L28 from 82 ZX teardown

[Captain Obvious]

I'm no pro, but I'll weigh in anyway and say "Wow". That is definitely in the same league as my busted cam tower alignment. I'm wondering if the last guy tried to press the seat in with the head cold and that's all the farther he could get it in. Gave up and just dug the grinding in extra deep to account for it. That's pretty bad.

So it looks like the thin lip around the edge broke off along the side opposite the companion valve? Is that the case? Sure hoping it broke off during the seat cutting operation and not after the head was put into service!! Any dents on the piston top from pieces getting knocked around in there?

If that's the only issue, your machinist should be able to take care of that pretty easy. If he says the rest of the head is good, then I'd stick with it. If he skims the head clean, you'll be at .010 to .015 (ten to fifteen thousandths) off stock. I don't think any of the other components (like the timing chain) will care about that small of a change.

[ensys]

 

Well, I'm no "Pro" either, but....

Generally speaking, a head is considered flat if it is within a few thousands across opposite corners. Presumably, if he wants to cut .005", the amount of "out" is likely on the order of something between .001 and .003 and he wants, of course, to cut thru it to "flat".

Were it I, keeping in mind that once cut, you can't put it back, and that every cut is another chance for an error that can easily exceed the presumed current amount of "out", I would demure the risk, figuring that torquing it up would pull things right.

Besides, be aware that every head cut complicates something; in this case, the cam timing.

If you must have an increase in the C.R., I would suggest it would be better worked out with pistons for more control.

As for the seat condition, it would seem your machinist has a talent for understatement. While I don't know everything that can happen to a valve seat, that is certainly the most remarkable situation I have ever seen. As I don't believe it's possible for a solid seat to vertically shear off an outer segment against an alloy socket, I cannot help but deduce that some mope has tried to shim a seat into an enlarged/poorly cut pocket. And from the look of things, it seems very possible (even if a "guide-centric" cutter was used on the seat) that the valve that lives there has been hitting the seat off-center since the bodge was perpetrated. Since it would seem he has not noticed as much, I would suggest a second opinion regarding valve/guide wear and square. In any case, this will take some talent to rectify, and you might want to wait for the outcome before making any decisions on other operations.

Ironically, the owner who commissioned this bit of whimsy, probably trusted his machinist to make all the decisions.

$.02 from the peanut gallery.

 

Edited October 18, 2019 by ensys

[Av8ferg]

Thanks for the feedback and opinions. I tend to agree that finding another head doesn’t mean it will be good. The machinist said this is an easy fix.
- Captain: No all the pistons look fine but I’m not done cleaning them either, so that may change.

- ensys: I agree there is always a chance to screw it up more. I live in eastern NC. Access to world class machine shop is not an option. You get the good ol boy machinists here. This place build race engines and they guy has been doing it for 15 years. He’s a good ol boy but no stupid. I think Perfection is the enemy of good. In pursuit of perfection in life can make thinks worse. I’m leaning toward not cutting it at all like your suggested.

So, another controversial topic is Rod Bolts. People seem very polarized on this topic. Car guys ( not Z guys) that are my friends around me all recommend replacing the rod bolts for piece of mind. There are many on this forum and others that say this is totally unnecessary. My thoughts are leaning towards replacing them. Here’s my rationale.
1. I don’t know the engine history. All I know it’s been cracked open before.
2. It’s about 40 years old
3. Only hurts the wallet to replace these bolts
4. Rod bolts take the brunt of the engine force. Why risk it? Spend $60 for piece of mind vs risking $1500 or more after a rod bolt snaps when I’m driving to Pikes Peak like Dave WM.

I’m found a set of ARP for $55. Nissan Stock ones for $46.

Anyone know where to find OEM Nissan Valve Stem Seals. Zcardepot wants $62. Seems outrageous!



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[Patcon]

I come down on the cheap insurance side of the debate on the rod bolts. If the budget allows I go ARP

[Captain Obvious]

About the rod bolts... It seems that you should have the rod big end checked and potentially resized if you change the rod bolts. I had previously discounted this claim, but after seeing @madkaw's engine failure, I give it some credence. After reviewing the geometry, I understand the concern. So add that cost to the list too if you are going with new bolts.

That said... As for me? I'm planning to re-use my old rod bolts. I'm even going to replace one of them that galled when I took it off. Threads are messed up and I'm going to replace just that one. I suspect there was a little metal chip in there when they did the original install at the factory and it smeared a couple threads when I took it off.

[madkaw]

1 hour ago, Av8ferg said:

Thanks for the feedback and opinions. I tend to agree that finding another head doesn’t mean it will be good. The machinist said this is an easy fix.
- Captain: No all the pistons look fine but I’m not done cleaning them either, so that may change.

- ensys: I agree there is always a chance to screw it up more. I live in eastern NC. Access to world class machine shop is not an option. You get the good ol boy machinists here. This place build race engines and they guy has been doing it for 15 years. He’s a good ol boy but no stupid. I think Perfection is the enemy of good. In pursuit of perfection in life can make thinks worse. I’m leaning toward not cutting it at all like your suggested.

