Comp XE275HL Idle Vacuum

20-227-4 - Xtreme Hi-lift Hydraulic Flat Tappet Camshafts
Comp XE275HL
275/[email protected]/110+4/61overlap and 231/[email protected], w lifts of .525/.525
Compares to my Hughes at;
276/[email protected]/110+4/61overlap and 230/[email protected], w lifts of .549/.571
Docile as heck with aluminum heads and 10.9Scr. Plenty of vacuum at 750 to run the F-body/mid 70s Dart single diaphragm booster. It would not work properly with the dual diaphragm 69/70 type unit. Mine idles down to 550rpm at 5* advance for parading at 4mph with 3.55s and a manual trans. If the vacuum bleeds down while parading, a blip of the throttle while declutched and it's charged up again.
IDK the vacuum exactly,lol; maybe 10ish@750@14* idle-timing. But IDK at 550 and 5*,lol.

With an automatic ,by the time you have backed out of the driveway, and are moving forward in first gear, it should be fine. If not just blip the throttle a time or two.
When gently slowing down from speed, just before coming to a stop,with disc-brakes, is when a deficiency might show up; just downshift into first, and the rise in rpm will suck it up in a couple of heartbeats.
Or do what I did;
Put big fat tires on the back with drum brakes and eliminate the P-valve. Then let the drums haul you down the last car length or two. Problem solved/ drive normal.. With this set-up I was able to run the mighty 292/292/108 Mopar cam at 11.3Scr, also at 14* idle timing, on that same booster.