Need help with troubleshooting
 

Ok I have a 454 engine that was completely rebuilt. New cam, pistons, aluminum heads, roller rockers, bigger push rods, dual plain aluminum intake, 750 Holley double pumper carb, electric fuel pump, MSD high torque starter. We got the engine up and running started tuning on it and everything was great, set the timing so it would fire right up, locked the distributor in place and all was right with the world. That was a month ago. Out of nowhere 3 weeks ago the engine started to becoming a little hard to start and would kick back sometimes when you tried to start it, but the car would still crank after a time or two... Two weeks ago it becomes even harder to crank and the kickbkick has broken my starter housing. $120 to get rebuilt but hey maybe it needed shims and that will fix it... Wrong still more of the same issue. Now we didn't mess with the timing because we made a mark on the intake and distributor and no one had touched it, it's was still perfect and on tdc when we did check. Now to last week it's went completely hatwire! Engine won't crank period broke the starter again. Ordered another one that was good for up to 16:1 compression (my motor is 10:1) hooked it up on a fully charged battery and the engine turns over maybe twice and acts like the battery is dead. Took the battery out put it in my truck it started right up, put it in my grand national it starter right up?? Put the battry back on the 454 and jumped it off with my truck and barely turns over then it kicks back and broke a tooth off the flywheel. What the heck am I doing wrong??

what/how did you set the timing at
Big-block Chevy timing is pretty well standardized unless major modification have been done. The timing on stock 396, 402, 427 and 454 engines is 32-34 degrees total advance at 3500 rpm. This is for an engine with stock camshaft, heads, stroke, and a compression ratio of 10:1.

#2 - ensure battery cables are not less than 1/0 AWG and connections on both ends are wire-brushed and clean.
Makes a world of difference.
You can have custom made 4/0 gauge cables made. Less heat when current is traveling, less power loss. Cable warm when touching?
Lots of power given off in heat.
Recheck timing.

Remove your spark plugs and see if you can turn the engine over by hand, to make sure you're not experiencing a mechanical issue/failure.

I removed the spark plugs and could turn the motor over with no issues. Also turned the key and motor turned over with no real issue just kinda slow because battery was weak

With the plugs back in, disconnect your coil wire so that the plugs aren't firing, and see if that makes a difference for the better. If the engine cranks over more like normal, it's an ignition timing issue. How many degrees before TDC do you have the timing set at now?

4° before TDC right now

An engine without plugs and a high torque starter should spin insanely fast. If it sounds "normal" there is something very wrong.

Was this timing checked the first time the engine was running, or the last time you had it running? Based on the symptoms, the 3 most likely scenarios that come to mind are: ignition timing is off, valve timing is off (timing chain off a tooth or more), or valve lash not adjusted right.