Joined: Jan 2010
Posts: 9,830
Likes: 1,807
From: Northern California
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Heat will expand the aluminum cup far more than the steel race, allowing the race to fall into place with minimal force.
The cup should be hot enough to boil water, not much hotter than to smoke oil.
You were quite lucky! You are only supposed to use the flat end of the bushings (or no bushings with the Park press) to press in this vintage of Campag headset!
I've seen the inner race cracked by using the smaller end of the Park bushings, even happened to me, ONCE!