How can I tell if I have a 170 or 225 s6 in my 64 Dart?
Look at the water pump bypass hose under the thermostat housing area at the front of the head. If it is a 170, the hose will be very short. If it is a 225, the hose will be longer, mayne 3.5-4" as opposed to 2.5-3". Of course, if it has the long hose, it could also be a 198. Although the 198 would not have come in the car, it is certainly old enough to have had one swapped in. To be for sho and for certain, get the casting number off the driver's side of the block.