Another Z to see the roads again...

[ETI4K]

I decided to start this thread to provide some background on some of the work I am doing/planning.

My car is an early production 76.  Back in 95, at the advice of Z Doc (Roanoke), I swapped motors from an 83 ZX, with the .080 head cut, early 280 valves, etc. and not much else in terms of performance.  The car ran well, but not as well as I imagined it would, and it was okay.  After a year or so and about 10-15K miles of daily use, I could no longer live with the rust, so I took the car off the road for a complete restoration.

As life would have it, my plans got side-tracked.  I started a business and never had the time to restart the Z project until now.

So I went into this project knowing I had a good motor.  Figured I'd disassemble and clean it, new gaskets and seals, have the cylinders honed and replace the chrome-moly rings with Total Seal (the rings never seated well).  Well, to my utter surprise and disappointment, what I found was not what I was expecting.

[ETI4K]

And so it begins

[ETI4K]

 The first issue I found was the headers had developed leaks.  Not really surprising, and no real problem as I am replacing these with Sean Dezart's.

Look closely though at the exhaust runners, then look at the water pump cavity and the scoring of the material.

  

[ETI4K]

Then the pistons.  I knew the rings didn't seat, but that's a lot of oil.  I only ever saw blue smoke on shifts.

No more than 15,000 miles. 

[ETI4K]

Well, that was the top side.  Now the bottom side.

The journals are not terrible but they had been polished.

I am not sure what the debris is on the pick-up screen, but I did save it.  At some point I will clean it of oil and examine it closely, just for edification if nothing else.

[madkaw]

2 minutes ago, ETI4K said:

Well, that was the top side.  Now the bottom side.

The journals are not terrible but they had been polished.

I am not sure what the debris is on the pick-up screen, but I did save it.  At some point I will clean it of oil and examine it closely, just for edification if nothing else.

That doesn’t look good 

[ETI4K]

My machine shop still has the motor (since January).  No rush on my end.  The good news is the cylinders were not scored, the crank journals polished out okay, the cam polished out withing spec, and the pistons are okay.

Unfortunately the towers did not fair so well.  Three of them are out of spec by .003 and each is a different size.  There is also some question that I am still trying to get to the bottom of, but it may be that the head was cut more than .080.  Like maybe another .028.  The problem is the towers were only shimmed .080.

Adding to that, the head needs three guides, and the exhaust valve seats are beat up pretty well, so a real valve job is needed.  So, in reply to @Derekquestion, I figured if the head is in for that much work, I'd prefer to have everything to spec and nice and tight.  I can make the bearings and install them so that saves me a few hundred dollars (the machine shop in OH told me making them would be a T&M job - so that's a guess).  I am familiar with the pain off trying to shoot that hone in the right direction, though I have never done it.  I think the guy quoted me less than $200 to do that work only.

[madkaw]

I would suggest getting another head . You are going to have a difficult time reinventing the wheel . You should be able to measure head thickness . 
Making your own bearings ? 
In all the years in these sites I’ve never heard of anyone putting bearings in the cam towers . 

[ETI4K]

Always open to ideas and changing my plans accordingly, though sourcing another head in decent condition sounds iffy.

The only bit that my head has me concerned about is the water pump cavity.  It will certainly reduce pump efficiency.  I know there are epoxies that are up to the task of repairing it, but I'm not keen on that idea.  It could be welded and machined back, and I could do that, though it is certainly a non-trivial undertaking.

 

 

Edited April 27, 2021 by ETI4K

[siteunseen]

I've not heard too much on exhaust seats being worn out. Intakes that are bronze, definitely but not exhaust. I guess if the adjustment was really off they could get damage? My machinist told me the big intake seats are the same as a Dodge hemi motor so they were cheap as that's a popular motor nowadays. I too would look for an older head and start over. I know where an n42 is in an older junkyard for $100 and that includes the n42 intake. My $.02.

[Zed Head]

You should measure the head thickness and check flatness.  If it's too warped you might not be able to get it straight with more cutting.  I seem to recall that the heads all started at 108 mm.  Add up your cam tower work, valve work, skimming if necessary, etc., and see what the math looks like.

The oil on your pistons could be bad valve seals.

[madkaw]

13 hours ago, ETI4K said:

My machine shop still has the motor (since January).  No rush on my end.  The good news is the cylinders were not scored, the crank journals polished out okay, the cam polished out withing spec, and the pistons are okay.

Unfortunately the towers did not fair so well.  Three of them are out of spec by .003 and each is a different size.  There is also some question that I am still trying to get to the bottom of, but it may be that the head was cut more than .080.  Like maybe another .028.  The problem is the towers were only shimmed .080.

Adding to that, the head needs three guides, and the exhaust valve seats are beat up pretty well, so a real valve job is needed.  So, in reply to @Derekquestion, I figured if the head is in for that much work, I'd prefer to have everything to spec and nice and tight.  I can make the bearings and install them so that saves me a few hundred dollars (the machine shop in OH told me making them would be a T&M job - so that's a guess).  I am familiar with the pain off trying to shoot that hone in the right direction, though I have never done it.  I think the guy quoted me less than $200 to do that work only.

I don’t see how the journals polished out . They would have cut to clean up the scratches in those pics . 
the scoring behind the water pump is not part of the head . That’s the timing cover that will need to be replaced .

you need to find out what you have before you spend money on junk . Find out how thick the head is and if it’s flat . Then a pressure check . If the towers are bad , it’s probably because the head is -or was warped . Not sure I would cut any more than .080 . 
 

Shameless plug . I do have a p90 for sale  that is shaved and ready to roll and it’s shaved .080 - with good towers ! Just PM me if interested .