Paper work needed for upgrading an engine

I asked a question about an engine upgraded to higher horsepower (assumed it was an engine swap). Evidently the engine in question on a plane for sale is the original 582 the plane had however the cylinders and related hardware were replaced with 670 parts by Rotax Rick to make the 670 power plant. Essentially it is a big bore 582 with the original serial number for the plane. My question is what have those that have the "zipper kits" on the 9 series, or bored out engines done as far as paper work? The guy selling the plane is telling me his A&P looked over the paperwork and said most don't even upgrade the paperwork since it is the same engine same serial number, but if you did it would just be a 5 hr phase 1 fly off and file the paperwork. Opinions?
Mark

An engine change is considered a major change. That requires the phase 1 flight test and notifying the FAA. Being that this is the same serial #, it sounds like the same engine to me with some different parts. I don't think you need to do the major change thing. YMMV. JImChuk

What if it's the original engine, just rebuilt. Is there a 5 hours fly off and more paperwork to do?

I would doubt an engine rebuild would fall under a major change requiring a return to phase I condition.

Check your operating limitations, anyway.

An engine rebuild does not constitute a major change. I suspect the OPs engine modifications constitute a major change by the intent of the rule. A significant change in power will affect how the craft flies. I also suspect it may meet the letter of the law given the same serial number. I would call the FSDO with a plan to go back into phase 1 for a couple of hours.

I have dealt with major changes and it was no big deal in our FSDO(Atlanta). We changed a prop and removed slats on a Zenith 750. Called the FSDO with our plan for 5 hours back into phase 1 with the same geographic area as original. They said OK. 5 hours of testing; climb, descent, stall, etc and log book entry and we were back in business.

I'm going to have to change the prop as well. The old wood prop had a TBO of five years and had been setting for ten. So I'm thinking of an IVO prop.
Sounds like I still will have the five hours?

I am pretty sure a prop change is a "major change" requiring some phase I time. I do not think there is a standard amount of time. Just have a reasonable plan before you call the FSDO. I think reasonable is; enough time to test stalls at different loading. Rate of climb. Rate of descent. Of course with a ground adjustable prop you will want to test several different pitch settings. I had what I felt was a reasonable plan in mind when I called the FSDO. The guy there made some notes I guess and got our N number and that was it. A new weight and balance may be in order as well.

The 670 cylinders will not fit on a 582 Block. A 670 crank will not fit a 582 block either. So it is a different engine.