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Engine Swaps Made Easier
Hobbyists frequently ask us about the rules governing engine switching in project vehicles. First of all, those engaged in engine switching activities are bound by specific state laws that may vary from state to state. Having said that, there are some general guidelines one may consider. This article will cover the rules for switching the engine in production-type vehicles (but not specially constructed vehicles, street rods, kit cars and the like). The basic rule of engine switching (as opposed to installing a "replacement" engine) is that the change must do no harm. This means that the engine being installed must theoretically be at least as "clean" as the one taken out. Several requirements may define "clean" for the purposes of engine switching:
Model Year: The engine to be installed must be the same age or newer than the one being replaced. Crate engines can be used if they are configured to resemble an engine that was certified by the U.S. Environmental Protection Agency and/or the California Air Resources Board. This essentially means that the required emissions parts must be present on the engine.
Certification Level: The engine to be installed must come from a vehicle certified to meet the same or more stringent emissions standards than the one replaced.
Vehicle Class: An engine from a vehicle class such as a motor home, medium-duty truck or marine application must not be used since these engines were certified to different types of emissions standards, using different tests.
System/Equipment: When swapping in a newer engine from a later-model vehicle, all of the relevant emissions control equipment must be transferred as well. This includes the carbon canister, the catalytic converter(s) and even parts of the on-board diagnostic (OBD) system. Some states have exceptions to this requirement, but the general rule is that as much of the donor vehicle's emissions system as possible should be transferred. The vehicle will likely run more efficiently with a full transfer of the system and shouldn't cause any undue heartache.
Of course, engine switching can be much more complex than described here, but these are good general rules to follow and should keep engine switchers out of trouble in most cases.
The U.S. EPA and many states have enforceable policies and guidelines on how to perform legal engine changes. For further information, please consult the EPA and California Bureau of Automotive Repair at: