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L24 rebuild


BEERDAMAGE

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My lady is the third owner of this 72 240Z.  The engine is tired and I am rebuilding in my "temporary" garage.  (costco 12f/20f frame canoopy)  As I check it out I see that there is rust underneath the caked oil and dirt.  It is WAY overdue for some work.  What I think I'll do it take pictures and notes and chronicle what I'm doing in this thread.   I have rebuilt an L-24 25 years ago, and I have experience with 
Air cooled VW's and Pre 69 American cars.   I'm certain that MURPHY will be lurking over my shoulder.  Here is my progress dismantling the engine todate.  When I have time I will work on it.  The goal is to have it on the road before nextr summers car show season.

 

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I had time to to disassemble some of the engine today.  It is caked with crud!!!  and then there is crud under the crud.  Way over due for some love.  I have ordered gaskets and some specialty parts.  Sent the Distributor to be rebuilt since this is an Automatic, ..,,;;  My lady can only drive them since her workplace accident broke a total of 8 Vertebrae in her neck and lower back...  So here are a few pics of the tear down.  I have about 8 books and two shop manuals but will welcome any and all advice.   Then I'll do what I want~~ 

 I'm certain there will be lots and lots of cleaning and gasket scraping.  I see where some previous work has been perf'ormed and high temp silicone was used for gaskets.  I ordered gaskets and will use COPPER COAT gasket sealer.  It has worked very well for me in past rebuilds.

  Here is the Spark plugs layed out in order.  They tell a lot of this engines story before the rebuild.

 

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The engine hang ons have all been removed.  Rusted bolts are snapping like fireworks.  I have been very busy removing them.  I will also be scraping all the crud off with a putty knife.  Talked on the phone to Rock Auto about carburetor rebuild kits.  The guy says, "There's no difference between the front and rear carburetor, one kit fits all".  No, sorry, that's entirely wrong.  Similar like mirrors. Ordered it from zparts where the guy says, Yes they are different rebuilt kits. Similar yet different.  Ready to remove the head.

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Gaskets do not require coatings, at all, even the head gasket. Nissan didn't use them and really, that's the job of the gasket to seal between parts anyway. Silicon oozing out from between parts is a dead give away that the builder doesn't know any better.

 

If you are not removing the timing cover and timing chain be sure to block the tensioner from falling out before removing the cam sprocket... or it will fall out and you will be removing them to fix it.

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Taking off the front cover, water pump.   Nasty!  I just love the silicone goo,  I'll have to make sure none of it has blocked passages.

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This sure looks pretty.

 

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A New Toy

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some more parts removed, bagged and tagged.  I have taken HUNDREDS of pictures and are only posting a few.  The pictures are of course, to show me what I did and put it back together with minimal hair loss.

 

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Oil pan removed.

 

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  I plan to replace the timing chain and possibly the sprockets.   I'll check with my machinist concerning their condition.  He'll probably recommend new parts all around, tensioner, guides, sprockets.  I will also be putting in new bearings in the bottom end.  This is where I am today.  Like all of us my available working time is limited.  I'll buckle down when I can to get this Z on the road. 

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Probably, this crap is everywhere.   I'll have to do my best to clean every passage I can!  Won't be doing much for the next three weeks, the Z owner tells me we are taking a cruise.  Meanwhile back at the ranch the Head has been removed. 

 

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This is as nasty as it looks.

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The piston faces tell a story.

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This is sweet.  This L-26 is going to be loving the repair.

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Yes she did use it as a "limited" driver, sometimes.  She has owned this for a while, I'm not allowed to work on it until now. NO problems, please don't read anything into that... She asked for help when it ultimately died.  I did tell her that it was a very poor rebuild to start with and it needed help LONG before it quit.   She didn't drive it much however, probably a total of 3,000 miles.  The compression test showed  from 35 to 180 lbs. in the various cylinders. a squirt of oil solved most of the poblems so there most likely is some valve guide problems.  Part of the plan is to install new guides.  If They are THE problem or part of the problem, it will be repaired.  The Pistons, connecting rods,  and cylinder walls appear to be in good shape.  I have ordered Crank and connecting rod bearings. I also ordered moly rings for the pistons. Rebuild top and bottom Gasket set and carburetor rebuilt kits.   I have Claimed the front porch for tools and cleaning parts.  I really don't want to be interrupted by a cruise, but I will probably think of other projects to do on this later.  "SHE" has decided she needs my help.  This is after of course I built my 1951 KAISER Manhatten Dragon....

