Valve float?

Fordcowboy · May 2, 2012

I know what valve float is, but have never heard or seen a truck when it happens, so I'm wondering what goes on that you know it's valve float? Flutter in the gauge, noises etc?

A couple times I've had some loud, quick backfire type sounds going on. Only when racing, floored, at the top of the gear. I'm always paying attention to something else when it happens, so I don't know where any of my gauges are at the time. It sounds and feels like hitting a rev limiter, just kind of flat lines on power, and a few quick pop's before it shifts. So I don't know if I am hitting the limiter, or getting valve float. Without valve springs, it's a possibility, but nothing has broken yet, everything is perfectly normal afterwards.

dzldoctor · May 2, 2012

Thats is what valve float sounds like, usually accompanied with valve to piston contact.

Fordcowboy · May 2, 2012

Kinda what I thought, and that I just haven't gotten enough valve to piston contact to break anything yet.

Viking · May 2, 2012

This is why I don't do anymore WOT pulls. I need a new valvetrain in order to do this haha.

woodduck97 · May 2, 2012

If it is before it shifts it may just need the shift point changed. Mine did it before and after I did valve springs. Got the tune changed and good to go. Right as I shift down does it sound something like that?
http://www.youtube.com/watch?v=8rBzxpsCays&feature=plcp

Fordcowboy · May 3, 2012

My speakers suck, so it's kind of hard to tell, but seems like what I heard in your video was quieter and smoother/quicker that what I have, could be the speakers though.

This is what first came to my mind when I heard my truck do it and sounds very similar.
http://www.youtube.com/watch?v=fmNKKox2820

golfer · May 8, 2012

Fordcowboy said:
I know what valve float is, but have never heard or seen a truck when it happens, so I'm wondering what goes on that you know it's valve float? Flutter in the gauge, noises etc?

A couple times I've had some loud, quick backfire type sounds going on. Only when racing, floored, at the top of the gear. I'm always paying attention to something else when it happens, so I don't know where any of my gauges are at the time. It sounds and feels like hitting a rev limiter, just kind of flat lines on power, and a few quick pop's before it shifts. So I don't know if I am hitting the limiter, or getting valve float. Without valve springs, it's a possibility, but nothing has broken yet, everything is perfectly normal afterwards.

the popping at high rpm hasn't anything to do with valve float...that is from tuning...and the video of the import is also purely tuning...those turbo cars will have the spark timing very retarded to light off the fuel mixture IN the exhaust manifold to spool the turbo

Too much injector pulsewidth at high rpm causes the FDCS signals to overlap, and the PCM will cut PW (to 0.6ms on every other signal) to prevent signal overlap.

symptoms of valve float are: loss of boost, loss of power & piston to valve contact (usually resulting in broken rocker arms &/or bent pushrods)

our valves typically don't float from "rpm"...but are more likely to float from boost/drive pressure exceeding the seat load of the valve.

The back of the valve is approx 1.5-1.6"...so if you were running 60psi of boost for example...you'd have 113 "pounds" trying to open the valve, with no aid from the rocker/cam.

the factory specs are 71-79lbs of seat pressure @ 1.833" installed height, for both I&E valves...so the factory valves will try to open (with no consideration to rpm) with just under 40psi of boost.

the higher the boost...the more seat load you'll need to prevent float...but it's calculable, for the most part. boost multiplied by 1.88 should give you a ballpark seat load...

HEUI trucks shouldn't have to worry about the rpm side of things.

Worstenemy453 · May 8, 2012

woodduck97 said:
If it is before it shifts it may just need the shift point changed. Mine did it before and after I did valve springs. Got the tune changed and good to go. Right as I shift down does it sound something like that?
http://www.youtube.com/watch?v=8rBzxpsCays&feature=plcp

I swear on my life that most of your videos have someones phone vibrating in them LOL

woodduck97 · May 8, 2012

Worstenemy453 said:
I swear on my life that most of your videos have someones phone vibrating in them LOL

Well I cant take a video while driving the truck so parkinsons Sean has too.

Fordcowboy · May 8, 2012

golfer said:
the popping at high rpm hasn't anything to do with valve float...that is from tuning...and the video of the import is also purely tuning...those turbo cars will have the spark timing very retarded to light off the fuel mixture IN the exhaust manifold to spool the turbo

Too much injector pulsewidth at high rpm causes the FDCS signals to overlap, and the PCM will cut PW (to 0.6ms on every other signal) to prevent signal overlap.

symptoms of valve float are: loss of boost, loss of power & piston to valve contact (usually resulting in broken rocker arms &/or bent pushrods)

our valves typically don't float from "rpm"...but are more likely to float from boost/drive pressure exceeding the seat load of the valve.

The back of the valve is approx 1.5-1.6"...so if you were running 60psi of boost for example...you'd have 113 "pounds" trying to open the valve, with no aid from the rocker/cam.

the factory specs are 71-79lbs of seat pressure @ 1.833" installed height, for both I&E valves...so the factory valves will try to open (with no consideration to rpm) with just under 40psi of boost.

the higher the boost...the more seat load you'll need to prevent float...but it's calculable, for the most part. boost multiplied by 1.88 should give you a ballpark seat load...

HEUI trucks shouldn't have to worry about the rpm side of things.

Good info. I was leaning more towards this as opposed to valve float, because I think it only happens in one tune. The only reason I was possibly thinking valve float is because at the high RPMS I was experiencing it, is also when my boost is the highest, which still is under 35lbs on my gauge. But thought that maybe stock springs with 300k on them might be a little weaker. But having the valve covers off recently and not noticing anything odd with rockers or anything I figured nothing bad had happened. But all of that is good to know and should be an easy fix with some tuning adjustment.

woodduck97 · May 8, 2012

Fordcowboy said:
Good info. I was leaning more towards this as opposed to valve float, because I think it only happens in one tune. The only reason I was possibly thinking valve float is because at the high RPMS I was experiencing it, is also when my boost is the highest, which still is under 35lbs on my gauge. But thought that maybe stock springs with 300k on them might be a little weaker. But having the valve covers off recently and not noticing anything odd with rockers or anything I figured nothing bad had happened. But all of that is good to know and should be an easy fix with some tuning adjustment.

Quick question who tunes the truck?