I didn't say it was uncontrolled.  I said the spec. was set wide.  It' not economical to set a tight tolerance where it's not necessary.

So I started stripping the valves out of the head. Next chance I get, I'll post up some pics of my home-brewed valve tool, but in the meantime.....

So I'm taking the valves out, and here's the springs from a couple of the valves. I never even knew the springs had a variable pitch and a "proper direction" to them, and apparently neither did my PO. The retainer caps are at the top for both of these, but the pitch direction is different between the two:

I'm not sure how much difference it makes in the grand scheme of things, but just another detail that was missed.

What's the backstory on the car?  I wonder how deep the PO got in to the engine.

I realized the inner spring was free of the outer ones. Got them all the same just eyeballing. So far so good.

I think that's the cause of lash pads jumping out too.

I will do some more measuring usint my 4-5" Mitutoyo mic. Will measure a few thought to be uncut heads tonight.

Measure each end and you'll also get an idea of the tolerances for an individual head.  If they're not tight within a head, they won't be tight across many heads.

  On 7/10/2019 at 7:31 PM, Captain Obvious said:

So I'm taking the valves out, and here's the springs from a couple of the valves. I never even knew the springs had a variable pitch and a "proper direction" to them, and apparently neither did my PO. The retainer caps are at the top for both of these, but the pitch direction is different between the two:

I'm not sure how much difference it makes in the grand scheme of things, but just another detail that was missed.

 

The narrow pitch side of the spring goes down against the head. Wide pitch side is up connecting to the retainer.

So, I measured two heads, both of which I am pretty confident  that they haven't been milled. Can't be 100% certain since I didn't buy either as the first owner.

I will reference cam tower numbers and cam tower number 1 is closest to the sprocket.

First, my new old stock in box E88. Nothing to clean here. 

1=4.2474, 2=4.2471, 3=4.2475, 4=4.2478, 5=4.2479

 

Second, my N42 head from the 75 280z with 55k miles I am refreshing. N42 heads were generally used on 75 and 76 280z models and are the same as N47 except for shape of exhaust ports and liners in N47. I want to also mention that I only took two measurements because getting a stamp sized spot to be as clean as my new E88 head took a decent amount of time and effort. 

2=4 2479, 4=4.2478

Bottom line, I think these two heads and CO's N47 head are uncut / unmilled.

Hope this is helpful. It was an interesting exercise for me.

 

Well this is great news that you have no piston / valve damage and are getting your car back on the road.

We are all at the mercy of the POs’ shortcomings / shortcuts! Mine had done some pretty scary things too - especially on electrics - things like adding a 50A fuse for the washer pump ‘cause the 5A kept blowing (he didn’t bother trouble shoot/cover his hacked about naked wiring that was intermittently shorting out)!!!

Keep at it fella - looking forward to hearing about her growling again!

Thanks all for the encouraging words, and thanks also for the additional investigative work on the head thickness. I guess the bottom line is that I've got a reasonably high degree of confidence that my head was never planed. Surprising to me that the PO would get as deep into the head and NOT have it cut, but thankful for small miracles. Just one less thing to get screwed up under his ownership. 

  On 7/10/2019 at 9:49 PM, jonathanrussell said:

The narrow pitch side of the spring goes down against the head. Wide pitch side is up connecting to the retainer.

Right. I saw that in the manual. The point of the pic is that so far I've taken out one of each direction so far. My PO apparently didn't know they were unidirectional and just tossed tehm in random. I will put them all in the right way when I put this thing back together.

  On 7/10/2019 at 7:53 PM, Zed Head said:

What's the backstory on the car?  I wonder how deep the PO got in to the engine.

Back story? Typical. I bought it a number of years ago with very little detailed info about it's history. I got a couple pictures from the PO taken during some of the work he did to the car, and a couple of the pics show the head off the engine, so I know he did that much.

I also have a stack of receipts that include ONE piston and rings for said piston. So I don't know what goes wrong with an engine that requires the replacement of just one piston, but the implication is..... My PO has been into the bottom end as well.     Kinda makes me wonder what kind of trouble lurks down there.

All that said... I didn't buy the car for the condition of the engine. I bought it for the condition of the underside. It's pretty much rust free. To me, everything else is easy.

So anyone got a recommendation on valve seals?

Nissan genuine?
Doesn't matter, all the aftermarkets are fine?
Low profile Ford (I think?)?

Viton? Anything?