rpm and at 2,800 rpm. In 1985, the engine was significantly reworked, output was up to at 4,800 rpm and at 3,600 rpm. Many parts from the newer 22R/R-E are not compatible with those from the older pre-1985 engine. Non-compatible parts include the cylinder head, block, pistons and many of the associated parts such as the timing chain and cover, and water and oil pumps (although the oil pump internals are the same). These changes also affected the 22R, therefore one can consider the 85–95 22R-E as a fuel injected version of the 85–90 22R with only minor differences, if any. Toyota swapped the dual-row timing chain used in older engines for a single-row chain with plastic guides in 1983. The new system reduced drag on the engine but introduced a new maintenance problem. After about of operation, the chain may stretch to the point that the hydraulic-operated chain tensioner cannot take up any more slack. The timing chain then impacts the plastic driver's side chain guide, breaking it within a short period of time and creating a noticeable chattering sound in the front of the engine, especially when cold. If the engine continues to be operated without the guide restraint, the chain will vibrate excessively on the driver's side and stretch rapidly. The result is any of several failure modes. First, the loose chain will reduce ignition timing accuracy, which usually results in noticeably rough running. Second, it may jump a tooth on the drive sprocket or break entirely, which almost always results in major damage to an interference engine. Third, the stretched chain can slap against the side of the timing cover and wear through the metal into the coolant passage behind the water pump, resulting in major damage to both the oil and cooling systems (sometimes mis-diagnosed as a head gasket failure). The damaged aluminum timing cover is difficult to repair effectively and is typically replaced after such an event. Aftermarket timing-chain kits for the 22R/R-E typically include steel-backed guides that do not readily break even after the initial chain stretching has occurred, permitting the chain to run beyond the point without further incident. However, some Toyota mechanics will recommend the plastic guides as they will break when the timing chain is stretched; When the guides break a noticeable chatter is heard from the timing chain slapping on the cover, warning the operator of a worn timing