Hello, I have a 1989 740 GL 5speed with 152,000 miles. I have noticed that when I stop at a stop sign that there is a noise, similar to a depressureization, added to a slight drop in rpm's. The drop is slight, by about 250rpm's or so. It also happens when I place my foot on the gas pedal. I have the engine run to about 1,500, then it drops to about 1,250, or about 1,000. My brother thinks it is the water pump. I am not sure. Also I have noticed a quite noticible rattle/buzzing whenever I shift. it happens right before I push in the clutch, at about 3,000rpm's and then again after I let it out again. I believe it to be the timing belt, but I am inexperienced with volvo's. Another noise I have noticed, is a semi-loud chirping/whine when I start the car. This even happens when the car is warmed up.

A final question, would a chevy 305v8 fit? the car currently has a 2.3 litre four-cyl. Would that help to add performance and value? I have noticed that the gas mileage is not much worse. I get about 18 in the city, and 24ish on the highway.

Thanks for your time, and any opinions!! It is greatly appreciated.