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.

Al_S14 · 10-30-2005, 08:15 AM

piston slap is when there is excesive clearance around the piston ... as if piston is too small for the bore so it is slaping sides of the cylinder wall and not the head. this is common on some turbocharged engines(not factory) whose pistons make noise untill engine warms up and pistons expand.

i think you started your diagnostic process from end. shoudl have pulled the pan and checked rod bearings which is what the problem is. i have yet to see a KA which has stretched the studs enough to spin a bearing or stretch a rod(well this i never hear of period) - its almost impossible.I am certain its rod bearings that took a shit on you from from lots of miles or lack of oil.

Kinematics · 10-30-2005, 09:19 AM

Quote:

Originally Posted by Al_S14

piston slap is when there is excesive clearance around the piston ... as if piston is too small for the bore so it is slaping sides of the cylinder wall and not the head. this is common on some turbocharged engines(not factory) whose pistons make noise untill engine warms up and pistons expand.

i think you started your diagnostic process from end. shoudl have pulled the pan and checked rod bearings which is what the problem is. i have yet to see a KA which has stretched the studs enough to spin a bearing or stretch a rod(well this i never hear of period) - its almost impossible.I am certain its rod bearings that took a shit on you from from lots of miles or lack of oil.

Thanks for the advice. This is just a spare motor for me as I am swapping in a fresh one. I can't pull the entire thing out yet, so I'm just pulling it piece by piece for now.

I'll have to see what the rod bearings look like when I get that far, but thanks.

ledzeppelin240 · 10-31-2005, 10:14 PM

Check the cylinders for out of round and if they are there was most likely piston slap in the cylinder. Check the piston for a collapsed skirt, which would cause piston slap as well as excessive clearance.

The absence of carbon or washed effect is from a coolant leak into that cylinder.

Check to see if the rod bearings have even load wear, also if you have a micrometer check to see if the rod journals and rods are out of round, or elongated.

Kinematics · 11-07-2005, 09:45 AM

I've got the motor pulled out and halfway torn apart, I have to wait on a crank pulley puller to get the rest out, but at least I know now what the issue is with the motor.

Lots of metal shavings. Rod #1 has about 3-4mm of play to it on the crank.

Here's the main piece I've found so far. Looks like rod bearing to me.

I'll probably add a few more pictures once I get the oil pump off and the rest of the assembly removed. Thanks for reading.

10-31-2005, 10:14 PM	#4
ledzeppelin240 Zilvia Addict Join Date: Sep 2003 Location: Sinse Posts: 688 Trader Rating: (0) Feedback Score: 0 reviews	Check the cylinders for out of round and if they are there was most likely piston slap in the cylinder. Check the piston for a collapsed skirt, which would cause piston slap as well as excessive clearance. The absence of carbon or washed effect is from a coolant leak into that cylinder. Check to see if the rod bearings have even load wear, also if you have a micrometer check to see if the rod journals and rods are out of round, or elongated. __________________ Anyway, no drug, not even alcohol, causes the fundamental ills of society. If we're looking for the source of our troubles, we shouldn't test people for drugs, we should test them for stupidity, ignorance, greed and love of power. Looking for: JDM S13 OEM Sideskirts

11-07-2005, 09:45 AM	#5
Kinematics Leaky Injector Join Date: Sep 2005 Location: Westminster, Colorado Posts: 99 Trader Rating: (0) Feedback Score: 0 reviews	I've got the motor pulled out and halfway torn apart, I have to wait on a crank pulley puller to get the rest out, but at least I know now what the issue is with the motor. Lots of metal shavings. Rod #1 has about 3-4mm of play to it on the crank. Here's the main piece I've found so far. Looks like rod bearing to me. I'll probably add a few more pictures once I get the oil pump off and the rest of the assembly removed. Thanks for reading. __________________ image exceeds forum limits -Moderation

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..

10-30-2005, 08:15 AM	#2
Al_S14 BANNED Join Date: Jan 2005 Location: Chesapeake VA Age: 40 Posts: 405 Trader Rating: (0) Feedback Score: 0 reviews	piston slap is when there is excesive clearance around the piston ... as if piston is too small for the bore so it is slaping sides of the cylinder wall and not the head. this is common on some turbocharged engines(not factory) whose pistons make noise untill engine warms up and pistons expand. i think you started your diagnostic process from end. shoudl have pulled the pan and checked rod bearings which is what the problem is. i have yet to see a KA which has stretched the studs enough to spin a bearing or stretch a rod(well this i never hear of period) - its almost impossible.I am certain its rod bearings that took a shit on you from from lots of miles or lack of oil.