If photon 1 and 2 are position entangled and they go in different directions, would making a measurement on photon 1 effect photon 2? If photon 1 is detected can photon 2 still create interference?
I'm unsure what position-entanglement of photons would mean, but with entangled particles in general, performing a measurement on one particle does not affect the other, contrary to what some science popularizers would have you believe. An entangled system is just a system where the measurements performed on the two particles will be correlated in a way that is impossible under classical assumptions. If it were possible to actually affect the other particle by making a measurement, then you could communicate instantaneously over an arbitrarily large distance, which would violate special relativity.
If you have a pair of position entangled photons ,you measure one of them ,the other will collapse .For example ,entangled photons emitted at orgin , and photon 1 was detected at x,then photon2 you will detect it at -x .
"If photon 1 is detected can photon 2 still create interference?" I do not know what you want to express. Actually, when one of photons is measured ,the other will be a real single photon and a single photon can interfere with itself.
Hope it can help you.