So, another controversial topic is Rod Bolts. People seem very polarized on this topic. Car guys ( not Z guys) that are my friends around me all recommend replacing the rod bolts for piece of mind. There are many on this forum and others that say this is totally unnecessary. My thoughts are leaning towards replacing them. Here’s my rationale.
1. I don’t know the engine history. All I know it’s been cracked open before.
2. It’s about 40 years old
3. Only hurts the wallet to replace these bolts
4. Rod bolts take the brunt of the engine force. Why risk it? Spend $60 for piece of mind vs risking $1500 or more after a rod bolt snaps when I’m driving to Pikes Peak like Dave WM.

I’m found a set of ARP for $55. Nissan Stock ones for $46.

Anyone know where to find OEM Nissan Valve Stem Seals. Zcardepot wants $62. Seems outrageous!



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Budget in another 10$ per rod for sizing. You need to resize the rid big ends if replacing with ARP. 

Cutting the head face is a straight forward process. It’s not risky , anymore risky than not resizing rod bolts or installing valve guides. Head needs to be perfectly flat and a fresh finish also helps guarantee a good seal with the HG. MY 2 cents .

 

[Av8ferg]

Okay, thanks for the input. I called and talked to the machinist again. I mentioned possibly not resurfacing the head and he didn’t like that idea. There is some electrolysis corrosion on the head face that he thinks should be removed to ensure a proper seal. He wants to remove as little as possible.
I asked about rod bolts and he said if they not bent or show any damage they should be fine to reuse. Sounds like getting new bolts had its own set of concerns...jeez!!



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[Av8ferg]

Engine Block is ready for paint.
I bought the POR-15 Degreaser and Metal Prep. Worked really good. The block is ready for prime and paint in the morning. Wanted to let it completely dry over night.
While cleaning and taping off I noticed an area on the block that almost looks like someone cut something off or filled a hole. See first couple pics.
There is nothing on the inside of the block there that shows anything done. Looks like someone grinders the outdoes a bit. This is in the area where the oil screen goes.
I also painted a metal bucket to test out the engine colors. You’ll see Chrysler Blue on the Left and Old Ford Blue in the Right. I also have GM Blue which I test on the bucket tomorrow.




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[madkaw]

I believe Chrysler is the closet match .

What was the final word on the head? Sounds like it needs to resurfaced . Some warpage and corrosion could lead to seal issues. He shouldn’t take enough to affect anything including timing chain . 

[Av8ferg]

I believe Chrysler is the closet match .
What was the final word on the head? Sounds like it needs to resurfaced . Some warpage and corrosion could lead to seal issues. He shouldn’t take enough to affect anything including timing chain . 

The head should be done mid week. He’s shaving it about .005 he said to clear the corrosion areas. I’m thinking the total off stock will be .010 to .012.
Looks like it was resurfaced before.

I also got Genuine Nissan valve stem seals and need to drop them off at the shop. I didn’t buy new valve springs, not sure if you really need new ones.

Nissan Bearings, front and rear Seals came in this week . Goal is paint and install the crank tomorrow and Monday.

I think you might be right on the color. GM Blue looks close too. See pic below. GM Blue in the right.



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[Captain Obvious]

I think all of that paint is too much straight-up blue, and not enough green.

If you don't have anything left that has original paint on it (like maybe the front pulley?), I found a reasonably close sample at Home Depot. I don't have the sample number handy, but I can get the name and number for you if it would help. You can't use that paint (latex house paint), but the value is in the "portable color standard" that you could get at your HD. It should be the same color as the one at my HD.

[Av8ferg]

I think all of that paint is too much straight-up blue, and not enough green.
If you don't have anything left that has original paint on it (like maybe the front pulley?), I found a reasonably close sample at Home Depot. I don't have the sample number handy, but I can get the name and number for you if it would help. You can't use that paint (latex house paint), but the value is in the "portable color standard" that you could get at your HD. It should be the same color as the one at my HD.

Thanks Captain!
I’ve decided that I’m not too concerned about getting exact stock engine color. My neighbor has an 82 ZX and the engine is 100% stock and it is probably closest to GM Blue. You can’t pick it up in the photos but it has a hint of green in it unlike Chrysler Blue which is all baby bluish. I need to get paint on this block before the rust attacks it. The POR-15 metal prep did a great job of getting the surface ready. It converted the micro rust in the pours of the casting to a polymer that is paintable. The humidity’s a bit high for painting but letting it sit too long is a worse option. I live 500 yards from the Atlantic Ocean and the salt air here is brutal on metal. I’ll post photos after.
Any clue what that area that looks like someone filled a hole. Not sure if it was that or something rubbing from the junkyard or it’s transport. I don’t see any compromise in the metal or anything else. Just wondering if other engines have this too from the factory?


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