L28 from 82 ZX teardown

[Captain Obvious]

Cool! Standard size stock pistons!

I can make out the P79 on piston #6, along with the 34 marking (large "3" and smaller "4") to indicate stock bin sizing. I'm assuming that if #6 is stock, then the rest of them are as well. There should be a "3" stamped into the top surface of the block next to that piston. I can't make that out because it's hidden under head gasket residue. Clean all the pistons up and clean off the block deck and you should be able to see all the numbers.

Nothing else really catches my eye, Looks like a completely appropriate amount of carbon for a used ZX motor. Should clean up well.

I'll measure the thickness of my head and you can do that same. I'm fairly confident that mine has never been shaved, so you can use that number to check yours too.

I've looked at four head gaskets recently from different origins, and all four had manufacturing markings in the same spot... The rib between piston #1 and the timing chain cavity. Like this:

Take a look at yours and see if you can find any marks. If it's aftermarket, it'll tell you that someone had been in there before.

[Captain Obvious]

Non-unretouched photograph:

[Av8ferg]

Captain, cant believe you were able to see those numbers on the piston head.   I cleaned up a piston and now its clear.  So, I’m sill not sure if this engine has been rebuilt.  Can’t find compelling evidence except that the head gasket doesn't have Nissan written anywhere on it.  The only other evidence I might have found is the cam sprocket.  My 77 engine with the N47 head has a different looking sprocket.  It has 3 holes vs the one on the 82 P79 engine which has 8 holes.  Now, when I look for replacement timing chain kits online they all seem to have 8 hole sprockets.  So the question is, is this an aftermarket sprocket and does the stock Nissan sprocket have three holes. See below pics.  

Chain kits see to run from $97 to $150.  Is there any specific brand I’m looking for?   I also need to find a replacement harmonic balance and oil pan.  I could probably salvage mine but this is not how I roll.  I like to do it right the fist time and don’t want to put beat up parts on a rebuilt engine.  Replacements aren't cheap.  $190 for and oil pan and >$200 for a harmonic balancer.   If anyone has some good ones sitting in their garage or barn they want to sell let me know,  

Tomorrow, I’m pulling the pistons and crank out....probably not required I know but down  the rabbit hole I go and I hope you can help me when I try to climb back out,  

A note: my goal is to keep this build around $1000.  This includes the engine cost so I have $600 more to go before I need to make compromises.  Anyway see my pics below. 

     

 

[siteunseen]

22 hours ago, Captain Obvious said:

Non-unretouched photograph:

I could make those dished pistons with my laptop.

You'd do well in politics...

Non-unretouched covfefe.

Edited September 20, 2019 by siteunseen

[Captain Obvious]

3 hours ago, Av8ferg said:

Captain, cant believe you were able to see those numbers on the piston head.

is this an aftermarket sprocket and does the stock Nissan sprocket have three holes.

Tomorrow, I’m pulling the pistons and crank out....probably not required I know but down  the rabbit hole I go and I hope you can help me when I try to climb back out,  

Haha! I've got calibrated eyeballs. That, and it's easier to spot it when you know what you're looking for.

The 82 cam gear looks stock to me. Looks just like the three ZX pulley's I've messed with in recent past. They went to the eight hole version some time between 77 and 81. They also changed if from a sand casting to an investment casting (not that anyone really needs to know that), which accounts for the change in surface texture.

Now, as for your 77 cam gear, I'm not sure. My 77 gear has four holes, so it's different than yours. But dies wear out, so it's completely conceivable that yours is stock, just from a previous die revision. They're always trying to cut weight, waste, and cost. Some (most?) of the aftermarket gears don't have the little timing mark gash on the rear. So by virtue that it's got the timing gash, I'd vote for stock.

My non-expert tips on pulling the pistons out... Pistons come out the top (just sayin'). And make sure you carb cleaner the carbon ring at the tops of the cylinders completely clean first. Don't want to push the rings over that hump. Don't use anything abrasive on the cylinder walls (don't use sandpaper to remove the carbon ring). Push the pistons out slow and evenly. I have seen a few very rare occasions where a piston ring will break when it snaps out of the bore. So if that happens, don't freak.

Did you find the block numbers? Here's a pic of one of my ZX pistons and the corresponding stamp on the block.

Piston:

And the stamp on the block. Left side right next to each cylinder bore. All my pistons were #2 and all my block stamps were 2 as well:

[Captain Obvious]

1 hour ago, siteunseen said:

You'd do well in politics...

Not a chance. I wouldn't do well at all. The only position I would be even remotely fit to fill would be grabbing them by the covfefe.

[siteunseen]

You have my vote! 

SWMBO has my vote.

 

[Zed Head]

Your engine is looking more and more like just a high miles engine.  That glued on badge is an odd thing now.

Aftermarket sprockets only have to match the tooth pattern and shape.  They're not rebuilt like alternators, they are brand-new parts, but made from the aftermarket manufacturers' tooling.  Look for a good brand name.  Cloyes seems to be well known in timing sprockets and chains.  Often you'll find the same exact part for different prices from different suppliers.  Sometimes there's only one company making a part so you might as well just buy the cheapest, unless there's a warranty.

[Captain Obvious]

I'll dig up some pics of the aftermarket sprockets. My suggestion is to get one that DOES have the timing mark gash on it. If it doesn't have the timing marks on it, the only way you'll be able to verify your valve timing would be to use an indicator to degree the cam.

And nobody wants to do that.    

[Captain Obvious]

I grabbed a couple quick pics off ebay... Here's the back of a Beck Arnley aftermarket pulley. See the three timing mark gashes cast into the back side:

And here's the back side of a Federal Mogul Sealed Power. Note that there are no timing marks, so you'd be assuming the timing is where you want it:

Some of the aftermarket stuff has the timing marks and some do not.

[Captain Obvious]

Oh, and forgot to tell you before... The prevalent info on the web says that the original thickness of the Z heads is 108mm, and I've verified that's what mine measures.

I measured the overall thickness of my P79 and it's 4.255 inches (108mm) thick, so my head has never been shaved.

If you check yours and get the same number, it'll be another data point to indicate that your motor had never been open before.

[Av8ferg]

Thanks for the tips. Pistons are coming out nicely after cleaning the cylinders ridges with brake cleaner.
Got my Machine Shop quotes today.

$50 Hot Tank and inspection
$65 Re-honing
$65 clean and inspect the head.
7 day turnaround


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