Related Clues:

• Gas guzzlers
• 35-Down's quartet
• They might backfire
• They go to blazes
• Firehouse vehicles
• Ramjets, e.g.
• Some roarers
• Car parts
• Power sources
• Firefighters
• Driving forces
• The ends of 18- and 60-Across and 3- and 31-Down are types of them
• They're under hoods
• Fire trucks
• Things to rev