After a winter of putting on new Webers, complete rear end refab, balanced driveshaft, etc, etc, etc, I went out tonight for my first test drive since the dyno...I just put new larger 32mm venturi in the Webers.

Ran great up onto I91, went and got some gas, did a redline in the 1st three gear, no problems, felt strong and balanced. Coming up to a stop sign on the way home I heard some tapping under the car. Sounded like my exhaust vibrating against the trans...which I fixed last month. Went away at speed but came back at each stop sign. Started to get a bit scarier and louder but I made it into the garage in the nick of time.

Cam looks fine, exhaust not rubbing, plugs look good. It was when I started it up with the hood open that I realized what the sound is: loose connecting rod(!!!). Its a loud knocking/clacking 3/4 the way down the block inside the wall, no mistaking it.

I'm going to have to pull the oil pan to check it out. Cry for me....

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed

Oh NOOOO!!! Are you sure it's a rod, not a wrist pin? (Double tap at a float, rather than the "little man with the lead hammer" down by the pan at an idle). Borrow my stethoscope and listen at the dipstick hole. I'm leaving in a few hours and will be gone all weekend. Should I bring it to you before I leave?

Frank

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1970 240Z

Thanks but its beyond the stethoscope stage and into the 'look and see stage.'
I don't want to start it again and cause any more damage.

My friend Jim Beam is helping me think things through, I'll do some closer inspecting tomorrow.

-Bryan

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed

Bryan is right, if it's at this stage it's best not to start the engine again, and to pull the pan and check the rods. Only costs a few hours of pain and about $50, if you include the price of a new gasket and oil.

One thing that I do suggest first, however, is checking the crank pulley bolt if you didn't before. When my bolt untorqued itself last year, the sound of the damper wobbling and destroying the woodruff key and crank snout sounded very similar to a loose rod, just harder to pinpoint since it was the last thing I thought of. I eventually discovered it when I noticed my timing marks jumping around under the strobe. I grabbed the pulley and it wobbled back and forth one timing mark.

"The other night I lay sleeping
And I woke from a terrible dream
So I called up my pal Jack Daniel's
And his partner Jimmy Beam..."

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-Chris

This morning...compression is 200psi across all cylinders, so I think the piston lands/rings are ok, no interference or noise while the engine was spinning over which was good.

No knowing more until the pan is pulled

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed

I just pulled the oil pan which incidentally came out easily without having to lift the engine a bit.

All the ARP rod bolt nuts were tight, but I found the #5 rod end would clack slightly when I pushed/pulled it. I pulled off the cap and it looks like I either had some oil starvation or simply some high RPM damage to the bearing. The crank journal appears ok and unscratched, it wasn't spun, nothing appears to have overheated. From the photo you can see there is some scuffing around the oil hole on the left bearing. Very odd is the line across the right bearing. OPINIONS?

I built this engine in 2007 and it doesn't have that much time or abuse on it other than fun street and a few autocross/drag events. It's running so well with such good compression I hate to pull it apart to rebuild...but I'm a little worried that I have a blockage in one of the oil galleys. So much for summer driving this year.

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed

That's spooky. I've never seen a bearing score laterally like that, except when the engine has sat un-turned for years ~ and that doesn't apply to yours.

Frank

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1970 240Z

Is there any possibility it came like that right out of manufacture
and went unnoticed till now?-- without something (like oil) to
highlight that lateral groove, it could have been there all the time.
~Rick~

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All Z Best,.......Kathy & Rick

1969 Z.CAR (#00013 10/69) 8/30/76
1969 ITSA.Z (#00171 11/69) 8/24/73
1970 OLD.Z (#06289 6/70) original owner
1971 510 2dr since 12/31/75
1969 1600 rdstr (our 160-Z)
1971 (#19851 1/71) sold
1975 75.Z (#01343 1/75)

By the way ~ did you find anything gritty or magnetic in your oil?

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1970 240Z

It sounds like a minor oil starvation hit you on the redline. Just a good thought. So get another bearing, plastic gage it, if looks good put it in and look at oil pressure. I would hook up a oil press gauge, not look at the dash. Bearing clearance can affect oil press. Thats why my truck has about 5-6 washers added to the press. spring in the oil pump. The 240 has 2. You will be driving it this summer May the Z be with you.

PS. also would make sense if #5 is last on the oil circuit. Also, my truck is living proof you can just throw new rod bearings in a Nissan and good to go. All 4 cylinders knocked after 3 grand when I first bought it. NAPA had a set for $20. Many miles, and trips later, a few cars towed, and lots of scrap hauled....Tiny Tim lives on.

Thanks Paul, I've been thinking along those lines too. I did a bunch of reading and spoke to the Z Doctor in Roanoke and the conclusion seems to be that if the rod didn't spin that it was likely due to high revving paired with mild oil starvation. That...along with the bearings #5 and 6 being the farthest away from the oil pump means that they got affected first.

I have a turbo oil pump off an auto trans 280ZX turbo on my engine which interestingly is labeled an H3 instead of the H4. The internal parts appear identical to an H4 however. On opening it up the interior was terrible however. It was heavily scored and worn...I suspect that at high revs it was losing pressure. The oil pump came out of an old engine and I had sprayed it out before using but I suspect it was already damaged...yes I should have used a new oil pump...but my current engine oil is clean which is a good sign.

So I plan on slapping in a new set of rod bearings and a new turbo oil pump. Worst case if this doesn't work...time for a rebuild. BTW, many thanks to Chris Colgan who put together an excellent oil pump tutorial/identifier which helped me immensely. http://forums.ctzcc.com/viewtopic.php?t ... t=oil+pump

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed

I'm not Dave, but I'll take the compliment for him.

It almost looks like the pump ingested a piece of the pickup screen. Additionally, you don't have to find a 280zxt auto pump anymore to get the same flow. Apparently the oil pump off the Nissan KA24E (EARLY 240sx w/ SOHC) is the same thing. I think some of the smaller Nissan trucks had KA24DE engines as well. MSA charges something crazy like over $200 for one of those, when you can get a KA24E pump for a fraction of the cost. It needs to be from the SOHC engine because when they changed the head to DOHC the oil pump became incorporated in the timing cover.

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-Chris

My apologies Chris, it was YOUR excellent breakdown...I was confused as usual...now corrected.

I think the pump's damage occurred in the turbo engine the pump came off of, whatever caused the dings don't seem to be in my motor (hopefully). BTW, my rod journal is as smooth a mirror...just like when it came from the machine shop 5 years ago. So the scuffed bearing doesn't seem to have affected it.

Interesting find on the 240sx pump...Rockauto has is as BECK/ARNLEY Part # 0280352 for $70.

http://www.rockauto.com/catalog/moreinfo.php?pk=475661

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed

Well fellas , I found the real cause of the engine knock. If you read the earlier posts you see I blamed the wear on my rod bearings and worn out oil pump.

Well...I replaced the #5 and 6 rod bearings from under the car which definitely removed some of the free play from the rods. But when I rotated the engine using a socket wrench on the front pulley I could still head a sharp "knock knock" as the the crank rotated. What was strange was that if I used a remote starter switch to spin the engine the clunk wasn't there. Something didn't make sense.

So...I pulled the starter off and found my flywheel is slightly loose...if I push on the teeth it rotates back and forth against the bolts...some of them must be loose(@#$%) which means I gotta pull the trans again. I'm using a new Centerforce 2 maybe the extra clamping pressure loosened something.

Well...the upside of all this is that I get to replace my rod bearings, oil pan gasket, and oil pump which needed to be done anyway. Whatta year....

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed