An engine supplied with an FAA 8130-3 form should be OK for a privately used G-reg. I think this is fine for any SE plane since a SE plane is highly unlikely to be used for any AOC work.
There is a widely floated suggestion that one should ask the U.S. supplier to write "for export to the UK" in Box 13 of the 8130-3 form. This is believed to lubricate any CAA inspector looking at it later, and is easy to get because it means basically nothing - it is stating only the bleeding obvious!! OTOH CAP562 (see below) suggests that the CAA-FAA treaty makes such a note superfluous.
However, for another $200 or so, you can get the engine accompanied by an 8130-4 which is an Export CofA (a form signed by an FAA DAR) and that is good for anything on G - as far as I've been able to find out. This is true for Class A parts (engines and props). You must get this form
with the engine; one cannot get it generated later.
One reference is CAA
AN14. Another is
CAP562 (page 174 mostly I think). Read it as you wish
Everybody else seems to
Interestingly, AN14 dispenses with the often quoted statement that an EASA-1 form is required for any G-reg for any aircraft part. Any traceability document is in fact OK. It is engines and props that are different (potentially). AOC aircraft (hardly applicable to SE) are also said to be more strict but I have not found a clear statement on this yet. Running an AOC plane on mandatory EASA-1 forms must be a maintenance nightmare, not to mention the gravy train for the part vendors who type these forms up from fresh air.
Karl
More than one person has imported used aircraft and engines to the UK only to find the CAA refuse a CofA.
Can you give more details of exactly what happened? An FAA Export CofA is normally done in these cases.