Quoting Hugh & Therese <hugtrees@xxxxxxxx>: > problem really is. I maintain that problems on two cylinders only, numbers > four and six, are unlikely to be caused by the booster. Agreed. Loss of compression and potential vacuum leaks at the booster or other booster faults are independent and unrelated symptoms. However, a rough running engine could be due to a massive vacuum leak at the potentially faulty booster. It is also conceivable that a lean mixture in the number 6 and 7 cylinders due to the vacuum leak could have damaged the exhaust valves over time, causing the loss of compression in these two cylinders. However, if Bill has had indeed recently rebuilt the heads, that may not be very likely. Also, this usually happens when the car is driven hard, and I don't think Bill drives his 59 hard. > something else. If the engine cannot create sufficient vacuum in the tank, > fixing the booster unit will take time, money, effort and disruption and > achieve nothing. Good suggestion. It is easy to measure the vacuum. Just buy a vacuum gage (no more than $20) an install it on any vacuum line. Normal vacuum is usually over 15 inches, but anything over 12 will be sufficient to make the booster operate. D^2