Z24i Rod Bearing Sizes

[D21Driver]

Good Evening Everyone,

I have an '89 D21 with the Z24i and it sounds like it has a rod bearing with excessive clearance. The engine has 306k with perfect compression and excellent oil control, this noise is really the only issue that it has. I have read that it is possible to replace a rod bearing with the engine in place so I am wanting to remove the pan and try doing this if it looks like there is enough access.

I called my favorite online Nissan oem parts source this evening and learned that standard size rod bearings come in two sizes. The sizes are listed as 1.502 - 1.506 and 1.508 - 1.512. The factory shop manual calls for a rod bearing clearance of between .0005 and .0021 inches. The bearings aren't terribly expensive so I'm thinking that I order both, inspect and measure the crank journal and then install the bearing that yields the correct clearance.

If anyone has done this while the engine is still in the truck or has advice on rod bearings I would really appreciate hearing from you. Thank you in advance for any knowledge you have to share on this subject.

[seang]

Have you adjusted the valve lash?

[D21Driver]

Thank you for the suggestion Seang. I did adjust the valve lash when I first noticed the noise but it didn't make any difference in the sound so the problem may be elsewhere. If nothing else I'm going to remove the oil pan and just see what each of the rod bearings feels like. At this point I'm mostly curious about the sizing of the "standard" rod bearings and am really hoping that someone can explain this to me.

[seang]

If you measure the clearance of the new bearings on the crank and make sure you install the right ones I don't see how you could make things worse. What gets me is if a bearing is bad, what caused it to go bad? Has it simply worn out, or is there a clogged oil galley, or low oil pressure? But, like I said, at this point I don't see how experimenting with new rod bearings could make things worse for your engine, but that is all I can guarantee with what I know.

About the sizing, from what I know, even factory engines can come with different sizes, so the only way to know is to measure your crank journals.

http://lmgtfy.com/?q=How+to+measure+crank+journals

[D21Driver]

That's a very good point. I bought the truck new, it's always had regular oil and filter changes. I've had the valve cover off and it's clean inside. I switched to Mobil 1 and the Mobil 1 filter at around 200k. I can't prove it but I started out using the oem filters and sometimes I could tell that they would allow oil to drain back into the pan so it's possible that was a contributing factor. Next oil change I am at least going to remove the pan and see what I can find out. I would love to find a parts truck and have a spare engine to rebuild and just swap in. I'll get it sorted out one way or another. Thanks for taking the time to reply, I do appreciate your advice.