SZ,
No, there is none in our Vol I for a cross-bleed start.
"757/767-200/-300 Operations Manual
Supplementary Procedures - Engines, APU
SP.7.3
Engine Crossbleed Start
The APU must be shut down or the APU bleed air switch must be OFF.
Check that the area behind the airplane is clear.
Engine Bleed Air switch (operating engine) ......................................ON
Advance thrust on operating engine to approximately 70% N2 and
accomplish normal Engine Start procedure."
Perhaps you are thinking of the huffer cart start?
"Engine Ground Pneumatic Start
Check duct pressure 30 psi or greater.
Start engine using normal Engine Start procedure.
Two ground pneumatic air sources are required."
This time of year 70% N2 does in fact yield about 30psi.