2006 4.8 broke intake valve at keeper groove? has this happened to you?
06-07-2015, 02:50 PM
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2006 4.8 broke intake valve at keeper groove? has this happened to you?
Is this common? Thats my biggest concern. I have a set of 2004 241 heads going on right now.
The stock original heads had double springs installed and I don't know if they are too much for the stock cam to handle.
At the moment, I'm not sure if the truck has an aftermarket cam in it. I will put a dial indicator on it in the near future to measure lobe lift x 1.7 rocker ratio.
The valve broke after my maiden test drive of about an hour with a new low-boost bolt on turbo that actually drives quite nice. No issues while cruising. I had STFT sitting at 14.2 at cruise / ~12.5-13.0 on light accel no boost accel. I have wideband installed and it was reading nicely.
The breakdown occurred right in front of my garage as I was about to stop logging my pids on efilive. I gave it one last rev to 3-4k in Park gear and then Zzzzzzzzzzz-- . turned it off within a few seconds. It sounded like playing cards in the spokes of a bicycle. I cranked it in clear flood to confirm lost compression and it was obvious no compression on one cylinder.
I didn't even try to start it again and pushed it into the shop to begin the teardown. I put a borescope down cylinder #6 spark plug hole and there was the intake valve the sitting there static in motion with the piston still moving. Lucky for me the valve was still in the head and not embedded in the piston. No damage to the piston but there are some obvious marks on the piston crown.
I'm going to take this opportunity to re-ring the pistons with the block still in the car. (Previous owner had an over fueling issues that washed down the cylinders. 10-15% leakage on 3 pistons past the rings because of that mistake. I want my leakdown numbers around 5% with a good ring gap for turbocharged cylinder pressures.
Are the double Valve springs too much pressure for OEM valves? I have to make a choice of what springs to put on my 241 heads.
J
The stock original heads had double springs installed and I don't know if they are too much for the stock cam to handle.
At the moment, I'm not sure if the truck has an aftermarket cam in it. I will put a dial indicator on it in the near future to measure lobe lift x 1.7 rocker ratio.
The valve broke after my maiden test drive of about an hour with a new low-boost bolt on turbo that actually drives quite nice. No issues while cruising. I had STFT sitting at 14.2 at cruise / ~12.5-13.0 on light accel no boost accel. I have wideband installed and it was reading nicely.
The breakdown occurred right in front of my garage as I was about to stop logging my pids on efilive. I gave it one last rev to 3-4k in Park gear and then Zzzzzzzzzzz-- . turned it off within a few seconds. It sounded like playing cards in the spokes of a bicycle. I cranked it in clear flood to confirm lost compression and it was obvious no compression on one cylinder.
I didn't even try to start it again and pushed it into the shop to begin the teardown. I put a borescope down cylinder #6 spark plug hole and there was the intake valve the sitting there static in motion with the piston still moving. Lucky for me the valve was still in the head and not embedded in the piston. No damage to the piston but there are some obvious marks on the piston crown.
I'm going to take this opportunity to re-ring the pistons with the block still in the car. (Previous owner had an over fueling issues that washed down the cylinders. 10-15% leakage on 3 pistons past the rings because of that mistake. I want my leakdown numbers around 5% with a good ring gap for turbocharged cylinder pressures.
Are the double Valve springs too much pressure for OEM valves? I have to make a choice of what springs to put on my 241 heads.
J
06-07-2015, 03:32 PM
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The valve break occurred right at the valve spring keeper retention groove. Oem rockers as well.
Do you think a lean condition can cause a valve to break at that location on an intake? Could the cletus that did the spring install do something to the valve to create a weak spot?
Do you think a lean condition can cause a valve to break at that location on an intake? Could the cletus that did the spring install do something to the valve to create a weak spot?
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