https://www.epa.gov/sites/production/files/documents/engswitch_0.pdfEPA received many questions regarding the application of this law to a situation where one engine is
removed from a vehicle and another engine is installed in its place. EPA's policy regarding "engine
switching" is covered under the provisions of Mobile Source Enforcement Memorandum No. lA
(Attachment 1). This policy states that EPA will not consider any modification to a "certified
configuration" to be a violation of federal law if there is a reasonable basis for knowing that emissions
are not adversely affected. In many cases, proper emission testing according to the Federal Test
Procedure would be necessary to make this determination.
A "certified configuration" is an engine or engine chassis design which has been "certified" (approved)
by EPA prior to the production of vehicles with that design. Generally, the manufacturer submits an
application for certification of the designs of each engine or vehicle it proposes to manufacture prior to
production. The applicaion includest design requirements for all emission related parts, engine
calibrations, and other design parameters for each different type of engine (in heavy-duty vehicles), or
engine chassis combination (in light-duty vehicles). EPA then "certifies" each acceptable design for use,
in vehicles of the upcoming model year.For light-duty vehicles, installation of a light-duty eng~ne into a different light-duty vehicle by any
person would be considered tampering unless the resulting vehicle is identical (with regard to all
emission related parts, engine design parameters, and engine calibrations) to a certified configuration of
the same or newer model year as the vehicle chassis, or if there is a reasonable basis for knowing that
emissions are not adversely affected as described in Memo 1A. The appropriate source for technical
information regarding the certified configuration of a vehicle of a particular model year is the vehicle
manufacturer.
For heavy-duty vehicles, the resulting vehicle must contain a heavy-duty engine which is identical to a
certified configura- tion of a heavy-duty engine of the same model year or newer as the year of the
installed engine. Under no circumstances, however, may a heavy-duty engine ever be installed in a
light-duty vehicle.(The is important, your emissions can match the same year or NEWER) my understanding is if you have a "heavy duty" ecm from a tbi heavy duty motor then you should be ok. I would contact your state's Attorney General's office to see what they say. if they really want to argue that your ecm isnt for a heavy duty engine go get one from a junk yard from a 87 with GVWR of 8501+.
The most common engine replacement involves replacing a gasoline engine in a light-duty vehicle with
another gasoline engine. Another type of engine switching which commonly occurs, however, involves
diesel powered vehicles where the diesel engine is removed and replaced with a gasoline engine.
Applying the above policy, such a replacement is legal only if the resulting engine-chassis configuration
is equivalent to a certified configuration of the same model year or newer as the chassis. If the vehicle
chassis in question has been certified with gasoline, as well as diesel engines(as is common), such a
conversion could be done legally.
B. State Laws
Many states also have statutes or regulations prohibiting tampering in general. Most of these laws
specifically prohibit tampering by individuals. A few specifically prohibit engine switching, using
provisions similar to those stated in EPA's policy. To determine the state law in any given state, the
state's Attorney General's office should be contacted. In addition, many states have state or local
antitampering inspection programs which require a periodic inspection of vehicles in that area, to
determine the integrity of emission control systems. Many programs have established policies for
vehicles which have been engine switched. While EPA does not require these programs to fail engine
switched vehicles which are not in compliance with federal policy, the Agency does strongly
recommend that these programs set their requirements so as to be consistent with the federal law. State
or local programs which pass illegally engine switched vehicles may mislead federally regulated parties
into believing that engine switching is allowed by federal law.