Here's the problem...when I adjust the timing till it's running perfect, it won't start. when I adjust the timing to where it will start, it runs super rough. When i got this truck , plug wires 3 and 5 were revesed on the distributor cap, but it ran. The previous owner adjusted the entire engine to support the reversal. I am on the verge of straightening this out but I can't seem to figure this out. My truck is an '85 300 I6, C6 trans 1bbl carb, all stock, hydraulic lifters. Any help will be appreciated.
<!-- / message --><!-- sig -->

 

I didn't have anything jump out at me but I wonder if the timing chain has jumped or is bad.

 

Are you timing the engine with the spout connector disconnected? There's a wiring pigtail connector down around the distributor that has a jumper plug stuck into it. pull that plug out and set the timing to 10 degrees BTDC. Then re-plug the spout connector and see what happens.

Something to remember: Depending on the age and mileage on your 300, it's possible that the rubber hub in the harmonic balancer on the end of the crankshaft has slipped, which throws the factory timing marks on the rim of the balancer off. If you have trouble timing to the factory marks and to see if this is the case, turn the engine over by hand until the distributor rotor is pointing to the #1 plug wire on the cap. Remove #1 spark plug and look into the cylinder to see of the piston is at TDC (you can stick a plastic straw into the cylinder thru the plug hole, then "rock" the engine back & forth by hand until the piston is at TDC). Then look at the timing mark on the balancer on the passenger side (the marks on the driver's side are meaningless) and see if anything lines up with the marker on the block. If so, the hub hasn't slipped. It not, paint a thin white line ("white-out" works well) on the rim of the balancer in line with the mark on the block, and use that as your timing reference.

The spout connector disables the EFI equal of the "vacuum advance" when the connector is unplugged.

 

Is there a spout connector on the carbed engine?

If it has mechanical advance the weights might be stuck.

 

the 300 does not have a timing chain. it uses a gear

 

The spout connector is down by the distributor. It's black and about 3 inches long on my '86. Disconnect the spout connector, start the engine and set the timing. Shut the engine off, and reconnect the spout connector. Make sure you're shooting the right timing marks. They're on the left side of the engine as you face it. The ones on the right side are left over from earlier models, and were never removed from the cover. I know, two sets of timing marks is weird. Confusing too!

 

on EFI models where is that connecter yer suposed to unplug???....i looked and looked and i can't find it

 

Thanks for the replies , checked dampener, hasn't slipped but check tdc to timing marks anyway. Timing marks did line up. Re-timed (with sprout connector disconnected). Starts great cold, runs great, but.... after it is warm and shut off if cranks but won't start. To get it to start I must loosen the distributor and back it off alittle, then it will only start after the starter disengages.

Any help will be appreciated. Merry Christmas

 

Now that you have the timing set, it is what it is. The truck may be running rich. When you're way too rich, the engine will start when cold because it needs the rich mixture. As long as it is running, it will tolerate it, but once shut off, the rich mixture is too rich to restart. When the truck is warmed up good, turn it off and check the spark plugs and see if they're wet. They may be gas-fouled.

 

It might also be time to think about adjusting or rebuilding the carburator. If it hasn't been done for quite awhile then you might have a leaky gasket or adjustment problem.

 

This is a bit unusual but I have seen a bad ignition switch cause a no-spark problem while cranking and as soon as you let off the starter it gets spark and fires up. Have a helper check for spark during the cranking mode and see if it comes back as the ignition switch returns to the "run" position.
Joe