I have done a rebuild on my 360 and the timing is advanced almost 40 degrees. Has anyone had this problem?

Here is what is in the engine new:
crank
cam (RV)
Piston & rings (30 over)
lifters
valve job done to heads
oil pump
water pump
alternator
power steering pump
timing chain and gears
cam gear
distributor and distributor gear
I did the valley oil pump mod
intake with TBI
MSD ignition and coil

I am at a lost with why my engine is so far advanced. When driving around town it gets "loaded" up and will back fire a couple of time if you try to get on it (I figured due to the advanced timing). Once you stay in it it runs fine. Any help is greatly appreciated.

Brad