They used to sell a gadget to do that over here not all that long ago - probably still got one lyin' about somewhere. Tony might well invent the first internal combustion steam engine eh? They did have converted steam engines in the early oil well country of the USA. Special heads with igniters replaced the head of the steam engine, and I guess you had to blank off the steam port on the front end of the engine. Natural gas from the well was used as fuel as it still is on some wells in isolated areas. Some of these hybrids still exist in the collections of early type gas engine fanatics. Interesting but not as good as a made for the job gas engine. >Actually, Tony, you COULD replace one of the spark plugs in your automobile >with a check valve and use that cylinder as a compressor. Didn't you haveto disable the intake valve on the cylinder being used as a compressor inorder to prevent doing what Charles said and have an explosive mixture? Red Neck Tennesseean 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.