do you know where to check the timing? Do you know about the BB in the flywheel, and the pointer in the bellhousing? I only ask because you were wondering if you should check from under the front bumper. That shouldn't even be a question. The octane selector can be anywhere as long as it is tight. Unless the gas in your area tends to vary widely in octane levels ( I have never used it in 30 years) The screw you found loose is what is used to set the timing. Some people say to set the timing with a vacuum gauge, I have always used the prescribed "ball and pointer" method, but last week I decided to give the vacuum method a try, I found absolutely no difference in performance.
