Re: 1947 Super Clipper idle problem

Posted by Dave Kenney On 2012/1/7 15:05:12

For one thing the Mityvac is a vacuum pump not a vacuum gauge which is what Dave was referring to. The instument you have is handy for checking the vacuum advance and bleeding brakes however. When hooked up to the intake manifold via the small plug on the intake the vacuum gauge will measure the amount of vacuum the engine is creating and it should be around 18-22" (unless you live at high altitude) if all is normal. With the gauge installed and engine running the idle screws can be adjusted to achieve maximum vacuum for that which should be where they are set although I like to turn them out just a tad more to give a slightly richer mixture. The gauge will also give you information on valve condition, late timing and a number of other useful information. It is a must have instrument.
There are any number of websites which will explain how to use and interpret a vacuum gauge but here is a good one.autospeed.com/cms/title_Using-a-Vacuum-G ... ine-Diagnostics/A_2393/article.html

Check the points gap also as that will affect idle and timing as well.