350 rotates then stops
 

i have a small block 350 in my blazer I replaced the intake heads gaskets started the engine ran it for 20 min with no concerns. Tried the next day engine rotates one revolution then stops. The neg cable will spark. The starter is new removed it checked it seems fine battery is new. Replaced the positive bat cable. I can no longer hand crank the engine over is it toast?

pull the plugs,and try. you may have a coolant leak in a cylinder and overnight it filled it up. pull plugs and crank it.

Plugs are all pulled no sign of coolant will turn a bit better with the plugs out almost nothing with the plugs in…sprayed some sea form creep into the cylinders. Could it be something in the wiring…don't understand why it cranks then stops acts as if there not enough cranking power

are you cranking by hand or starter with the plugs out

With the starter

Never seen a good battery cable spark before. Are you referring to the negative connection to the battery? If bad, it can prevent the starter motor from doing it's job under load properly.

So replaced the battery with high cranking battery both batery cables postive and negative and the ground strap. The enging will barely turn over one rotation. Stops and a whining sound air hiss sound came from the stater area the engine will turn over two rotations slowley with the plugs out i can not hand crank the engine as i was able to when i set the timing.....Can the new starter be done it was bench tested and seemed fine. Can the valve train be binding if so how would you check. Is it possible that the valves are set wrong. This engine was running when i started it at start up no noise from the valves seemed fine. Tried to restart a few days later. Im at a loss and becoming despreate and in need of any help or to know if an engine can partially seize?? Which wire carries the current that turns the starter motor? I dont know where to go from here.

are all your grounds thick and connected? you should have the body and the engine connected to each other and to the battery, when i built my k30 a few years ago i made the mistake of leaving off the big negative cable and it was basically doing what your discribing, cranked ever maybe once then slowed to a halt, after a few tries the ground started smoking as i only had one of the little body grounds hooked up.

also make sure your connections are clean where the ground is attaching to the block and body.

maybe take the starter to autozone and have it tested, also try turning over the engine by hand with a socket wrench. if it spins then my guess would be a wiring issure of some sort.

I replaced all the cables the negative ground from the battery is connected to the block with the smaller wire going to the body. New starter cable and new ground strap going from the body to the block attached to the tranny bolt. I'm unable to hand crank the engine after it ran even though it moved when I set the timing I'm at a loss as to why it ran fine and now won't crank I have an older starter I'm going to try but them I'm completely out of ideas

Can you turn the motor by hand at the flex plate or harmonic balancer? if it is very hard or you cant turn it at all the motor is probaly siezed. Sounds like this motor has been a problem from the start according to your other posts. I still think you have a cracked block or some other terminal engine issue. just because the guy you got it from says it ran when he pulled it out means nothing. He pulled it out for a problem most likely in the first place. I hate to be so negative about this but that engine is very suspect.