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Tomei MAIN BOLTS EJ20#/EJ25#

Tomei MAIN BOLTS EJ20#/EJ25#

SKU: 193113
Regular price £614.13
Regular price Sale price £614.13
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The EJ engine cylinder block and crankshaft design is not really suited for high power use so the main bolts are important to maintain strength in the block. The stress that the block endures is susceptible to deformation of the crank main journals which can increase friction and ultimately bearing failure. The TOMEI main bolts are designed to suit high power applications to prevent the block from warping and to ensure rigidity.


※Main Bolts
※BP/BL Compatible
193113 ・M10 Bolt (Washer Seals) x6
・M10 Bolt Long x2
・M8 Bolt Long x1
・ M10 Washer x4
・M10 Bolt Short x2
・M8 Bolt Short x6
・M8 Washers x7
* Dummy head cylinder boring is highly recommended to get the best result for the bolt installation.


MATERIAL * Chromemoly 8740
SIZE M10 P1.25

Since the EJ cylinder block lies flat and splits into 2 halves the crankshafts movement phenomenon puts extra burden on the studs with the 180° phase reciprocating motion of the pistons. When the gap opens this prevents the Main Bearings from maintaining the correct clearance which will lead to an engine blow. The TOMEI studs will ensure that the blocks are held together even during extreme conditions.

Bolts and screws in general will stretch when placed under stressful conditions. The stock bolts will tend not to return perfectly to its original shape once stretched due to the manufacturing methods used for the original purpose of the bolt design. Tuned engines will go through many procedures which require the bolts to be reused during every step. When having a dummy head installed and getting a bore and hone, when checking for bearing clearances and so on. So when the bolts are removed and torque up repeatedly bolt stretch management will then become difficult to manage the and retain the strict clearances required. The TOMEI Stud bolts are the best choice for high performance precision engines which require the fixed elastic range of the bolt set for repeated use and to maintain performance. The TOMEI Bolts will keep your engine together when needed most.

Rotation processing is the method of Rotating Die and Work Hardening the raw core of the bolt is placed on the cradle between the two rotating die with pressure applied from both sides. The metallic crystals within the bolts are then deformed at a microscopic scale, and then interacted with one another to make up a strengthened bolt that carries increased yield strength. The chromoly steel of the Tomei strengthened bolt is first heat treated and rolled on the rotating die, increasing impact resistance, surface strength, and longevity. These standards add up for the highest quality product available.

An engine cannot be properly built without the use of the angle torque method when tightening certain bolts. It is necessary to utilize a special angle gauge when tightening strengthened studs and connecting rod bolts. Applying torque to the bolts without this specialized tool can lead to immediate or eventual catastrophic failure of the engine assembly.
Lack of bolting force Excessive bolting force
Head bolt ・Leaking gas, water, oil caused by lack of the sealing pressure
・The further fall of bolting force, loosening, and engine breakage.
・ Leaking gas, water, and oil from excessive bolting or failure of sealing pressure.
・Breakage of the cylinder from distortion.
・Poor piston clearance caused by cylinder distortion.
Crank bearing cap bolt
Conrod bearing cap bolt
・Worn out of the engine by bad bearing assembly.
・Noise by too much clearance of bearing.
・The further fall of bolting force, loosening, and engine breakage.
・Worn out of the engine by bad bearing assembly.
・Worn out of the engine by poor clearance of the bearing.

Engine components that require precision accuracy when tightening its bolts cannot be trusted with basic torque figures. This is due to 80~90% of the friction is lost on the surface of the thread and the seat when tightened, with the correct figure being at 10~20% of the torque applied. The surface of the thread and the seat depends on the roughness of each surface and the lubrication state, so that no matter how accurate the torque specs are specified it cannot be trusted.

【Change of Axis force due to the difference of friction of the washer】 
Please use an Angle Guage as well when torquing up these TOMEI Reinforced Bolts.
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