This is NOT a good idea for the reason you mention and several others. Depending on the type of car, and how you do it, you may also damage the electronic ignition, oxygen sensor and catalytic converter. If you need a cheap and dirty small air compressor, go to a DIY auto store and get a $10 USD one that plugs into the cigarette lighter on the car. It is meant to pump air to 75-80 psi or more and probably costs less in time and money than buying or making a check valve and possibly damaging the car using it. Good luck, Jeff Dayman Waterloo Ontario Canada ----- Original Message ----- From: "Charles & Dorothy Brumbelow" <cbrumbelow@xxxxxxxxxxx> To: <modeleng@xxxxxxxxxxxxx> Sent: Sunday, September 11, 2005 4:47 PM Subject: [modeleng] Re: Steam engine RPM? > Actually, Tony, you COULD replace one of the spark plugs in your automobile > with a check valve and use that cylinder as a compressor. That was a tip in > one of the early (prewar?) DIY magazines here in the states. Might have > been fine to fill up a tire after repairing a flat, but it sounds a lot like > a potential bomb if you filled up a metal tank with the mixture of gasoline > and air under pressure. Charles > MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.