humm, is my car supposed to move?

[Roa, Greg]

Ok, here's one for the experts.
On my semi-newly aquired 87' 5kcstq, the parking brakes are non functional.  I've freed up the actuators, and have new e-brake cables at the ready, so this won't be an issue for much longer.

Question is, when I park the car on a hill (nose down), and place the transmission in reverse (how I typically leave it parked), the 5k will occasionally lurch forward a few inches.  On a steep hill, it will lurch forward every 5 seconds or so.

I always use my parking brake on my other cars, so I've not seen this happen before, but I don't remember this being an issue on the 4k's.

Is the creeping a result of:
The heavier type 44 body against the same displacement engine?
The lower compression of the MC engine?
Or, a problem with the engine, such as excessive leakdown, bad valve, ect?

Any ideas?

Greg Roa
Cincinnati, OH
86' 4kcsq x2
87' 5kcstq
93' 90CS
83' 944