Floating valves?
Thread Starter
Teching In
Joined: Feb 2012
Posts: 37
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Floating valves? I have a really odd issue going on and wanted to know if anyone has ever floated valves and lived to tell the story?...lol I feel my engine may be flaoting valves and it has me scratching my head.
This only became a issue since I have swapped my ems to a holley hp efi unit, cam, push rods and valve springs. What is happening is at about 6000 rpm my engine will lay over hard in power (can be felt and heard audibly) and in a data log you will actually see the rpm drop 200 rpm and the boost spike up 2-3 psi for a moment.
With that said I feel the valves are floating and causing a "anti-lag" effect causing the boost to shoot up but power to be lost. Only signs I have found visually is on the drive side of the engine all of the valve stem seals are off of the stems for some weird reason. Passenger side is all good.
I dont think this is a holley coil issue as this is a new box where the issue is suppose to be fixed. Other than the issue at 6k the truck runs great. It pulls like a bear up until that point. I have attached two logs over laid showing its not exactly the same point but roughly 6k every time and always drops rpm and boost shoots up and afr goes a bit lean. (may be going a bit lean due to unburnt oxygen as its not getting to burn it from valves not closing)
Any input or help is welcome.
Lq9 stock bottom end
317 heads
s475 1.32 hot side
dual 44mm gates
15 psi creeping up to 18ish
lots of meth
custom tubular headers
*new parts since issue*
(speed inc cam kit)
Speed inc tu2 cam
Push rods cam with the cam kit (unsure of brand right now)
Brian tooley .660" lift springs
Holley hp efi
This only became a issue since I have swapped my ems to a holley hp efi unit, cam, push rods and valve springs. What is happening is at about 6000 rpm my engine will lay over hard in power (can be felt and heard audibly) and in a data log you will actually see the rpm drop 200 rpm and the boost spike up 2-3 psi for a moment.
With that said I feel the valves are floating and causing a "anti-lag" effect causing the boost to shoot up but power to be lost. Only signs I have found visually is on the drive side of the engine all of the valve stem seals are off of the stems for some weird reason. Passenger side is all good.
I dont think this is a holley coil issue as this is a new box where the issue is suppose to be fixed. Other than the issue at 6k the truck runs great. It pulls like a bear up until that point. I have attached two logs over laid showing its not exactly the same point but roughly 6k every time and always drops rpm and boost shoots up and afr goes a bit lean. (may be going a bit lean due to unburnt oxygen as its not getting to burn it from valves not closing)
Any input or help is welcome.
Lq9 stock bottom end
317 heads
s475 1.32 hot side
dual 44mm gates
15 psi creeping up to 18ish
lots of meth
custom tubular headers
*new parts since issue*
(speed inc cam kit)
Speed inc tu2 cam
Push rods cam with the cam kit (unsure of brand right now)
Brian tooley .660" lift springs
Holley hp efi
Usually, valve float shows as a progressive power loss on curve. Your power curve starts to climb again after the event. So, I'd look @ spark controller &/or engine knock. What are your intake air temps? Log intake air temps & knock. If these are OK, look @ timing controller. Might also be spark blow out. Check your plug gaps.
.030" shims? So, the spring compression was off & you weren't getting the spring force required to keep valves from floating. Must have been the pressure spike that made the graph show power start to climb again after initial loss.
Thread Starter
Teching In
Joined: Feb 2012
Posts: 37
Likes: 0
Just because the rpm goes up did not meant the power went up. That is strictly a data log. The truck was falling on its face hard once the boost came up. 1st and 2nd the truck does about 10 psi and third it does what you see, about 16 once it levels off. The truck went 9.99 at 133 previously, yesterday it went a 9.65 at 141 no tune change.
