The M54 engine came in a few different displacements from 2 liter through 3 liter. The 2 liter had a bore of 80mm. The rest of the 2.5 liter through the 3 liter engines had an 84mm bore.
- 2.2 liter - bore 80mm - stroke 72.0 mm - compression 10.8:1 - hp 168
- 2.5 liter - bore 84mm - stroke 75.0 mm - compression 10.5:1 - hp 189
- 3.0 liter - bore 84mm - stroke 86.9mm - compression 10.2:1 - hp 228
The ZHP 235 hp version of the 3.0 has the same stoke and bore. The differnce is the camshafts.
M54b25 // int: 228º(9.0mm) // // exh: 244º(9.0mm)
M54b30 // int: 240º(9.7mm) // // exh: 244º(9.0mm)
M54b30ZHP // int: 248º(9.7mm) // // exh: 248º(9.7mm)
At 340,000 miles my 325i started feeling a little tired and the transmission failed on drive from Atlanta to Montgomery AL. Not being one to quit, I sent the transmission off to Eriksson Industries for a reman. This was going to take a while so I decided that this was a good time to upgrade the stock 2.5 to a 3.0 ZHP.
I purchased a 3.0 crankshaft and rods as well as a set of used ZHP cams and set about doing a rebuild. I had also purchased a set to oversize pistons anticipating that this engine surely needed do be trimmed after 340,000 miles. To my surprise all 6 cylinders were perfectly round and straight. All that was needed in this case was a cleanup hone.
New rings, bearings, timing chain kit and a new head and the ZHP was nearly ready. A new set of high flow cats, a Vanos rebuild and a tune injection to the ECU and we were back in the game.
ZHP Camshafts
3.0 Stock Connecting Rods
3.0 Forged Crankshaft