Engine spinning backward when killed?

[wanderinthru]

350 Crate, unknown mileage year etc.. In the race car. Running really well and smooth, or was till it just developed a miss that is yet to be pursued. Idle set at 1100 rpm, timed by ear, I don't have a light. When I kill it sometimes it will just die. Sometimes it just wants to keep on running, sometimes it just dies and spins backward? Any ideas?
Appreciate it guys!!

 

[squaredeal91]

Lol I've had them spin reverse like you say. I think its referred to as dieseling. Exess raw fuel or fumes igniting I guess. I'm not the sharpest tho. As far as the cause goes there are a number of things that can do it. What Carburetor are you running? Maybe engine has allot of carbon on the pistons? Maybe broken valve spring? What is the miss like? Misses only at idle, misses all the time?

 

[squaredeal91]

You said it's in a race car? What fuel are you running? Have you changed the fuel grade at any time recently?

 

[wanderinthru]

Lol I've had them spin reverse like you say. I think its referred to as dieseling. Exess raw fuel or fumes igniting I guess. I'm not the sharpest tho. As far as the cause goes there are a number of things that can do it. What Carburetor are you running? Maybe engine has allot of carbon on the pistons? Maybe broken valve spring? What is the miss like? Misses only at idle, misses all the time?

Holley 2 barrel 500 cfm. Miss is there all the time. The spark plugs nor wires have been changed, wires I need have proven a challenge to find, locally I brick and mortar if possible. The miss isn't what I'm dealing with now, need it to not spin backward when it's shut down. It did it prior to the miss showing up.

 

[fast 99]

Idle speed too high? Add a idle solenoid if it won't idle slow enough.

Octane too low, overheating?

Really need to fix it soon. Dieseling or running backward can cause immediate damage.

 

[squaredeal91]

I bet it's evacuating the oil every time leaving you with a dry start. Very odd

 

[CalSgt]

running backward can cause immediate damage.

LOL... I managed to stall a toyota truck on a steep hill out hunting one day. Before I knew it I had stabbed the clutch in just the wrong timing to end up push starting the truck while it rolled backwards. Damn thing fired up and ran that way, sucker had five reverse gears and a forward gear where reverse should be. I quickly turned it off and restarted with the starter, thank goodness it didnt break anything. That would have been a long walk back to civilization.

 

[fast 99]

LOL... I managed to stall a toyota truck on a steep hill out hunting one day. Before I knew it I had stabbed the clutch in just the wrong timing to end up push starting the truck while it rolled backwards. Damn thing fired up and ran that way, sucker had five reverse gears and a forward gear where reverse should be. I quickly turned it off and restarted with the starter, thank goodness it didnt break anything. That would have been a long walk back to civilization.

My 2-cycle motorcycle would regularly do that but only when real warm. 2 cycles are simple but with oil injection could still damage it.

Have seen 4 cycle engines run backward usually for just a couple seconds while winding down, not good. Dieseling, pinging and other similar issues were very common during the 80's-90's. Fuel was being re-designed, octane lowered, and manufacturers needed to meet emissions.
TBI fixed most of that.

 

[rusted nuts]

Holley 2 barrel 500 cfm. Miss is there all the time. The spark plugs nor wires have been changed, wires I need have proven a challenge to find, locally I brick and mortar if possible. The miss isn't what I'm dealing with now, need it to not spin backward when it's shut down. It did it prior to the miss showing up.

sounds like too fast idle, And timing to advance. I would pull the plug on the dead Cly and see what it looks like , Do a compreeson test too.

 

[DoubleDingo]

@wanderinthru Are you looking for the plug wires that can be routed underneath up close to the engine block?

 

[Buck69]

Is there some kind of load behind your engine that bumps it backwards when it comes to a stop?
Asking cause this is a common occurrence with a carbureted jet boat that has it's ignition cut while hot and above idle.
Likely, your miss (high idle also contributing) is putting unburnt fuel into the exhaust. If your engine gets a slight bump backwards, hot spots from deposits (fouled plugs) in the cylinders it all it takes for ignition.
Over advanced timing can contribute to higher cylinder temps, but I would think it would have no influence to kicking the engine backwards. It is out of the picture once the key is shut off.
I would start with new plugs, cap and rotor.

 

[wanderinthru]

@wanderinthru Are you looking for the plug wires that can be routed underneath up close to the engine block?

No sir straight boots on the plugs and cut to fit at the dizzy. It has Camel Humps on it and I want to keep them away.

 

[wanderinthru]

Believe I got the miss figured. Cranked it and went to pulling wires on the side the miss was on. Number 4 lit me up like they put me in a DC Old Sparkey! Throwed another old junk wire on there and she leveled out. I believe it's just to lean, Come to find out the main jets are for 70 degrees at sea level. I'm at 4300 feet so I need bigger holes. Now...to find those....or the right drill bit.

 

[DoubleDingo]

No sir straight boots on the plugs and cut to fit at the dizzy. It has Camel Humps on it and I want to keep them away.

Gotcha. If you're meaning the center dump manifolds, straight boots do work, but 90 degree boots and running the wires next to the block works too. Probably not ideal while at a pit stop at needing change or check plug wires. I always ran the straight boot kind, but the last set I bought was a cut to fit to run the wires against the block. I always had issues keeping them from getting too close with the straight boots. Against the block they were no where near the exhaust.

 

[Turbo4whl]

Believe I got the miss figured. Cranked it and went to pulling wires on the side the miss was on. Number 4 lit me up like they put me in a DC Old Sparkey! Throwed another old junk wire on there and she leveled out. I believe it's just to lean, Come to find out the main jets are for 70 degrees at sea level. I'm at 4300 feet so I need bigger holes. Now...to find those....or the right drill bit.

Best not to drill the Holley jets. Two reasons, the jets have a radius around the hole. When you drill them this is gone. Second, the jets may be coated for corrosion protection. Some jets were bronze, no coating.

Back in the day speed shops would have a large divided box with all the different sizes for the Holley's. You can still order what ever size you need now. Best part then was if you weren't happy with what you tried, and you did not goof them up, the shop would swap you for free, another size.