0DELETED_monkeyman1140Best Answer 10 years ago ReplyUpvoteCommercial model rocket engines for bottom and middle stages are designed to "burn through" and send hot gases upwards when they burn up the last of their fuel. Taping the engines together sometimes can keep the 2nd stage from releasing unless very little tape is used. If you want long burning engines for a rocket car, you can buy larger engines. A D-12 engine burns for only something like 4 seconds, as the number refers to the impulse power rather than the burn time. I believe there are E and F engines with much longer burns. Model engines don't really get very hot, which is why model rockets are almost always made of paper. The spent engine casing surface will get hot enough to possibly burn your skin, but not hot enough to ignite anything.