He might also be referring to getting the header to fit over the exhaust studs. I had to heat and adjust the header pipes to get the right spacing for the flanges. Yes, it was a real PITA.Installing those headers is a real PTA. The easiest way is to remove the engine, put the headers in the chassis, and then reinstall the engine. Some people remove the cylinder head and then slip the headers in place. You may be able to lift the engine enough to slip 2&3 in place without completely removing the engine, however. They're nice headers but a very tight fit. Have you talked to Centerline about this? They may have some better ideas.
I routinely used to plan on heating new headers and bolting them to a spare head. Once cooled they would fit right on with no trouble. The later iterations of Alfa aftermarket headers have all seemed to be a lot better in this department. The last 101 Veloce headers from Centerline I saw (not on my car) actually fit quite well. That said, it's always a good idea to test fit a new set of headers before trying to fit them on your car. The Alfaholics stainless GTA style headers that went on my Super were/are a perfect fit.I had to heat and adjust the header pipes to get the right spacing for the flanges. Yes, it was a real PITA.
I wonder how many other vendors have that kind of quality control program?With the conversion headers, we test fit each and every set on a spare head when we receive them into inventory. I usually make the *least* experienced member of our staff test fit the headers. They have to fit with nothing more than bare hands and a small screwdriver or prybar to get them started over the studs. Some sets slip right on, others take a little pressure/prying but if they won't fit they go back to the manufacturer for correction.
Motor mounts un-bolted from the chassis , engine hoist on top , jack on the bottom . Can I tell you how much to tip it ? no , trail and error . As was stated....much easier to lay them in before the engine is installed .