text: Engine details The SRT-4 used the same basic engine block as the naturally aspirated 2003+ 2.4L, and was different from the years previous used in the naturally aspirated Chrysler 2.4L mid-size cars such as the PT Cruiser and four-door Stratus. The SRT4 engine had many improvements, including: stronger crank case webbing, a thicker deck with 11 mm head bolts (vs 10 mm), an oil drain back for the turbo, a cast aluminum structural oil pan, a higher capacity oil pump, a crankshaft of higher hardness steel, improved machining of bearing journals, oil squirters (to cool underside of pistons), eutectic aluminum alloy pistons made specially by Mahle, and forged connecting rods with cracked caps and 9 mm bolts. The cylinder head was also different for turbo engines, from naturally aspirated. The turbo version (PT Cruiser GT Turbo and SRT-4) included: larger diameter valves and seats, exhaust valves made of Inconel, improved cooling and larger oil drain back passages, different camshafts. The PT Cruiser Turbo engine package differs from the SRT-4 because the intake manifold, turbocharger plumbing and intercooler are different. The SRT-4 intercooler was a front-mounted cast aluminum 8-row unit produced by Valeo, unique in its efficiency and computer designed end tanks for air flow.