my theory of valve float

[Bad92GT]

Its been a while now since I had installed my cam, heads, and intake. Through all the hard hits i've given the motor at high RPM's (excess of 6k, and on stock bottom end) i've yet to experience the famous valve float your suppose to get at those RPMs.. i've read many posts about it and still wondered how I manage to slip through the fine line.. Talking to a old school friend of mine, he was saying that the solid tappet motors may not rev like a roller but they can be run alot harder than a roller because valve float is way the hell up there for a solid tappet.. So I think i've managed to figure out what and why i've managed to slip through it.

My cam is the Crane 444221 2021 cam, it's: intake .533 / exhaust .544 lift cam with 1.6 roller rockers.. valve float 6k.. power band 2000-5500..

While running it at the track i've pushed it harder than 6k while pulling even harder than it was supposedly good for. In my combo, I had forgotten one thing to order and that was a set of roller rockers. I wanted to get it running so I just decided i'd throw some on at a later time.. Well that time has never come and i've been driving it since. The only reason I could come up with why the motor doesn't have the valve float it's suppose to is because of the stock rockers.. basically taking away some of the "Rollyness" lol It's the only reason I could think of. And i'm certain that the motor has yet to because it was pulling other cars at the time it hit 6k.. Jrichker or any other really smart guy care to elaborate on why I could slip through it? Sorry its long, but hey.. i'm off work, tired.. and have nothing to do lol

 

[Daggar]

My initial thought is that your tach is off. Unless you've done something to remove the stock rev limiter, you'll hit "the wall" at 6250 RPM.

 

[Bad92GT]

Well i have an aftermarket tach on the column right now.. i hit a couple ticks over 6k.. which is a good ways out the power band and some over valve float..

 

[tony91723]

I thought valve float had to do with weak valve springs? ::

 

[R2D2]

who said you float valves at 6000

 

[emagdnim]

Its all about the valve springs baby!

 

[86bluecobra]

yes valve float is basically the valves not closing by the time it is time to open again. Valve float is cause by springs not being able to close the valves in time. It is not uncommon for a vehicle to not experience valve float around 6200rpm. I experience valve float with my sysmax heads just past the 7000rpm (factory tach seems to be about 200 rpm out when compared to my programable shift light) No doubt the spring on those heads is better then the factory set up but at that rpm the lobes were coming around to quick for the valves to close. thats what causes and what is meant by valve float.

 

[Bad92GT]

ahh so it might be my rediculously huge valve springs.. cranes 600lb springs.. i could go alot bigger cam with these springs.. and if i had went with the 500lb they are rated right there where my cam is.. so id basically max out the 500lb.. could the super high rated springs take a tole on the factory rockers?

 

[EMW150]

Valve float isn't necessarily easily detectable. You can have a deterioration in high rpm power as the springs weaken which indicates valve float. That doesn't mean it's popping like they do in extreme cases. The best way to check it is on a dyno. My car will lose high rpm power and I'll notice a decrease in MPH through the 1/4 but I usually don't let it go to the point where it's popping. That's really hard on valvetrain components.

 

[jgfiveoh]

everyone who is interested in valve float should pick up the latest issue of 5.0 and superfords. there is a great article in there about the "spintron" which measures valvetrain stability. they talk quite a bit about float and how the valve train should operate. they also say that it is not only one component of the valvetrain that can cause valve float but rather all of them put together. also if your valvetrain was in harmony you would actually lose power because you are not floating the valves and creating extra lift and duration. check it out for yourselves. August '06 pg 150 Rev To 8,000