Quote Originally Posted by tortron View Post
Carbon build up causing pre-ignition
High vac reading can be overly advanced timing. If it's all carboned up itl ignite before it sparks.

Did it run on a bit when turning the key off?
I have never had an issue with Pre-ignition. Just low vaccum driving down the road.

Yesterday in a very strong head wind I had to turn off the OD just to keep at 65 MPH on the highway. It would in OD but I would have to almost floor it to do it.

I really think the engine is extremely warn out. Off the highway in the headwind I could get 8 in of vacuum at 50 mph.

To me that says this engine is WAY down on power as it needs a ton of throttle to make any power.