Video I saw on MySpace. Thought you all might enjoy it. Apparently, the people in attendance think its the greatest thing they have ever seen. They are screaming like they just looked into the eyes of God himself!! lol

http://vids.myspace.com/index.cfm?fu...deoID=23812769

 

Way to float the valves....

 

No it's at the end when he's reving it up spraying the crowd, sounds like he's flooring it and holding it there, it starts to sound like it's missing... cause it is missing, valves aren't able to open and close fast enough, they are just floating.

I think the clicking noise you are hearing is just the sound of the exhaust gases pounding on pipe. In real life you don't hear it because it is to loud. But a camera has built in noise reduction that keeps everything with in a given maximum range.

 

They're just staying open. "Floating" in place. The mechanism that closes the valves can't keep up with how fast the engine is revolving (the RPM's are too high). The springs that close the valves don't have enough force to close the valves before the next revolution occurs and the lobe of the cam comes around again to open the valves. So when the cam is in the full valve close position for a certain cylinder, the rods, or whatever lifting mechanism is being used, aren't touching the surface of the cam anymore, essentially "floating" away from the cam until the lobe hits it again to open them, but they are already open from the last revolution.


If that makes sense

So in a nutshell, the valves don't close all the way because the RPM's are too high and overpowering the springs, and the valves can't seal so you lose compression, then ignited fuel can start traveling through the headers and exhaust system.

If I messed up anywhere, please correct me if I'm wrong. It's awfully late to think about this stuff

 

Interesting what people will do to draw some idiotic attention to themselves.

 

So is floating valves what happens when u put a crazy size cam in a motor and u get that distinct idle that a motor with a huge cam has?

 

No, you can float any engine, push rod engines typically float before a roller, or OHC (Over Head Cam).
Floating is not a good thing. You are way past the redline....... Typically your tach is going to be pegged, if it's floating and your not reved out, then you've got weak valve springs or bent push rod.

Floating an engine, you are on the verge of grenading it. It could blow up at any minute. First thing that happens is you will likely bend the push rods, the engine will still run afterwards, but you lose a lot of power.

If an engine is built for 7K rpm, then stronger valve springs will be added or upgraded to keep up at that RPM, or if other valve system, it will be built or upgraded to keep up.

 

Yeah but a stock engine has rev limiters so it's nearly impossible to bust a governed engine... or else when I put my garden tractor to full throttle, I'd be grenading my engine everytime I mow the lawn.

 

That is true.

Although..... years ago, my dad gave my brother his old lawnmower to use as a go kart. My brother, probably 6-7 at the time, took the deck off and found what he called "the turbo"...

He tied a string to the throttle on the carb so he could pull it to true wide open throttle until the fuel bowl ran dry. (The fuel pump couldn't keep up)
But I never heard it float..... I'd say proportionally, the valve springs on a lawn more are stronger and they don't open as far, so don't have to travel as far to open/close. Also I'd say proportionally all parts are stronger because they aren't exposed to the same amount of forces. Also probably it is built to go more RPM's than what the carburetor will allow it to. The carb it's self is a governor because it cant deliver enough fuel/air to make it float. A larger, more CFM carb it would still float eventually.

A 20 hp single piston engine is only going to push down on the piston with a maximum of 11,000 ft lbs per second. A 300 hp engine is 165,000 ft lbs per second /8 = 20,625 ft lbs per second per cylinder. That's quite a bit more force on each part, then the bearings, pistons, rods etc on a lawn mower aren't that much smaller or thinner etc.

Hmm interesting I had never thought about it that way.......

 

Sounds like he was banging against the rev limiter pretty good.

 

I'd doubt that it has a rev limiter on it.

I'd guess that it's likely even carburated, probably even distributer with electronic ignition.

Now computer module at all......

It'll rev until the carb(s) cant give it anymore air/fuel or the valves cant keep up or it blows up, which ever comes first.

 

That sounds like one bad a$$ motor. I sure as heck would put a rev limiter on it.

 

Why?
People here buy tuners for their 150's just to get rid of the rev limiter.

It doesn't take a genius to either shift or lift. The guy was just a tard he got caught up in the moment putting on a show.

 

He probably spent several thousand on the motor judging by the rest of the Jeep.

A few hundred $$ is well spent to protect $5K, or whatever he spent.

 

I think it's just to raise it higher. I know I wouldn't totally remove a rev limiter on any of my vehicles. Maybe bump it up a few hundred RPM's but never get rid of it.