Manifold Heat Exchanger Fits John Deere 60 620 630 70 720 730 A4644ROne New Aftermarket Replacement Manifold Heat Exchanger for John Deere Tractors This manifold heat exchanger mounts between the intake and exhaust manifold sections on classic John Deere two cylinder gas tractors, transferring heat from the exhaust side to warm incoming intake air and fuel for improved cold weather starting and combustion efficiency. It is a direct drop in replacement for the original John Deere (JD) A4644R heat exchanger used across