Air carrier Technician reported that after accomplishing work on both engines; they had difficulty closing the pylon access panels due to it being damaged during the engine run.

Narrative

I was assigned Aircraft X with Person A and Person B. Our job assignment was to remove and install the L/H engine fuel transmitter and the R/H engine transmitter. We had one of the fuel transmitters in stock; but the other transmitter was being AOG'd on a flight that landed at XB:30. We locked out the slats and T/R's (Thrust Reversers) with me pulling the associated circuit breakers and Person A deactivating the T/R valve. Locking out the T/R requires an access door on each pylon to be opened and the T/R valve pinned in the open position. We then removed and installed the transmitter we had on hand on the L/H engine but didn't get the other transmitter for the R/H engine until approximately XC:30 (one hour after it was on the aircraft the part was AOG'd on). The aircraft was linked on a flight at XG:00 which gave us 3 and a half hours before departure to perform the task. As soon as we got the transmitter at XC:30 we started installing it on the R/H engine. At approximately XE:00 we had finished installing the transmitter. With both transmitters installed; we needed to conduct three tests. One being a part power engine run where N1is 50 percent. We accomplished the part power engine run and then shut down the engines. We then reopened the engines to verify the new components we had replaced weren't leaking. Leak check was good. We closed the engines and were in the process of reactivating the T/R's. I went to the E&E compartment where the circuit breakers were located and closed them and Person A and Person B started to reactivate the T/R valve in the left and right pylons. As I came over to them after closing the circuit breakers Person A and Person B approached me saying they were having trouble closing the access doors. The access doors had been left opened; not to my knowledge; and the engine run had caused the lower hinge on both doors to warp. This prevented the doors from closing which made the aircraft non-airworthy.Cause: Before we were to run the engines I was on the right side of the L/H engine when I saw Person A with the lift truck on the left side of the L/H engine. To save time so the aircraft can make its departure time I told Person A not to reactivate the T/R valve in the pylon until we were done with the leak check. I was under the assumption that the pylon access door was closed with the streamer showing out of the access door; and I had never physically saw the access doors open during any time of the operation. I got confused with the 777 aircraft and 787 aircraft. The 787 you can close the T/R access door with the streamer hanging out of the door to verify the T/R valve is pinned. On the 777 aircraft you cannot close the access door with T/R valve pinned. Person A agreed not to reactivate the T/R valve. We ran the engines and the engine run had caused the lower hinge on both access doors to warp preventing the doors from closing.Suggestions: I've deactivated the T/R's numerous times on the four different fleets I currently work on and had the maintenance manual documents nearby; but we should have taken the time to go through each step one by one and been more meticulous with accomplishing each task regardless of how long the tasks take. Another contributing factor was the stress that I placed on myself due to time constraint to get the aircraft airworthy and to the gate so it could make its departure time. I was also getting stress from others. The R/H engine transmitter was not in our hands until XA:30 and from approximately XD:00 to XF:30 I got pressure from phone calls by two different chiefs and two different managers wanting to know the status of the aircraft. The third factor is if there's a misunderstanding among crew members; we should convene with each other to figure out what would be the proper actions to take for the task on hand.