Folklore says that when a (gasoline) engine is dieseling (running after the key is turned off) it is turning backwards. I was thinking about this today and it is hard for me to see why this would be true. Anyone care comment?

It shouldn't go in reverse it will just 'run' on (forward...)... but there are cases where timing can be advanced too far and the engine will kick back when starting (so being a bit in reverse)...

-D.Idiot

If you lug an old Detroit diesel it will run backwards. Go ahead, ask me how I know this.

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Official Cookie and Mater Tormentor.

Yes, a "dieseling" gasoline engine is usually still rotating forward. But frequently the dieseling session will end with a BrrrrrwWOOOOSHHH as the engine does kick backward and spin that way for a a second.

However- and I wouldn't have believed this if I hadn't seen it myself on several occasions- my Dad used to have a '78 Horizon (VW engine) that would occasionally diesel backward. The really funny thing was that when it would diesel forward, it was rough and shaky and horrible-sounding like a dieseling gas engine always is, but when it would kick backward it would hum and purr smooth as silk at (just guessing) maybe 1100 RPM or so. Yes, it REALLY WAS running backward, and I have NO explanation of how it was getting fuel for the process unless it was burning engine oil leaked past the exhaust valve guides (it did this when the engine was well on its last legs at only 120,000 miles). It would pour pale bluish smoke out the air intake, turning the ignition on wouldn't do a *damn* thing, the oil pressure was zero while this was happening (oil pump spinning backward!), putting it in gear wouldn't do a damn thing (automatic trans, pump spinning backward) and the only way to stop the SOB was to clap your hand over the exhaust pipe until you could feel a solid suction as the engine starved for air, or (as Dad did when he got disgusted with it) turn on the starter and let it gnash the flywheel into submission...

I was never more glad to see a car leave the family than when Dad sold that POS Horizon.

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We were riding on an amusement park tram (an old, clapped-out articlated city bus with all the windows removed) yesterday, and I noticed from the characteristic screaming noise that it was Detroit powered. I commented to my wife and daughter that the sound they were hearing first appeared on earth about 65-70 years ago, once was heard many times a day on every big city street corner, nowadays is rare enough to make a person notice, and will be completely gone from everywhere except vintage truck, boat, and tractor meets in another 10-15 years.

They said they're going to stop asking me to take them to amusement parks if I keep choosing conversation topics like that....

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Well, Condemner Retards magazine did try to warn your dad that the Horizon and Omni were Black Dot — Not Acceptable... *ducking*

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

An old Oliver 88 will do the same. Don't tell my Dad (it is still runing strong in the right dirrection 25 years later!)

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Chris'
Autobody
Restoration
Service

My Pops had a Super 88 Orville tractor too. Last tractor he had when he quit farming in '62.

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Official Cookie and Mater Tormentor.

The older Detroit diesels are a 2 stroke motor. They have no exhaust valves, but rather ports at the bottom of the cylinder.
This is why most if not all of the older Detroits are super charged.
Since the valve timing is less critical on the 2 stroke, they could run backwards. Although while running backwards they would be blowing bubbles in the oil pan, and not oiling the engine...probably not a good thing.
Also, they didn't last as long as the newer 60 series, at about 300,000 miles most were ready for an overhaul. My 2000 Freightliner got an overhaul this year at 950,000.

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66 Valiant, 225.
84 Van, 225.
71 Maxi-Van, 318
60 Valiant wagon, 225
87 Maxi-Van, 318 4spd

you do mean no INLET valves,do'nt you.
all the "71" series engines I have ever seen (2 stroke diesel) have no inlet valves - only a row of ports at the bottom of the cylinder liner that became exposed at the bottom of the piston stroke.
when exposed,a charge of pressurised air from the blower pushed the exhaust gas out through the exhaust valves. (2 or 4 depending on engine)
piston on the rise,covered the row of ports,exhaust valves closed,compression and a squirt from the injector and off it goes again.
see here


regards,Rod

Some of the early Hart-Paar tractors had no reverse gear, but could
be made to run backwards by slowing the motor to a crawl, retarding
the spark and flipping a lever that set a sprag so that the giant flywheel
bounced and began rotating the other way.

Ya know you're right about this. Been years since I've seen one and got that backwards. Thanks.

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66 Valiant, 225.
84 Van, 225.
71 Maxi-Van, 318
60 Valiant wagon, 225
87 Maxi-Van, 318 4spd

Yep. Detroits had 4 valves per cylinder, all exhaust, and another rocker to trip the injector. Running the rack on them was a real PITA.

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Official Cookie and Mater Tormentor.

So will a old John Deere. The new 2 stroke snowmobiles run backwards for reverse instead of a gearbox.

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Thanks Mike

less than half of detroits were 4VH. most are 2VH. the two stroke engine is still current production for the military.
also, the 51 series engines had no valves at all. strictly ported. they were discontinued early.
the best thing about detroits is they can be configured to just about whatever you want, intake/exhaust on the same or opposite side, different governor choices, single or dual oil pump pickups, oval or figure 8 liner ports, 2 or 4VH, std or low compression (turbo) pistons (trunk or crosshead style), hi or lo or even dual starter, #2, 3, or #4 SAE FWH, the list goes on.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.