Had my 76 (or so) 460 running this summer. Just needed to tweak my carb a bit (770 Avenger) and get some exhaust built so I could get it running just right. One day lately when I went to start it, it would bairly turn over (very slow and jerky). It seemed when I had full 12 volts it would turn over a bit but not enough to fire. When the battery voltage drops a bit under 12 volts I would get a grinding sound from my solenoid. I replaced the solenoid, new solenoid did the same thing, bypass it, same thing. I thought my starter may have cooked from my open exhaust and may be having trouble turning it over. I replaced the starter with no luck. Truck was low on antifreeze, so I thought maybe I warped or cracked a head and the antifreeze was gumming things up. drained the oil and it looked ok..(What would it look like if it did have antifreeze in it? Could I tell?) If I hook up two batteries together (24v), the truck turns over fine (but I'm scared to let it start if there's a problem) Why do I need so much juice to turn this thing over all of a sudden? I have tried other batteries that I know are good.
Please...anyhelp with this would be appreciated. I am no pro at troubleshooting engine problems, especially this one.
Thanks.

 

A fully charged battery will read from 12.4 to 12.7 volts. At 12 volts the battery is flat. With the starter turning the voltage should never drop below 10.5 volts.

 

Sorry, what I meant by 12v is that it's fully charged. It reads as high as 13 when on the charger. 12 should still turn it over anyway shouldnt it?

 

On the charger should read 14 to 14.5 volts. After the charge is done and a wait of an hour or two, battery should read close to 12.7. A battery, just sitting there at 12 volts is dead flat and if so after the charge is bad. 12 volts before cranking will not get the motor turned over. Check the voltage while cranking the starter, anything less than 10.5 volts is marginal and less than 10 say your battery is not enough amps available (not a big enough battery) or dead.

 

How long has it sat? It may have siezed if it has been a while. If not siezed, the timing may be off, or it may have jumped time (timing gears and chain).

What ever you do, do not hook a straight 24 volts into it. It will fry your vehicle. There is no harm in seting it up with pos to post and neg to neg but a pos to neg setup is just too many volts.

Pull your plugs, make sure there is plenty of oil. Disconnect the ignition completely (no power to any computer or internal circuits). Remove the dist cap. Do not remove dist. Disconnect and block the fuel line or send a return line directly to the filler.

Now see if it will turn over. It should turn over very fast. Watch and see if anything blows out of the cylinders. Also, make sure the dist is turning. If nothing blows out, it is turning over fast, then you are ready for the next step. If the dist is not turning, it has jumped time and probally fractured a gear.

If it is turning slow, there is a bind somehere. This could be anything, but definately internal. It could be anthing from a partial to full teardown for repairs.

Put the plugs back in and then turn it over. If it sounds normal, then hook the ignition back up. Do a rough timing set. Pour a little fuel in the carb, like a capful, that is enough. (NO EITHER). Have fire extinguisher ready and do an attempt to start. Remember it may backfire. If you get a runon, hook up the fuel line and go. If not, sounds like you may be doing a teardown.

 

Thanks guys, I will try this stuff and report back. Before installing this 460 I installed a new timing chain, so it shouldn't be loose, but last time I had it running it was backfiring a bit before I shut it off, hope it is just a timing or dist problem.

 

i have somewhat of a similar prob my 460 turns over just fine no matter what temp the first time but if i turn it off it goes errrrrrrrrrruuuuuumphhhh.......................... ...................................errrrrrrrrrruuu uuumphhhh and then it starts but its odd to me that it starts just dandy but after that for whatever reason it can barely turn over if like i drove a mile to the store and then came out to go back home