Timing “180 out”?

[76zimmer]

I dont understand how an engine can even run “180” out?
Both valves are probably partially open when spark occurs right?
I guess I’ve never had one “180” out before.

Someone makes sense of this old wives tail for me….

 

[Wes Harden]

I have never had 1 run 180 out.

 

[1-ton]

It might run for a couple of seconds. Every time the engine fired on the compression stroke the partially opened intake valve would send burning fuel right up the intake manifold, and starve it of air, thus shutting the engine down.

 

[nvrenuf]

I’ve mistakenly set one at 180 out but it didn’t run, it just popped, farted and complained.

 

[streetrodchev]

I’ve not had one run at 180 out.

 

[shady]

The 180 part they mean I think is when the #1piston is up, but the it's not the compression stroke. I think you can get em to pop that way, but it's ugly.


Another wives tale is that the dizzy has to be dropped in a certain way, with the rotor pointing to cyl 1.
For looks maybe.

Drop the dizzy in, however the rotor falls to line up with the pump. (Cyl 1 @ tdc of course). Then start putting wires on with number 1 being the dizzy point that the rotor is pointing at. Runs like a charm. It's the exact same thing. Just the wires are in different places on the dizzy than you'd normally see.

Been doing this for years now. Fork trying to get the pump drive setting just right and all that. Lol.

 

[Blue85]

Keep in mind that the diagram in the first post is a single circle representing 2 engine revolutions, so you don't actually have both valves open at BDC. Plus, that doesn't matter, because you're still firing at TDC (180 on the dizzy is 360 on the crank). While you normally fire between the "squeeze" and "bang" strokes (intake valve is closed, exhaust is starting to open), 180 out has you fire between the "blow" and "suck" (exhaust valve is closed, intake is starting to open). Essentially it's a very low compression engine when firing out of the intake valve, but to run/idle only takes a small amount of piston pressure. The engine still makes vacuum (whether you have any spark or not...) which will draw air/fuel in, but as stated earlier, getting exhaust gas in the intake manifold can easily reduce O2 levels too low to run. (Plus the fire in the intake/carb tends to rob O2 ).

I think the reason it can run at all is that you don't spark at TDC, it occurs sometime before that - approximately your base timing + some of the vacuum advance (if not a ported source). So if that advance is similar to the cam profile, the cylinder may still have some pressure when the spark comes. So different cam profiles and different amounts of advance may explain why some people report it kind of running momentarily.

 

[Blue85]

Another wives tale is that the dizzy has to be dropped in a certain way, with the rotor pointing to cyl 1.
For looks maybe.

Drop the dizzy in, however the rotor falls to line up with the pump. (Cyl 1 @ tdc of course). Then start putting wires on with number 1 being the dizzy point that the rotor is pointing at. Runs like a charm. It's the exact same thing. Just the wires are in different places on the dizzy than you'd normally see.

This is true, but there are sometimes mechanical limitations. For example, the vacuum can on a big-cap HEI can easily hit the firewall if the position changes too much. I have a TPI setup and that big plenum limits the range the distributor can sit in.

 

[shady]

Outside of the dizzy stays in normal orientation. It's just the wires that end up in weird places.

 

[6872xtc]

I never set one up 180* out at the cam or distributor, BUT! I did plug the wires onto the cap in the wrong rotation once! (counterclockwise) It ran, but popped both through the intake and exhaust! Swapped back to clockwise and all was fine!

 

[shady]

I did that on my buddies Cordoba once lol. Only figured it out when we tore it all off and started over

 

[tRustyK5]

The 180 part they mean I think is when the #1piston is up, but the it's not the compression stroke. I think you can get em to pop that way, but it's ugly.


Another wives tale is that the dizzy has to be dropped in a certain way, with the rotor pointing to cyl 1.
For looks maybe.

Drop the dizzy in, however the rotor falls to line up with the pump. (Cyl 1 @ tdc of course). Then start putting wires on with number 1 being the dizzy point that the rotor is pointing at. Runs like a charm. It's the exact same thing. Just the wires are in different places on the dizzy than you'd normally see.

