BMW M4 G83 ST — S58B30 Engine Rebuild

Along­side the bent con­nect­ing rod in cylin­der 6, the crank­shaft was also found to be dis­tort­ed due to exces­sive heat gen­er­at­ed by the fail­ure of the con­nect­ing rod bear­ings. This was not an excep­tion, as two oth­er con­nect­ing rods had also begun to show signs of bend­ing. The bear­ing fail­ure most like­ly occurred after the con­nect­ing rod bent under load, caus­ing it to bind and gen­er­ate sig­nif­i­cant heat.

The rotat­ing assem­bly was rebuilt with a new crank­shaft, a set of CP forged pis­tons, and CP-Car­ril­lo H‑beam con­nect­ing rods to ensure improved strength, dura­bil­i­ty, and bal­anced per­for­mance under high-load con­di­tions.

The cylin­der head was resur­faced and rebuilt with upgrad­ed com­po­nents, includ­ing Fer­rea valves, a Kelford camshaft set, and a match­ing valve spring kit. The stock head bolts and crank­shaft main bolts were replaced with high-strength ARP studs to improve clamp­ing reli­a­bil­i­ty. In addi­tion, the new­ly installed crank­shaft and CP-Car­ril­lo H‑beam con­nect­ing rods were fit­ted with a fresh 5150 Autosport main and con­rod bear­ing set, com­plet­ing the upgrad­ed rotat­ing assem­bly pack­age.

The engine was reassem­bled using the new, high-strength com­po­nents, and was ful­ly pre­pared for instal­la­tion back into the vehi­cle. The entire build process was com­plet­ed in our con­trolled clean­room envi­ron­ment to ensure max­i­mum pre­ci­sion and pre­vent con­t­a­m­i­na­tion of crit­i­cal engine com­po­nents.