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One Way

valve train components-78 280z

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Just doing some more component replacing, repairing, evaluating on this resurrection project.  The cylinder head checks out good.  Our local automotive machine shop-Bob Rabon-removed and repaired a couple of the snapped off studs I was not able to get out, cleaned the head and just had to lightly touch up the valve seats.  I did not have him check for flatness on the head, but I think I will drop it off to him before I get around to reassembling the cylinder head.  The rest of the components-all intact but rusted up from the many years of bad storage before I purchased the project-have been thoroughly cleaned in the soak tank, and/or the EVAP-O-RUST solution.  So far so good but am concerned about the rocker arms.  They cleaned up very nicely but several of them have some pitting on the small contact lobe.  The large contact lobes look like new on the rocker arms.  Do they need to be replaced or can some delicate resurfacing work do the trick?  The budget does not like the looks of the cost on replacement rocker arms.  $47 each from Nissan and aftermarkets ranging from $9-$21 but those do not appear to have the same hardened lobes of the originals.  Will I definitely need to change the pivot studs if I do new rocker arms?  All of the repair manuals say yes but hoping for a budget helping solution.  The valve springs are soaking right now and I will be measuring them to see if they are still within spec.  Another concern is the rust on the camshaft itself.  I have not yet tackled that ugly component.  Any helpful tips gladly welcomed

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Cams are tough.  Scotchbrite pad, any oil, and some elbow grease.

Before

before.jpg

After

after.jpg

 

For the rockers, put some 600 grit sand paper on a marble/stone cutting board (TJ Macs kitchen area)  then pull and roll the rocker surface towards you. Water or oil on the paper helps.

Pitting in the surface is OK.

 

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Thank you for the encouraging response. The good news is that my cam is not nearly as bad as yours was.  The bad news is that I am not sure my elbow has enough grease.  That clean up process will be quite the tedious task but certainly worth tackling.  My rocker arm concern actually centers on the rocker arm itself, specifically the small contact end lobe at the valve stem contact area.  Several are pitted and all 12 do have a slight wear groove.  Thanks again, John-Lugoff, SC.

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Sit in a chair and watch a movie, put a towel across your lap and start rubbing the cam with a scotch brite.

No need to rush... after a few days of leisurely scrubbing, it will sparkle.

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VALVE SPRING FREE HEIGHT-The specs I found call for 1.968 outer spring and 1.766 inner spring. I am having trouble navigating our computer to get the FSM to display on the screen so those specs may or may not be accurate.  The springs are now all cleaned and am getting exact same measurements on all 12 springs.  1.920 outer-short by .048  1.695 inner-short by .071.  How critical is the free height?  Is the consistency in the measurements a good enough reason to reuse the springs on this budget conscious resurrection.  Thanks for the input.  The parts are all cleaning up nicely as I slowly continue the project in my limited spare time.  Although 2020 has been a tough year for all, we still have plenty to be thankful to the LORD for getting us through so far.  Thanks again, John-Lugoff, SC.

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2 hours ago, One Way said:

 The springs are now all cleaned and am getting exact same measurements on all 12 springs.  1.920 outer-short by .048  1.695 inner-short by .071. 

Here is the spec illustration from the 78 FSM.  The 49.98 converts to 1.9678.  You're saying that all of your springs are equally too short.

Since the springs are compressed at all times I don't think that free height is critical.  It could only affect preload, but would not affect spring rate.  I'd use them if I was on a budget, but that's me.  Not an engine expert.

image.png

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Thanks for the quick response.  Computer dummy that I am always struggles getting the downloaded files viewable and my wonderful wife is not around to help and belittle me.  My trusty Haynes manual had the same specs.  I was encouraged by the consistent measurements but I am no engine expert either but Zed Head has probably forgotten more than I will ever know about these Z cars.  Thanks for the helpful tips as always.  The camshaft cleaning is underway.  Thanks again, John-Lugoff, SC.

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I got curious so browsed around and found this in the inspection area of the chapter.  It says measure length and tension, and says that "out of spec" is if the number is exceeded.  Typical unclear instructions though, they combined both and didn't specify a tolerance.

If you have the Monroe or Honsowetz books I'll bet there's good advice in there.

image.png

Edited by Zed Head

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This resurrection project was supposedly "RAN WHEN PARKED".  The problem was the park.  The paperwork trail looks like it was badly parked for about 15 years.  Almost 100% complete original, no parts missing except for a center cap on one of the wheel covers.  The head gasket looked good, no signs of leakage or blown areas;  All of the valve train was intact but rusty from poor storage.  I am going to assume it did run until parked and the valve train components all look functional.  If and when we get this project running it will not be driven hard so reusing the OEM valve train parts I think will be safe.  The valves are currently in the soak tank to clean off the carbon deposits.  The valve seats have been cut at our local machine shop and I am going to lap in the valves and see what the valve faces look like after a coarse and fine lapping compound procedure.  Our machine shop said the guides measured up fine and looking at the valves, the stems  look very clean. All of the valves came out easily when I disassembled the head.  The camshaft was seized on bearings # 1 & #2 but some BLASTER soaking and gentle persuasion got those freed up.  I will try the budget cylinder head route and do the lapping and assembly myself and continue the cleaning of the camshaft which will take some time.  Who knows what the specified limit may be.  Lots of repair manuals leave you guessing on some specs.  Hopefully they are not super critical limits.  Thanks again for all the helpful input, John-Lugoff, SC.

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Any recommendations on the valve stem seals?  I have been checking on the MAHLE seals.  VITON or POLYACRYLATE?  A bit of a price difference. I am more familiar with the VITON material but not sure if the POLYACRYLATE is worth the few extra dollars.  Thanks again for all the help and encouragement, John-Lugoff, SC.

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