KA Teardown Question (Rod knock/piston slap) - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Kinematics · 10-29-2005, 11:41 PM

I purchased this project car a few weeks ago, with rod knock. I pulled the head today, and everything seems to be in good shape. Though, there is an odd mark on the #1 piston that I can't decipher. The arrow is pointing at it in the picture below.

To clarify, this 'mark' is actually complete absense of any carbon on that section of the piston. It doesn't appear to be scratched or bent or dented in any way. Each cylinder (upon quick visual inspection) is free of any scoring or groves on the cylinder walls.

As you can see all of the pistons are blackened as normal. However, there is that one little section on the #1 piston that is clean. I have suspicion that this was coming in contact with the head, however there are no pertaining marks on the head to confirm this or not. For good measure, here is a picture of the head.

#1 piston is on the far right on the picture. Intake side is on the upper half of the head. Inspecting the head, I don't see any physical damage done to it, though I haven't cleaned it up to take a closer look, or do any measurements to see if the head is warped or otherwise damaged.

The point of this post is, am I wrong in my suspicion that the piston was slapping the head, or is there another possible answer? I won't find out about the condition of the bottom end for at least a few more weeks, but I'm guessing the source of the knocking is from a stretched rod, rod or main bolts.

Thanks for any input.

Edit: Additional note, all the valves seem to be in good alignment, and none are bent.

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10-29-2005, 11:41 PM	#1
Kinematics Leaky Injector Join Date: Sep 2005 Location: Westminster, Colorado Posts: 99 Trader Rating: (0) Feedback Score: 0 reviews	KA24DE Piston Question UPDATED I purchased this project car a few weeks ago, with rod knock. I pulled the head today, and everything seems to be in good shape. Though, there is an odd mark on the #1 piston that I can't decipher. The arrow is pointing at it in the picture below. To clarify, this 'mark' is actually complete absense of any carbon on that section of the piston. It doesn't appear to be scratched or bent or dented in any way. Each cylinder (upon quick visual inspection) is free of any scoring or groves on the cylinder walls. As you can see all of the pistons are blackened as normal. However, there is that one little section on the #1 piston that is clean. I have suspicion that this was coming in contact with the head, however there are no pertaining marks on the head to confirm this or not. For good measure, here is a picture of the head. #1 piston is on the far right on the picture. Intake side is on the upper half of the head. Inspecting the head, I don't see any physical damage done to it, though I haven't cleaned it up to take a closer look, or do any measurements to see if the head is warped or otherwise damaged. The point of this post is, am I wrong in my suspicion that the piston was slapping the head, or is there another possible answer? I won't find out about the condition of the bottom end for at least a few more weeks, but I'm guessing the source of the knocking is from a stretched rod, rod or main bolts. Thanks for any input. Edit: Additional note, all the valves seem to be in good alignment, and none are bent. Last edited by Kinematics; 11-07-2005 at 09:46 AM..