valve float

[LETZRIDE]

ok this is gunna sound stupid...but what exactly is valve float, and how bad is it?

[rdrr96]

Re: valve float

Valve float is an adverse condition which occurs when the poppet valves on an internal combustion engine valvetrain do not remain in contact with the camshaft lobe during the valve closure phase of the cam lobe profile. This reduces engine efficiency and performance and potentially increases engine emissions.

google is great

[TheGr8Schlotzky]

Re: valve float

It's mostly when your springs are too soft, and the camshaft actually "throws" the pushrods. Since the springs don't have enough "umpf" to get the valves closed when they should be, the pushrods do not stay in contact with the camshaft lobe as said above. It can lead to both intake and exhaust valves open at the same time, allowing unburned gas going straight through the combustion chamber and out the exhaust valve, increasing emissions and efficiency, and obviously performance (as said above).

[turbohead2332]

Re: valve float

From how I understand it, it can be pretty harmful. Not sure what happens though.

[LETZRIDE]

Re: valve float

From how I understand it, it can be pretty harmful. Not sure what happens though.

does anyone know what happens? I was reading this tech article from ZZP

http://www.zzperformance.com/grand_p...les1.php?id=53 thats mainly why Im asking my question...see from what I understand in the article is that if I install 1.8 roller rockers I dont need to change my springs, and that I will actually see better gains from that...am I reading and understanding this correctly...cause this is sounding too good to be true...

[TheGr8Schlotzky]

Re: valve float

It makes sense that the lower spring rate would net better performance. If you raise your redline with the 1.8s, you will hit valve float sooner than if you had stiffer springs, but not necessarily before a reasonable redline. Less spring rate is like having less mass in the valvetrain, therefore allowing it to run with less friction, letting it rev faster and net you better efficiency and power. If the springs aren't necessary, then you're only adding unneeded friction.

[LETZRIDE]

Re: valve float

It makes sense that the lower spring rate would net better performance. If you raise your redline with the 1.8s, you will hit valve float sooner than if you had stiffer springs, but not necessarily before a reasonable redline. Less spring rate is like having less mass in the valvetrain, therefore allowing it to run with less friction, letting it rev faster and net you better efficiency and power. If the springs aren't necessary, then you're only adding unneeded friction.

Ok so I am right then...if I buy 1.8 roller rockers I don't need to change my springs? what do you think I can use as a reasonable shift point, I have an auto so Im thinking it would probably be best to get a dyno tune to know for sure...but just ball parking it...Im using stock shift points right now...and also how would you know when you hit valve float?

[LETZRIDE]

Re: valve float

anyone with how would you know when you hit valve float?

[cam98aro]

Re: valve float

anyone with how would you know when you hit valve float?

backfiring?

your piston hitting a valve