Hot tank first to get grease, carbon, and oil paint etc off. Next you can try muriatic acid - chemically known as hydrochloric acid (HCL), fast acting, depending on how rusty, it will take probably only a few hours. Inspect your parts once or twice an hour, flush with water each time and you may want to wire brush to get chunks off. Soak in acid until the rust is gone and flush with clean water. Immediately immerse them in caustic water (drano or lye dissolved in water) to neutralize the acid and to prevent flash rust, and then flush with water again. Dry them with compressed air, heat them with a propane torch to get all water out, and coat them immediately with the paint of your choice. A light coat of oil WD40 etc inside will keep them from rusting again until engine runs. Save the acid it stays strong and effective for a long time. I use 5 gallon buckets to store it. A large plastic flat pan is suitable to soak parts. BE CAREFUL. HCL and drano/lye are very destructive to concrete and you. USE heavy rubber gloves and eye protection. Never add water to HCL or other strong acid, instead add the acid to water. Spattering can occur from the heat of solution if water is added to acid, acid added to water allows the heat to dissipate immediately.