rod bearing replacement advice?

Steven Carter · **Posted:** Sun Oct 09, 2011 8:57 pm

Hey all,

So my 240Z appears to have chewed up a rod bearing, as noted by the loud metallic sound coming from the rear of the block on recent start-up. The car only ran for maybe 20 secs before I shut it down--hopefully the damage isn't too bad. I haven't yet drained the oil looking for metallic debris, but the sound was much louder than valvetrain noises, and is most likely coming from the bottom end. Until now, the engine made very good compression, blew/leaked no oil and made good oil pressure at idle. I have no real reason for a total engine teardown, and was curious as to how involved bearing replacement is. I hear of some people doing it with engine in-car, from below, but I suspect I'll be pulling the engine. Should I plan on pulling the crankshaft? Replacing main bearings and rear main seal?

I suspect bearing replacement is somewhat generic, except for things like torque values and such, so if anyone's willing to share experience and advice I would appreciate it. I'd like to tackle this over the winter as a DIY project (since the car was a DIY restoration ex paint), and there's little to lose as the engine in question is a remanufactured L28, not the original L24 (which sits in the corner awaiting its fate at some future time)

Thanks in advance!

Bernie Baake · **Posted:** Sun Oct 09, 2011 9:35 pm

Steven, I don't know the history of your engine, but I'm guessing it's old, which means the bearing has been disinegrating for quite some time. These particles have traversed your engine hundreds of thousands of times. How can that be it has a filter? Which is bypassed every time the differential pressure across the filter exceeds a predetermind pressure----like every time you start the car. This is the main reason engines that recieve a single bearing replacements seldom last more than a few thousand miles.
To do a lasting job the engine needs to be cleaned and flushed and that includes all the oil galleries.

DickRasmussen · **Posted:** Mon Oct 10, 2011 7:19 am

In addition to what Bernie says, the crank probably needs polishing . . . assuming the nasty noise is in the engine and not, say, the clutch/TO bearing.

I have no idea why one rod bearing would "go bad" all of a sudden assuming you didn't do something drastic that hurt it last time you ran the car. Z engines are TOUGH. Clutch area stuff would be my first guess/HOPE.

Dick
Former 260Z owner

Steven Carter · **Posted:** Mon Oct 10, 2011 8:34 am

Clutch is nearly brand new, noise comes from the block. I would be surprised if it was the pilot bushing, but honestly i didn't replace that at the time I redid the clutch. The noise is *not*, however, a mild chirping sound that is more typical of a pilot bushing. I am concerned also about potential crank scoring, so the more I think about it the more I have to get comfortable removing the crankshaft. The problem is that I don't want to have to remove the crank since it most likely means removing the pistons, which means new rings and re-honing the cylinder bores--both tasks I didn't want to have to do since the engine made such good compression and blew no smoke.

Sigh. The icing on the cake is that this is likely my own fault, since it occurred about 50 miles after an oil change. I had always used FSM recommendations of 20w50 or 10w40, but this time, obviously, was different even though I used the same oil I always used. :thumbsdown:

First task will be draining the oil looking for metallic debris on the plug, then removing the oilpan to assess for larger shards of nastiness....

JamesShort · **Posted:** Mon Oct 10, 2011 9:34 am

Was it a remanufactured short block or something or did you or a shop build the bottom end?

Steven Carter · **Posted:** Mon Oct 10, 2011 9:58 am

It was a Nissan remanufactured block, brought into service in 2002, bought by me used in late 2005. It had seen some track time, so there was some risk involved, but I bought it while it was still in the car and got to check compression and see/hear it run before I bought it. Paid only $500 for it, including the $300 lightweight flywheel, so I figured it was worth the risk seeing as my OE numbers-matching engine was tired and neede a full rebuild anyway.

JamesShort · **Posted:** Mon Oct 10, 2011 10:02 am

Oh ok, for some reason I thought that engine was a fresh rebuild and/or new.

I know those crazy s54 guys do rod bearings with the engine in the car and just the oil pan dropped. You can try that, but in the event the rod journal is chewed up then you have to pull the engine.

