Electrical Nightmare!

i have a 1970 Chevy c-10, my dream truck. well my dream truck seems to have a mind of its own and not want to start for me. I bought a whole new engine wiring harness, 2 new starters, a brand new battery, a voltage regulator, and an alternator....STILL when i go to turn the motor over it seems as if my battery is dead or it turns s l o w l y until it seems like it catches up and fires up. Now its not the original motor. its a 1973 350 corvette motor. does that have anything to do with it? anyone have any thoughts or answers send them my way because im stuck! thanks  

It sounds like you have a bad ground, if all of the wiring is new along with the battery and starter, this is where I would check first.  

Yeah sounds like a ground to me too. Check the ground strap to the motor to see whether the surface is clean. To check, run a direct ground straight to the starter motor so you can cancel out a bad ground problem, plus make sure you have a ground from the chassie/firewall to the motor also, this will ground out the gauges etc. Also make sure you have a good power signal from the ignition key.I would jump the solinoid from the starter to cancel out a possible ignition problem.Just bypass the ignition and jump the starter direct from the battery. This will be a great start point.
 If this is not a silly question...Did the motor turn over before you changed the wiring? Put a bar on the crank to check that the motor turns.  

the motor ran fine until about Winter came along and it just got worse over the months. Now the motor does have a big cam, could that be the reason why its not turning? now when you mean the motor having a ground you mean the battery ground wire? or Does the motor actually have to have a ground wire connected to it and to the firewall? because im almost positive my motor does not have a ground wire on it.  

I don't think it is the cam. the truck started with this cam before right?

Everything needs a ground... so the battery should be grounded to clean bare metal (all grounds should be bolted to clean bare metal) either bolted on to the motor or the Frame. Then the frame and the motor should have a ground strap to insure that the ground is transfering between the two. Don't rely on the motor mounts for this... And finally the ground needs to be transfered to the cab, so a third strap needs to run from the frame, or motor to the cab.  

All this is correct but you have to start from the battery to cancel out the ignition. As myself and MRGUNKEL have said is what you have to check.So at this stage it is not necessary to turn the key on. First step is to jump a wire or screw driver across the main terminal on the starter motor( that is the one that has the main cable on the battery attached to) to the smaller terminal(which will activate the starter). You may have 2 small terminals depending on the style of starter, usually it is the one closer to the engine block.
 By doing this you are giving the motor direct power from the battery. If this doesn't work you either have a solinoid problem,weak cranking power of the battery or you did mention something about WINTER(How long has the motor sat? Are you sure you haven't got moisture in the bore and stuck the rings to the side wall. CHECK THAT THE CRANK TURNS BY HAND, if not shoot some MARVEL MYSTERY OIL down the bore and leave for a few days.  

I was reading the posts and wondering how you made out? I have a few more things no one mentioned. Electrical is first as the other guys mentioned. Don't be shy about the ground that came stock on the truck (clean and tight). Then consider adding another one to connect the frame and the engine. The cable should be the same size as the other battery ground cable to carry the cuurrent needed for starting. A good sized wire like 12 ga. for the cab to either engine or frame will work fine.  Hard cranking can also be caused by other things. First of all, since you mentioned getting worse as the weather cooled off, what weight oil is in the engine? 20W-50 is too much for almost any weather. If you are in a winter climate use 10W-30. Continuous high engine rpm is what heats up and ruins oil. This rarely an issue for anything that lives on the street below 5000 rpm constant. Another reason for hard cranking is ignition timing that is too far advanced. If the engine seems more powerful than it did before, even slightly, the timing could have changed somehow. If you can check the timing you could consider that also. There are at least a few reasons for the timing to change and that would take some detective work. One last thing, if this were a gradual problem it could be very serious engine damage such as a crankshaft bearing binding. This would also make noise when the engine gets warmed up. Since you did not mention any knocking from the engine don't worry about that just yet. My guess based on your description --- timing too far advanced.  

hey did u ever get this fixed? sometimes you had to shim these starters to correct clearance between starter drive and flywheel.  

i had the same promblen in my 72 chevy 4x4 had a big cam and it turned over very slowly it was the ground on the back of  the engine to the firewall and i put a one wire altrnator there is no plug in u just put a wire directly to the battery to charge