Reverse Rotating An Engine ?

[billt460]

Let's say a NASCAR Cup Car spins at high speed. And the driver doesn't get the clutch in fast enough, but get's off the throttle, and it kills the engine. And it starts reverse rotating, from traveling backwards at high speed, while still in high gear with the clutch out. Will that screw stuff up internally?

 

[spasm3]

Reverse rotate? How?

Some timing chain steups are designed for one direction only, make sure you are turning the engine over the right way with a wrench.

 

[WylieCoyote]

I've read that some engines have enough slack in the timing chain that the piston can come in contact with valves when rotated backward. Can't imagine a timing chain being that slacked, but I'm no engine assembler.

Maybe not such a problem when doing it with a wrench, but could be damaging at speed.

 

[ARCOgraphite]

Let's say a NASCAR Cup Car spins at high speed. And the driver doesn't get the clutch in fast enough, but get's off the throttle, and it kills the engine. And it starts reverse rotating, from traveling backwards at high speed, while still in high gear with the clutch out. Will that screw stuff up internally?

We used to improve our skills with the what we called a power 'in-Lane' U-turn. Its also intimidated other plebeian drivers - and as a near psychotic and over-zealous youth we like doing this in our cars
My feet don't dance that way where I would leave the car in top going backwards. I was always spinning the tires coming out of the 180 this way.
Back to Cup engines. Given the very close piston to valve clearances, Typical NASCAR 280 deg. cams (at .05") and 2/1 rockers I bet it wouldn't be pretty. The VT is belt drive. Also the fact they use VERY wide rod side clearances and they would not want to spin backwards either.
Why do you ask? got a little bet going?

 

[billt460]

Why do you ask? got a little bet going?

No, I just wondered. You see so many "Big One's" these days on the Super Speedway's. And in the process you see many of these cars get turned backwards at well over 150+ MPH. And in several of them you see the white lettering come to a stop, and sometimes start turning in reverse. Albeit for just a few revolutions before the driver locks up the brakes..... Or else piles into something or someone. So you don't really know if turning the engine in reverse damaged anything internally. And I've never heard an announcer comment about it.

 

[ARCOgraphite]

No, I just wondered. You see so many "Big One's" these days on the Super Speedway's. And in the process you see many of these cars get turned backwards at well over 150+ MPH. And in several of them you see the white lettering come to a stop, and sometimes start turning in reverse. Albeit for just a few revolutions before the driver locks up the brakes..... Or else piles into something or someone. So you don't really know if turning the engine in reverse damaged anything internally. And I've never heard an announcer comment about it.

The new next gen cars are a big change
with independent rear suspension, rear mounted 6 speed transaxle with sequential gearbox, front coilovers, etc ...

 

[High Performance Lubricants]

This is not unique to NASCAR. It is something I have always wondered myself. We see it in the World of Outlaws as well. I have not ever seen a case where it made a difference. I cringe at the thought of the oil pump running backwards drawing oil off the crank. It seems to not be a major factor.

 

[billt460]

I remember reading once that Smokey Yunick built a purpose engine that rotated backwards. The concept was one that he believed in. In that an engine rotating in the opposite direction would use engine torque to an advantage in turning left, instead of working against the cars ability to steer in that direction.

I believe NASCAR put a stop to it, and never allowed it to compete, because at the time such an engine didn't exist in modern production cars that NASCAR was based on. Interesting concept though. Yunick was decades ahead of his time. The man was a mechanical genius of the highest order.

 

[earlyre]

I remember reading once that Smokey Yunick built a purpose engine that rotated backwards. The concept was one that he believed in. In that an engine rotating in the opposite direction would use engine torque to an advantage in turning left, instead of working against the cars ability to steer in that direction.

I believe NASCAR put a stop to it, and never allowed it to compete, because at the time such an engine didn't exist in modern production cars that NASCAR was based on. Interesting concept though. Yunick was decades ahead of his time. The man was a mechanical genius of the highest order.

didn't he also build a whole car to 7/8 scale of the real thing?

 

[billt460]

didn't he also build a whole car to 7/8 scale of the real thing?

That was never proven because NASCAR didn't use certified templates to check bodies back then...... Except the one that Smokey made. And it was a 1968 Chevelle I believe, that was never raced. He did get caught with a oversize diameter fuel line, that held almost 2 more gallons of gas, that allowed his driver to win a race by not having to come in with the leaders for a "splash & go".

Technically he wasn't "cheating" because NASCAR never specified what size the fuel line had to be. He knew NASCAR would tear the car down, and after they removed the fuel tank, he got in started it up, minus the gas tank, and drove it to his garage across town. Many say most of the NASCAR rule book was written because of what Yunick did to exploit it to the fullest. NASCAR just wasn't ready for a guy like Smokey. This is a good video that explains a lot of Smokey's "cheating".