-PE

• OHV 8 valve
• Aerodynamic volume displacement: 1.998L
• Inside diameter × distance: 86.0×86.0 (mm)
• Compression ratio: 10.5
• Output: 60kw (82ps) 4,600rpm 157Nm (16.0kg-m) 2,400rpm (1989 July? 1995 November)
• 58kw (79ps) /4,400rpm 160Nm (16.3kgm) /2,400rpm (1995 December? )

Applications:

• Crown(YS130 1989 July -)
• Comfort(YXS11)
• Crown comfort(YXS10)
• Crown sedan(YXS10)
• Mark II (YX70)

4Y-E

• OHV 8 valve
• Aerodynamic volume displacement: 2.237L
• Inside diameter × distance: 91.0×86.0 (mm)

Applications:

• Toyota Van(town ace overseas specification)(Tarago in Australia)
• 3rd generation Hiace (overseas specification)
• Toyota Industries forklifts