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Discussion Starter · #1 ·
I'm rebuilding my first L28 (first engine as well) and recently got my block back from the shop. The cylinders have been freshly bored and I'm installing new pistons with new rings. I'm following the book recommended on here (How to Rebuild your Nissan & Datsun OHC Engine Manual).

I've just compressed and dropped in my first piston and hand tightened the rod on to the crank. When I rotate the crank, on the way up the piston makes very little noise (a slight air squashing noise) but on the way down especially at the bottom of the stroke there is a slightly different sound. It doesn't sound like air compression it sounds like a faint scrape. I removed the piston and checked the bore, there is no scratches or marking and no indication of any issues. I have re gapped my piston rings and ran the gap edge over some 1000 grit sandpaper (although I couldn't see or feel any noticeable bur). When re-installed I can still hear the slight scraping noise, I also tried the second piston and experienced the same. Is this a normal sound? its quite a faint noise but its definitely there.
 

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I recently rebuilt my engine and installed new rings on an L28. I don’t recall hearing this noise BUT at the same time I wasn’t listening for anything either. A couple things I recall being critical was making sure the cylinders as absolutely, perfectly clean...I got a lint free cloth and obsessively cleaned it. Secondly, if I recall the ring has a top and bottom. I think on there was a marking on the ring to make indicate that, make sure that’s correct. How was you ring cap at the top of the stroke? And did you check it at the bottom also? Again I think cylinders can have have minor differences in bore due to wear (like a cone but very minor). Were the cylinders rebored or just honed? It may be possible that the ring is super tight at the bottom of the stroke and the ring gap too small causing the ring to scrape vs slide. Did you apply vey light coat of motor oil to the walls all the way down. How many miles in the engine prior to rebuild? There are guys way more qualified than me to answer this but those were some of my thoughts having just rebuilt an L28 engine last spring.


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Good thoughts in that. Miking the cylinders top and bottom (if they weren't bored out) is important.

Rings have to be installed in specific configurations; there are right side up and upside down possibilities. You also need to stagger the end gaps. If in doubt, I'd pull the pistons while it's convenient and double-check.
 

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Discussion Starter · #4 ·
I recently rebuilt my engine and installed new rings on an L28. I don’t recall hearing this noise BUT at the same time I wasn’t listening for anything either. A couple things I recall being critical was making sure the cylinders as absolutely, perfectly clean...I got a lint free cloth and obsessively cleaned it. Secondly, if I recall the ring has a top and bottom. I think on there was a marking on the ring to make indicate that, make sure that’s correct. How was you ring cap at the top of the stroke? And did you check it at the bottom also? Again I think cylinders can have have minor differences in bore due to wear (like a cone but very minor). Were the cylinders rebored or just honed? It may be possible that the ring is super tight at the bottom of the stroke and the ring gap too small causing the ring to scrape vs slide. Did you apply vey light coat of motor oil to the walls all the way down. How many miles in the engine prior to rebuild? There are guys way more qualified than me to answer this but those were some of my thoughts having just rebuilt an L28 engine last spring.


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I did put the rings in using the top markings to make sure they were facing up. Cylinders were rebored and I did oil the cylinders. Car had 92000 before I started the rebuild.

What is a ring cap? sorry I haven't done this before so I'm a bit unfamiliar with the terms.
 

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That was a typo. I meant to type “ring gap”. You should check the gap in the compression ring. There are max and min tolerances you need to confirm. If the gap is too small you’ll need to remove some material to get it right. I put in OEM Nissan rings and my gaps were fine but I did notice a difference between to upper and lower portion of then cylinder.

Here’s a video I made measuring ring gap.


There are other videos on my channel of my build that might help as well.


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Discussion Starter · #6 ·
That was a typo. I meant to type “ring gap”. You should check the gap in the compression ring. There are max and min tolerances you need to confirm. If the gap is too small you’ll need to remove some material to get it right. I put in OEM Nissan rings and my gaps were fine but I did notice a difference between to upper and lower portion of then cylinder.

Here’s a video I made measuring ring gap.


There are other videos on my channel of my build that might help as well.


Sent from my iPhone using Tapatalk
Ahh yes I did the ring gaps but only at the top of the cylinder. I'll try the bottom now. Thanks
 

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I usually take a cardboard box, go stack all the rings and try each one in one hole to get an idea of their size. Then go down about about 1/2 then full stroke and check each hole for top/mid/bottom difference.

Lay out each ring based on being looser/tighter, so you have a row of 6 top, 6 middle, etc... Then find the combo that is no bigger than spec and error towards having some too tight... Then file the tight ones as needed.

I assume you know about the offsite, upside down (face/back) and maybe a back groove/bevel (goes facing top IIRC).

It takes a bit to custom match if they are much different from each other.

Don't forget the side clearance. Each ring should have a set gap as it sits in it's groove. I think it's very slim and different between 1st and 2nd ring.
 
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