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Author Topic:   Anyone ever play around with Controlled Valve Float?
Xtreme12x
Dirt Forum Champ
Total posts: 874
posted December 29, 2004 03:05 PM  
In the kart motors i build, we have to get the valves to float just right to get the max hp. I've been wondering if there was anyone that has done it or tried it.

sdhnc29
Dirt Forum Champ
Total posts: 934
posted December 29, 2004 09:54 PM  
Back years ago we did some engines in California for a guy who ran a C Econo dragster. This was 302ci Chevy engines that turned around 11,000 rpm (not much "econo" about them). This could be considered controlled valve float, as we were using the piston's to close the valves. I'm assuming this is similar to what your doing with your go-kart's.
Steve

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

goinrcn44h
Dirt Freak

Total posts: 205
posted December 30, 2004 09:18 AM  
sounds to me she'd be good for just about a quarter mile......... TOPS...
I'd like to see a shade more longevity, but hey, thats just me.. wanna see some rpm just build a 2-stroke V-8, then I might be able to tune the dang thing and keep em together..lol
44H

rico 08
Dirt Forum Champ
Total posts: 1139
posted December 31, 2004 06:38 AM  
I don't see how this works,it's my understanding that each time you float the valves due to the stress that they will float at a lower rpm the next time,it may only be 50 rpm or so..so if this is true you will eventually end up with a lower valve float rpm each time...right?

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted December 31, 2004 08:56 AM  
Here is how we do it in Go karting...
What the rules state is that the max lift of the cam can be only .233... well we'd like to get more then that but it'll never happen, and the general exhaust spring coil binds at around .360 give or take .20 thou. The camshafts are ground into the spec rules we run, as we are checked every .50 thousandths across the dial indicator, with fast ramp rates, we set our valve spring presures, installed height, and coil bind to accheive the perfect float at a certain rpm. On a restrictor plate motor we run arounh 16 pounds on the intake and 15 on the exhaust for spring pressures... unrestricted anywhere from 18-20 on the intake, and 17-20 on the exhaust. And these springs are one coil only. Once you get to a certain RPM your Intake Valve only, floats and just touches the head, since these are flathead motors... and leaves a little mooneye on the head. This creates more hp, and torque. KP Knows what i'm talking about in all of this. You'd have to spring your valves right, it would take a different cam setup, and then probably stronger parts in some area's, but you actually get the lifter to land right at a certain spot on the camshaft every time... controlled valve float, now if you have it set up for maybe 6900 rpm and turn 7500 your going to float both valves and waste your time...

goinrcn44h
Dirt Freak

Total posts: 205
posted December 31, 2004 03:01 PM  
I assume you are dealing also with a single cylinder at most two. 8 times easier to compensate for variables, flex, stretch, etc. anything in theory is possible, its the application process that is the sketchy part.
I've seen some things in 2-strokes and now in the 4-strokes that have been hitting the market the last 4 or 5 years that is just mind boggling for rpm, compression, etc.. not to mention technology overall.
44H

rrrrick
Dirt Maniac

Total posts: 192
posted January 05, 2005 12:51 PM  
I have heard of some cam maunfactures for restricted cam lift classes that use very aggresive cam ramp angles to launch the lifter to higher then spec heights. I forget which cam manufacture was making those cams though.

[This message has been edited by rrrrick (edited January 05, 2005).]

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