Do you need certain size headers for a 2.2
 

if i were to change from heat exchangers to headers could i use any old headers as long as there for a 911 or do i have to use headers for a 2.2 engine.

the idea is not to have to big of pipes, or you'll loose back pressure and low end torque

however, Bruce Anderson's book has some data which suggest the HE's are not the source of backpressure , but points towards the muffler as the bottleneck

also depends on what 2.2 you're talking about and what your goal for this engine is...

Pelican recommends 1-5/8 Inch Internal Diameter for engines under 3L
and 1-5/4 Inch Internal Diameter for engines over 3L

why do you want to go to headers? to get more power?
don't excpect much of it... the net result is minimal

Your stock is ~1 1/2" = ~38mm OD which is ~1 3/8" = ~35mm ID. Plenty good for even a 2.2 S.

You certainly want to keep the ID > 1 1/2", w/ a primary length of ~29"

even though SSI are heat exchangers, the header core(1 3/8" = ~35mm)) is superb for the smaller engines >3 liters, especially for a mostly street motor

i dont really want to go to headers to be honest i dont even own a porsche i was just asking to learn. thanks for all the help. the more i learn the more i realize what i dont know.

Thanks
Evan