[Cracker]

A friend of mine is doing some work on a 351C that is in a Pantera. The heads were professionally rebuilt completely and original intake reused but port matched. The carb was completely overhauled by Pony Restorers in NY to like new (better) condition. Bottom end/pistons/cyliders all looked good and left alone.

Here is the problem. Engine fired right up but had a consistant backfire through the carb. Timing and firing order are right on and it is using the original dual point distributor BTW. A compression check revealed about 130 psi on cylinders 5-8 but goofy things a happening on 1-4. Guage spikes to around 100 and immediatey settles around 50 on 2&4 and 75 psi on 1 &3. The guage works fine on the other side so we think it could only be either:
1) head gasket problem
2) Cam timing/installation off
3) bad cam (it is original though and has never been removed)
4) bad valve components (unlikely due to complete overhaul by excellent group)
5) ??? What would you say???

One more thing - it could almost seem like pressure is leaking from one cylinder to the next on compression test on 1-4. He is doing a leak down test next on that side to eliminate valve train/headgasket/cylinder/ rings options. Thanks!