L28 from 82 ZX teardown

[Av8ferg]

A little lite wire wheel and elbow grease and these cleaned up nice. All cracks are no longer visible.

 

 

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[Captain Obvious]

I think that timing cover is fine. Those little lines are just imperfections from the original casting. I see you already sanded them off. Good... Non-problem.

As for the hex plugs in the intake manifold... As mentioned above, they cast a cavity that runs the length of the manifold to distribute the recirculated gasses from the exhaust (EGR). But that cavity does not have any connection up to the intake runners because it was impossible to cast that way. So those plugged holes are the access holes they used to add in the holes between the shared EGR log and the individual intake runners.

I haven't pulled those plugs or sectioned a manifold to see for sure, but I wouldn't be surprised if the holes they drilled up into the runners are different lengths depending on how far they are from the EGR valve. Just a guess on my part.

In any event, they drilled small access holes up into the runners and then tapped and plugged the access holes below. And they thread-locked the steel hex plugs in place. I tried to take one out as well and couldn't get it out. I suspect a bunch of heat would make them easier to get out, but I was doing this on the car. Next to the fuel rail.   

[Captain Obvious]

@Av8ferg, Last page you were talking about rod bolt positioning... I was messing around with my pistons a little today and I came up with what I believe is a reliable witness mark for the rod bolts rotational position.

During installation of the rod bolts and nuts, it's the oval shaped head of the bolt that keeps the bolt from turning while you tighten the nut on the other side of the bearing cap. Because of this feature, the oval bolt head contacts the rod in one spot as the night is tightened, and (on my pistons at least), this resulted in clean spot witness marks where the two were in contact with each other. Here's some pics.

During tightening, the bolt head will rotate in the recess in the bore in the direction of the tightening torque applied. Looks like this:

And because of this, there's a little clean spot on the connecting rod where the bolt oval made contact:

And a corresponding clean spot on the oval bolt head:

It's pretty small and you might need some magnification to find it, but if yours look like mine, you should be able to use these marks to determine the original rotational position of the bolts. Assuming you've got the original bolts in the original holes, this should allow for positive ID for original rotation.

[Av8ferg]

Captain, I’m going to look today and see if there is any marks like that on mine. I thought I took a close look already for witness marks but now I know exactly what to look for, thanks.

BTW, I grabbed a non-EGR head from one of the 75s in that yard. They only wanted $40 (that’s for the intake, heat shields, throttle body, injectors and all sensors on the head) so I figured why not grab it. Haven’t decided if I’ll use this or the ZX intake.

 

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[Av8ferg]

So, I got a call from the machine shop about my engine and it appears there is a problem with the head,  The mechanic said one of the valve seats was protruding into the chamber by about .1000”.  Said the head had been worked at some point in its life and someone did a “hack job” putting in this new valve seat.  He said the can replace it and recommend doing all of them and then they would grind the valves also.  So they want an extra $240 to do this over the $220 I was already going to pay,  My question to the crowd should I proceed and allow them to do this work or abort and find a different head.  The guy doing the work said he rebuilt a L28 last year and they can do the work, 

I really don't know much about this topic and only have read in the Nissan engine rebuild book by Tom Monroe that replacing valve seats is strictly the professional machinist.  I really don't know much about this shops specific reputation or how much they really know about these Nissan engines,   “The Captain” fielded an emergency call from me today to help me understand what the machinist was saying and called him back to verify it.  Much appreciated CO!  

I might drive to the shop tomorrow to get pics.  

 

 

[wheee!]

Captain, I’m going to look today and see if there is any marks like that on mine. I thought I took a close look already for witness marks but now I know exactly what to look for, thanks.
BTW, I grabbed a non-EGR head from one of the 75s in that yard. They only wanted $40 (that’s for the intake, heat shields, throttle body, injectors and all sensors on the head) so I figured why not grab it. Haven’t decided if I’ll use this or the ZX intake.
 
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Those clean up real nice....

[siteunseen]

On 10/13/2019 at 8:24 AM, Av8ferg said:

Captain, I’m going to look today and see if there is any marks like that on mine. I thought I took a close look already for witness marks but now I know exactly what to look for, thanks.

BTW, I grabbed a non-EGR head from one of the 75s in that yard. They only wanted $40 (that’s for the intake, heat shields, throttle body, injectors and all sensors on the head) so I figured why not grab it. Haven’t decided if I’ll use this or the ZX intake.

 

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There it is! $40 too. 

Keep it simple.

 

[siteunseen]

My machinists used Manleys for a Dodge Hemi motor I believe is what he said. He had to cut my E31 for the larger seats. I am pretty sure he charged $10 per hole. He said for new valve seats it was important to lap the valves for a good seal. It's still sitting on a shelf in my spare bedroom.

 

[Av8ferg]

So I got my block and crank from the machine shop today and got to peek at the head to look at the issue it has. Crank was great said said the journals were spot on and consistent across the board. Block looks good, no issues there.

As far as the head. It’s been worked before the deck was fine but he wants to resurface to get it prefect. It’s been resurfaced before it appears. Deck measures between 4.249” to 4.250”. I’m told the factory head is 4.255. So he wants to take about another .005” off. Total would be .0010 off of stock. One valve seat is jacked up. See pics below. The one seat is sticking out and there is a gap behind it between head and seat. He doesn’t think all should be changed but there is some corrosion so he is going to clean up the rest and do complete valve job. Total cost for all this will be $300.

Any thoughts from the pros out there. Option 2 would be to resource another head and start over but the machinist thinks this head is fine otherwise.

 

 

 

 

 

 

 

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[siteunseen]

I'd go with the machinest's opinion. Head looks nice in your photos.

[Patcon]

I would too.

You don't know that another head will be any better or any cheaper than where you are already at. I try to take my stuff to people I trust and then rely on their expertise. That's really what I'm paying them for...

[madkaw]

Might want to be sure what you intend to do with the motor since he’s going to shave it. Want to raise the CR more than just a .005 cut? Now is the time . It wouldn’t cost anymore to take .020 off than .005

Not even sure what I’m looking at with those seats . So that raised portion is actually part of the seat? WTF! 

Head looks pretty clean other than that.