L28 Rebuild? Swap? Leave Alone?

[siteunseen]

Would the fuel injector holes on the N42 head have to be welded up or is that not too important if the intake manifold covers them?  Curious.

[Ptero]

Amazing what adjusting the valves can do!  It seemed the clearances were way off initially.  Couldn't even fit a .006 for some of the intake lobes.  I adjusted the valves to .010 for intake and .012 for exhaust.  Yes, I know those are what they're supposed to be hot but, I was trying to loosen them as Blue suggested.

 

Here are the new numbers after the valve adjustment:

 

1 - 146

2 - 165

3 - 157

4 - 147

5 - 132

6 - 137

 

Things are looking a lot more even than when I first started but, still not ideal.

[240260280z]

Often they will seat better after running a while. You are on your way !

[Zed Head]

I don't think that you'll get good pressure numbers from an engine that's been sitting, turning it with that gear reduction starter. 

 

 

Some other things you might examine are the backs of the valves, for carbon deposits, and the tops of the pistons, what you can see through the plug holes.  If they're all crusty and caked, the engine has some miles on it, if they're shiny and look good, maybe somebody just put it back together and ran it for a few miles.

 

Look at the chain guides from the top, see how much plastic is left.  High mile engines will wear the guides down.  Check the notch and groove for alignment and hole number, that will give an idea of chain wear.  The valve train area looks pretty clean, no signs of sludge.  That's a sign.

[Ptero]

Valves & pistons look pretty dirty but I'm not sure what's a normal amount of carbon build up.  Whatever was on the pistons was pretty soft so I'm wondering if that would just burn off or get blown out once it was started.

 

 

 

Pics are not great but I was just using what I had kicking around.  First piston picture is the cleanest one and the 2nd pic is what most of the others look like.

 

 

 

 

What's normal wear on the timing chain guides?

 

 

 

 

Can't see that well from this picture but the notch is slightly to the left of the marking on the cam when at TDC.  About half of the notch was to the left of the marking.  I don't fully understand these numbers and markings yet.

 

 

This is where the timing marks are on the damper but which notch is the one that is supposed to be used?

 

 

 

I'm starting to think I might toss this engine in the car to see how it runs and end up rebuilding my other engine that's in the car right now.  It's been leaking oil from a number of places for a while and could use some refreshing.

[Zed Head]

Your chain guides actually look in really good shape.  The used ones I've seen all have grooves worn in them from the links rubbing.  

 

The damper pulley looks like a problem.  I don't know if Nissan put zero at the same spot on both styles or started from scratch with each design.  I think that you could get a 240Z pointer and be right, assuming the damper is in good shape.  But it's always good to confirm the TDC mark is correct.

[Ptero]

The engine was at TDC for both the damper & cam marker pics.  I'll grab the 240z marker from my other engine to see where it lines up here.  Or would this mean that the 2nd notch from the right is the correct one as the engine is at TDC in that photo?

Edited March 11, 2015 by Ptero

[Zed Head]

How do you know it was at TDC?  The piston barely moves up or down over a pretty wide range of crankshaft rotation.

 

Just saying, that's why they use "dead center" to describe it.  It's a very specific location.

Edited March 11, 2015 by Zed Head

[Ptero]

How do you know it was at TDC?  The piston barely moves up or down over a pretty wide range of crankshaft rotation.

 

Just saying, that's why they use "dead center" to describe it.  It's a very specific location.

 

I put a pencil in #1 spark plug hole and slowly moved the crank until the pencil didn't move up any further.  Super scientific!  I know!

[siteunseen]

The biggest notch at the far left is 0 on the 240 damper, then 5 degrees for each smaller notch moving up clockwise.  It looks about right compared to mine but like Zed said there is a "perfect spot" for TDC.  I'm thinking with the keyway on the crank it would put any damper at the same position, a 240 or a 280 damper.

The white spot in this picture is past TDC, my timing chain was advanced a tooth or two from the previous owner.  Caused me a big ole headache, never could get the timing adjusted right.  Now I'm rebuilding it.

 

Edited March 11, 2015 by siteunseen

[Ptero]

I'm gonna try this method later to get a more precise TDC.  

 

"Now pull the oil dip stick out and put it in the # 1 spark plug hole. Put a 27 mm socket on the crankshaft damper pulley bolt and turn the engine clockwise with a ratchet until the dip stick just starts to go down. Put a chalk mark on the damper pulley where 0 TDC pointer is.

Now turn the crank the other direction (counter-clockwise) until the dip stick starts to go down again. Mark the damper pulley one more time. Exactly half way between the two chalk marks is true TDC."

[siteunseen]

I used a drinking straw cut in half.  I think a dipstick would be too long and fall out.  Maybe a short screwdriver but metal on top of the piston getting bound up would suck.  But I'm a little too cautious, it causes me to drink a lot.