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Discussion Starter #1
So,

I finally got my marine hi-pops. Got 'em installed... and now I have a new noise. I had a real distinct "knock" before, but now I have this rattle at constant throttle. It is high pitched and sounds as if someone were tapping my pistons with a ballpeen hammer. It isn't real prevalent at idle, but comes on with steady cruising, and constant throttle. I noticed it more this afternoon than any previous times. What I am seeing now is the inverse of what was happening before. I used to have the pronounced "knock" at idle, which is gone now. Now I have a considerably smoother idle, with a clatter under light throttle.
Second part of the story... tonight on my way home from an SAE meeting the truck felt considerably more powerful. When under constant throttle there was no rattle. So, what I am tending toward at this point is that the timing is somehow off, producing a slight to moderate advanced condition. However, I have no idea what would have changed this evening to make it all clear up like that. I am familiar with the fact that even OBD-I vehicles have BLM (Block Learned Memory) to some extent, wherein the computer adjusts its fuel and spark curves in the event that there has been a major change in a single component's performance. What doesn't fit here though is the fact that BLM usually takes less than 5 minutes. I have over two hundred miles since the injectors were changed.
Has anyone else had similar experiences? Does anyone know why I have this "clatter"?

As always, I appreciate your comments

Sean
 

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Yup they do knock more especially when cold out and TDC offset is bumped up, also take a look at the turbo heat shield, if it is loose at all it acts as a amplifier for that knock. right after start up while still cool place your hand on the turbo heat shield and see if it dampens the noise.
 

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Discussion Starter #3
So, am I hurting anything? I realize that pre-ignition is bad in anything because of the hammering effect of the forces generated. Is the noise I am hearing actually "pre-ignition"? Can I check TDC offset without a Tech-II? I was pretty liberal with the "reassembly torque"... but I will check the heat shield as you suggest. Thanks Tim.

Sean

Forgot one thing... Why would the noise suddenly go away, and the engine seem more powerful?
 

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ECM finally ran a random diagnostic and reset timing??
 

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Discussion Starter #5
Further Analysis Proves...

Well,
after further analysis, and careful deliberation, I have concluded that I know not what the hell is going on here. My problems don't really seem to be problems at all. When the "clatter" is loud enough to be heard there seems to be plenty of midrange power. Conversly, when the "clatter" is not audible there seems to be an abundance of high end power. So, I have concluded that my timing may be a little too dynamic in the sense that it varies enough to influence power distribution. I guess what all of this nonsense is trying to say is that I suspect a problem with the mechanical side of the IP's timing.

What the hell?

Sean
 

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Keep in mind that the pistons are real prone to cracking and the added stress might be harmful over the long haul.
 
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