If you can change your flight to one departing from SFO/IAD/ORD then you'll have a MUCH better chance if making it. The way your doing it now, coming from EWR is a pain. T-4 to T-1 is just a bus trip away. But the problem is, you may have to wait for the bus, T-1 is accross the airport from T-4 so the trip can take 10-15 min on the bus and finally, you must go through transfer security. You'll have to do that anyway but inter terminal security gets MUCH longer lines then same terminal (T-1) security. IMO w delays a big problem at LHR, 1:40 is pushing the envelope