An engine and a method of forming an engine are provided. The engine has a block that defines a cooling jacket extending continuously about an outer perimeter of first and second siamesed cylinders. The block defines a series of head bolt bores intersecting a deck face such that each cylinder is surrounded by four bores. The jacket has a first floor and a second floor. The second floor is offset above the first floor and extends along an intake side of the block between midpoints of the first and second cylinders, respectively. The second floor is configured to decouple a relationship between the cooling jacket and the series of bores for each cylinder and reduce fourth order bore distortion for each cylinder.

A compact power unit with a sufficient clearance between a stud bolt and a fixing shaft of a cam chain tensioner pivot mechanism for supporting a cam chain tensioner guide. The power unit including a crankshaft, a stud bolt configured to fix a crankcase and a cylinder body to each other, a cam chain, a cam chain tensioner mechanism including a cam chain tensioner guide, and a cam chain tensioner pivot mechanism including a pivot plate, a fixing shaft, and a swinging shaft, the fixing shaft and the swinging shaft are arranged so as to straddle the axis of the stud bolt as viewed in the axial direction of the crankshaft.

A cylinder head bolt inserted into a cylinder head is threadingly engaged with an engine casing comprised of a cylinder and a crankcase to tighten the cylinder head and the engine casing firmly together. Between a rotation operating part, which is provided in a head of the cylinder head bolt, and an upper surface of the cylinder head, a plain washer and a spring member placed thereabove are interposed. The spring member is capable of exerting an axially acting spring force. A first frictional resistance between the rotation operating part and the spring member is so chosen to be lower than a second frictional resistance between the spring member and the plain washer and a third frictional resistance between the plain washer and a bearing surface on the cylinder head.

An internal combustion engine (1) is designed so that the center axis P of a cylinder (4) is offset relative to a main journal part (2a) of a crankshaft (2). A bearing cap (17) is designed so that the side toward the cylinder center axis from a main bearing part (18) is secured to a bulkhead (7) by two fastening bolts (24a, 24c) while the side away from the cylinder center axis from the main bearing part is secured to the bulkhead by one fastening bolt (24b) and that the bearing cap securing force on the side toward the cylinder center axis from the main bearing part (18) is greater than the bearing cap securing force on the side away from the cylinder center axis.

A cylinder block includes a cylinder block body and a load path structure. The cylinder block body defines a first cylinder block upper bore. The load path structure includes a first support rib having a first support rib body interfacing with the first cylinder block upper bore. The load path structure is configured to transfer a load from the first cylinder block upper bore along a non-linear path within the cylinder block body away from the first cylinder block upper bore.

A compact power unit with a sufficient clearance between a stud bolt and a fixing shaft of a cam chain tensioner pivot mechanism for supporting a cam chain tensioner guide. The power unit including a crankshaft, a stud bolt configured to fix a crankcase and a cylinder body to each other, a cam chain, a cam chain tensioner mechanism including a cam chain tensioner guide, and a cam chain tensioner pivot mechanism including a pivot plate, a fixing shaft, and a swinging shaft, the fixing shaft and the swinging shaft are arranged so as to straddle the axis of the stud bolt as viewed in the axial direction of the crankshaft.

An internal combustion engine has a crankcase having a first crankcase portion fastened to a second crankcase portion along a first plane, a crankshaft, a cylinder block defining two cylinders, two pistons, and a cylinder head. A crankshaft support defines a crankshaft support aperture. A central portion of the crankshaft is received in the crankshaft support aperture. At least one fastener fastens the crankshaft support to the cylinder block. The at least one fastener is perpendicular to a crankshaft axis and is disposed in a second plane. The crankshaft axis is normal to the first plane. The second plane is one of coplanar with and parallel to the first plane.

A fastening structure for securing two disparate sections of an aluminum silicon alloy product. A precipitation hardenable austenitic stainless steel bolt engages each hole of a first and second aluminum silicon alloy product sections to fasten the sections together. The fastening structure is optimally utilized in a high temperature environment having thermal fluctuations. In such environments, the precipitation hardenable austenitic stainless steel bolt has less than 15% thermal relaxation after thermal fluctuations, and in some embodiments, less than 13% thermal relaxation after thermal fluctuations. The invention is of particular use for the fastening of an engine block crankcase utilized in a high temperature environment having thermal fluctuations where an engine block, a crankcase bedplate and a crankcase cover are formed from AA 362.0 alloy.

An internal combustion engine includes a first cylinder block, a first head, a first overhead structure, a second cylinder block, a second head, a second overhead structure, a first through-bolt aperture, and a first through-bolt. The first head is in contact with the first cylinder block. The first overhead structure is in contact with the first head opposite the first cylinder block. The second cylinder block is in contact with the first cylinder block opposite the first head. The second head is in contact with the second cylinder block opposite the first cylinder block. The second overhead structure is in contact with the second head opposite the second cylinder block. The first through-bolt aperture is defined through the first overhead structure, the first head, the first cylinder block, the second cylinder block, the second head, and the second overhead structure.

An internal combustion engine includes a first cylinder block, a first head, a first overhead structure, a second cylinder block, a second head, a second overhead structure, a first through-bolt aperture, and a first through-bolt. The first head is in contact with the first cylinder block. The first overhead structure is in contact with the first head opposite the first cylinder block. The second cylinder block is in contact with the first cylinder block opposite the first head. The second head is in contact with the second cylinder block opposite the first cylinder block. The second overhead structure is in contact with the second head opposite the second cylinder block. The first through-bolt aperture is defined through the first overhead structure, the first head, the first cylinder block, the second cylinder block, the second head, and the second overhead structure.