  Next I will remove the pistons, then strip the head of everything except the towers. 

 

Okay, it's not a Datsun but this car led to the opportunity to play with the 240.

 

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35? Did you try setting the valve lash first to see if that would improve the compression? Maybe tight valve(s) on that cylinder.

 

Adding oil will only up the compression if it's the rings that are leaking. Valve guides won't affect compression. Bad valve seats will though.

 

Never use chrome rings unless you have a shop over bore the cylinders. Used/worn cylinders are not perfectly round enough for chrome rings. They will wear the honed surface  out before they can wear the cylinder round and seal. For a quick hone and ring job, use softer cast iron. 

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thank you for the help.  Yes, the valve lash was set while warm with the compression spread over a wide range.  Squirting the oil in helped me discern the rings as the most likely culprit and since there was still a smaller compression difference, acceptable with all cylinders 165-180.  The valve guides still could be a small issue.  I found a Molymbdenmum ring set that is suppose to seat quickly like iron and have better lubrication qualities

.  I used chrome once on a VW rebuild with dubious results.  It was a pain as the rings never did seat correctly and I replaced them with iron.  

  So after I serviced the Chrysler, Oil, filters, flush and fill new coolant/antifreeze I had a little time to work on the Z.  Every little bit helps.

12022371_992616394113904_719212359382951  This is nasty and will receive a good cleaning.  The sprocket and Oil thrower look fine.

 

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Removing the pistons and connecting Rods.   They look okay, covered with varnish.   Every book and my memory have cautioned me NOT to mix up parts and location or overlook orientation.   Everything will be marked, bagged and tagged.  My memory is best on paper.

 

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Pistons are out and marked

 

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Gaskets and other goodies delivered by UPS just a bit ago.  Pistons are laid out.  I'll clean them, remove the rings and oiler, then tell her I need a groove cleaning tool just because.  I usually have used a broken ring to clean the grooves but I deserve her to get me a toy.  :)

 

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  • 2 months later...

The Cruise and the Trip were great.  Lasted longer than originally planned.   I have not been able to get back to the car yet as all hell broke loose shortly after we got home.  Since I missed many deadlines and the build is behind original schedule, I will do a few other repairs not on the list yet.Sometime after Christmas I'll be able to get back to it. 

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  • 2 years later...

This has been a long time,  "IT" happens and prevented me from working on the 240.   The Engine is together, yay, and I am attempting to start it BEFORE I install the radiator and the rest of the cooling system.  Yes, don't run it very long and over heat it.  No worries about doing that, just want to get it to fire.  It did and does, but I did not let it run due to a leaking fuel nozzle on the FRONT carburetor.  My service manual was not very helpful as it said, adjust fuel nozzle.  The nozzle is loose and the only thing that holds it in place is the connecting plate.  The needle value is set correctly. Fuel flows FREELY when the engine is turned over.(which sounds great by the way).   Is there are trick or practice that makes the fuel nozzle seat correctly?  Could this be a need to adjust the connecting plate?  Help, knowledge and CONSTRUCTIVE criticism is greatly appreciated.   I hope this post hasn't been buried after 2+ years of  being away. 

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Thank you.  Yes, the over flow was also spewing gas. Removed the carburetor and float bowl.   I discovered that the metal tab on the float was not high enough to close it. I rebuilt the carbs, almost two and a half years ago and the valve was a new part.  I think the travel was different as I used the same float.  Adjusted the metal tab and tested the flow until I have it working, correctly I hope.  Tested the float and it is okay.  Put everything back together and mounted the carburetor.  It is now dark and I don't have enough light to work.   Tomorrow I will give it a test.  

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