I don't know anything about Seafoam so I can't help you there--but I would say this--before introducing anything other than motor oil to the crankcase I'd like to know it's needed. If you do the cam check/valve clearance first you'll have first hand evidence if there is a buildup of sludge. A car that looks as nice as yours probably (hopefully) has also been maintained well too. Regular oil changes and a good balance of highway miles will keep the interior of a motor clean and any special treatment shouldn't be necessary. I'll give you two instances where a "treatment" was necessary. Years ago I worked with my dad at his used car lot. We sometimes bought cars at auction that came from the electric or telephone companies--AMC Hornets and Ford Falcons--and often their 6 cyl. motor's valve train was so noisy you couldn't hear yourself think and the Fords especially, would smoke out the tailpipe. For these cars we added a quart or two of kerosene--ran them hot--drained the mixture and repeated. After draining them the second time we'd change the filter and add motor oil. Most of the time that was enough to get the lifters working and the rings freed up. In the worst cases we removed the valve cover to find so much sludge you couldn't even see the rocker arm shaft and rockers--hidden in a mass of solid sludge. The other type of instance involved carbon deposits on the pistons. For those I'd run them at brisk rpm and introduce water through a vacuum inlet. When I had a self designed water injection system on my '68 144 B18 and later removed the worked B20 head to transfer it to the '69 B20 I still have--the pistons in the B18 were perfectly clean. AS FOR THE CENTRIFIGAL ADVANCE--there are two systems in the distributor to modify the timing. The vacuum retard (or advance) moves the breaker plate with a rod either opposite the direction of rotor rotation (advance) or with the rotor direction (retard). The other system is the centrifigal advance--located below the breaker plate and connected to the top of the distributor shaft (which is independant of the lower half of the shaft) using two spring loaded pivoting weights. As the rpm rises the weights force the upper section (with the rotor) to advance ahead of the lower part of the shaft. If you grab the rotor with your fingers you should be able to rotate it in the direction of rotation (counterclockwise on the B18/20/30) and it should snap back when released. TOOLS--with a 1/2 inch, 9/16, 11/16 and a 3/4 inch wrench you can pretty much disassemble most the car. Basic wrench and socket sets will see you through most jobs. -- sorry for all the verbiage -- I guess I like writing---Dave