Been doing this for years now. Fork trying to get the pump drive setting just right and all that. Lol.

Pump drive is the easiest part. Set the dist where it should be, and bump the engine...the dist will drop onto the pump drive as soon as it lines up. I don't even look in the damn hole anymore.

I have never seen an engine with the dist 180 out run. Ever. Each cylinder is trying to fire on the exhaust stroke, and there ain't any compression.

 

[Fastereddie]

All right, I got one for ya. When I was out wheeling a couple years ago in Logandale I had the magnum in low and the 205 in low. Had the 465 in like 3rd I think. Was lugging it over some sandstone fingers.
Idling up one of them, I stalled it and it rolled backwards before I could push the clutch in, it fired up and was running backwards! Took me a minute to understand what the hell was going on. It was snorting like a dragon out the air filter!
Craziest thing I ever seen. I restarted it and it was idling real high, so I shut it off again. Popped the hood and looked around and found it had blew a big 3/8 vacuum plug off I had on the intake.

 

[imiceman44]

It might run for a couple of seconds. Every time the engine fired on the compression stroke the partially opened intake valve would send burning fuel right up the intake manifold, and starve it of air, thus shutting the engine down.

That's what happened with me, it would backfire through the intake and once it caught on fire

 

[Chickntrk]

The 180 part they mean I think is when the #1piston is up, but the it's not the compression stroke. I think you can get em to pop that way, but it's ugly.


Another wives tale is that the dizzy has to be dropped in a certain way, with the rotor pointing to cyl 1.
For looks maybe.

Drop the dizzy in, however the rotor falls to line up with the pump. (Cyl 1 @ tdc of course). Then start putting wires on with number 1 being the dizzy point that the rotor is pointing at. Runs like a charm. It's the exact same thing. Just the wires are in different places on the dizzy than you'd normally see.

Been doing this for years now. Fork trying to get the pump drive setting just right and all that. Lol.

Agree, way too much thought put into that sometimes.

 

[Chickntrk]

All right, I got one for ya. When I was out wheeling a couple years ago in Logandale I had the magnum in low and the 205 in low. Had the 465 in like 3rd I think. Was lugging it over some sandstone fingers.
Idling up one of them, I stalled it and it rolled backwards before I could push the clutch in, it fired up and was running backwards! Took me a minute to understand what the hell was going on. It was snorting like a dragon out the air filter!
Craziest thing I ever seen. I restarted it and it was idling real high, so I shut it off again. Popped the hood and looked around and found it had blew a big 3/8 vacuum plug off I had on the intake.

Saw this happen on an 8v92 Detroit once, sum bitch took off and ran backwards.

 

[Capt Ron]

Saw this happen on an 8v92 Detroit once, sum bitch took off and ran backwards.

Those engines are actually designed to run either way. We have one in an off road truck. Has provisions for a starter on both sides of the engine. Remember old movies and the guy on a ship yells " reverse engines" ? That's what happens, actually shuts off engines and restarts them going the other way.

 

[1-ton]

Being that production line vehicles have not come with a distributor for over 20-years being able to properly install a distributor is becoming a lost art.

 

[Chickntrk]

Those engines are actually designed to run either way. We have one in an off road truck. Has provisions for a starter on both sides of the engine. Remember old movies and the guy on a ship yells " reverse engines" ? That's what happens, actually shuts off engines and restarts them going the other way.

Yep, it’s just weird when it happens as quick as it did, I also love to see guys run away when you take one to full throttle….we had a 12v92 in a snowblower that had an either start system….couple shots and when she fired everyone scattered. Gotta watch the rack doesn’t stick on those old girls….

 

[Blue85]

it fired up and was running backwards!

2-strokes are relatively easy to run backwards. A lot of snowmobiles have employed reversing engines to eliminate the need for a reversing chaincase.

Being that production line vehicles have not come with a distributor for over 20-years being able to properly install a distributor is becoming a lost art.

What I miss are the timing marks. There are times you mix and match parts and just need to know the actual physical timing and not just what the computer thinks it is.