Steven Carter · **Posted:** Mon Oct 10, 2011 10:34 am

yup. That's going to be my process...drop the pan, look for metallic debris, unbolt rod caps and check for scoring on the rods and crankshaft. If none, consider bearings only +/- engine removal for better access. At least in the Z's engine bay there's a ton of space so I can get to it a little better than the way BMW I6's are situated--with those there's very little room to maneuver under there based on how the front crossmember sits so close to the oil pan. In the Z, I can raise the engine 2ish inches before it hits the trans tunnel, and if need be I can drop the front suspension and crossmember in its entirety for better access.

In planning for a potential full rebuild, is T. Hoff still the go-to machine shop source?

BretLuter · **Posted:** Mon Oct 10, 2011 12:17 pm

I don't know about z-car engines but I can't think of any reason you would *need* to pull the pistons out of the bores in order to remove the crank. You would need to pull the engine to get the crank out, but once you flip it upside-down and remove the rod and main bearing caps, as well as the front timing cover/crank pulley, and the rear main seal housing, the crank should lift out.

And, even if you did have to remove the pistons from their bores, there's no reason you couldn't carefully re-install them in the same bores and not have any problems.

For machine shop work, I would recommend CHS- Cylinder Head Specialties in Wake Forest. Despite their name, they are a full service machine shop (i.e.- not just cylinder heads) and they know what they are doing. I don't have any first hand experience with T-Hoff's machine shop in the last 10 years or so, but I've heard that the guys at CHS used to work at T-Hoff before they opened up CHS.

Steven Carter · **Posted:** Mon Oct 10, 2011 12:52 pm

Thanks, Bret. The engine is a pretty standard single OHC non-crossflow design 6 cylinder, not too dissimilar to BMW (except for head design obviously). My chief concern would be re-assembly, particularly given how crank and cam would be separated and the inherent risk of putting things back together mis-timed. I'm pretty good with pics, drawings and notes, and do a fair amount of external orientation marking to ensure proper installation-- but the less that *requires* disassembly, the better off I'll be...

Thanks for the CHS reminder--I'd forgotten about them. THoff also has a partner in Durham called Handcrafted Racing...anyone heard anything about them?

http://handcraftedracing.com/index.html

jeremy gast · **Posted:** Mon Oct 10, 2011 12:59 pm

From what i was told, Mobile Automotive Machining, T-hoff, and the handcrafted guy joined forces about 2.5-3 years ago. I know one of the guys that worked there Joel has done lots of work for some guys in Durham but was told that he is no longer there. I would go with Brett and stay with CHS on capital blvd Wake forest (they built my ex-buddies round track motors for as long as i was crewing for him 93-01)

DickRasmussen · **Posted:** Mon Oct 10, 2011 1:21 pm

Steven,

I helped a friend rebuild his L16 and L24 Datsun engines in the mid 70's. I also replaced the head gasket on my L26. It isn't too hard to get the cam shaft timed properly, especially with the front cover off. I still have the shop manual and the Haynes manual (I think) for my L26 and the plastic tool needed to keep the cam chain tensioner plunger in its bore when just removing the head. My ring compressor may also be the correct size (I only used in on our Lotus 1600's).

Dick
Who hasn't rebuilt an engine since about 1994 or 95.

Steven Carter · **Posted:** Mon Oct 10, 2011 1:40 pm

Jeremy,

Got any leads on an early 80s Nissan Maxima Diesel crankshaft? Just curious....

jeremy gast · **Posted:** Mon Oct 10, 2011 1:47 pm

Choice auto in cary??? They used to be big customer of ours when i worked at Carquest machine shop. 233-0033

Stephen Westerfield · **Posted:** Mon Oct 10, 2011 3:03 pm

jeremy gast wrote:

Choice auto in cary??? They used to be big customer of ours when i worked at Carquest machine shop. 233-0033

Woody's one heck of a nice guy too. I worked for Choice for 2-3 years back in college. He's actually located in the K-mart garage off of Western Blvd now.

THSCC Forums

rod bearing replacement advice?

Who is online