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Captain Obvious

Complete Misfire on Three Cylinders

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Drive 5 hours and bring your bug repellant


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Metal fatigue is a whole different world than metal strength.  If the cam towers were off a little bit that small bending motion could fatigue the shaft over a few billion revs.

Turning the back half by hand/wrench might show if a valve is bent.  Might help with planning the repair, if you want to do it all in a short time.

On the other hand, you could just unplug the back three injectors and drive it that way while you pick up parts.  

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15 hours ago, Captain Obvious said:

Sorry guys. I was trying to be cute and I guess the issue doesn't come across so obviously in the video. That's what I get for holding my antique crappy  camera in one hand and reaching in with my other hand to crank the engine.

Seriously? It was totally obvious (Captain) that the back half of the cam wasn't turning! Three seconds in I was shouting "WHAT??" I have never seen that...

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18 hours ago, Captain Obvious said:

That's what I get for holding my antique crappy  camera in one hand and reaching in with my other hand to crank the engine.

That's what she said. LOL

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11 hours ago, Dave WM said:

CO, do you have a spare camshaft that you can install? just want to know if there is ANY binding that you can detect.

No, I do not. The one in there is an "A" grind from 1977. I've got an F54/P79 combo here from an 83. That might be the same cam, but if I'm going into that motor, it's for the intention of dropping it in where my existing motor is.

9 hours ago, Av8ferg said:

I’m pulling that N42 head next time I’m away for work. There are 2 N47’s in that yard. Meet me there and we’ll pull them both. $70

LOL. Maybe I will! Bug spray and sunscreen!

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7 hours ago, cgsheen1 said:

Three seconds in I was shouting "WHAT??"

First time I hit the key, I just wanted to see everything rock around like it's supposed to. It was so striking that I had to do it again. I was like "Wait.... What???" I was stunned. Took a couple seconds to sink in, and then I was really bummed.

So what are the prospects for bent valves? Is the L28 an interference engine?

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32 minutes ago, Captain Obvious said:

So what are the prospects for bent valves? Is the L28 an interference engine?

Nissan implies that it is.  Are you planning to pull the head or just go ahead and swap engines?  Did you look for stuck valves?  Seems like if the shaft broke in the wrong spot a valve would have got bumped.  Don't forget, we love destruction, even though it means more work for you, so take more pictures.  Weren't you getting bored anyway...?

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I haven't decided what path forward I'm going to take, but whatever that path, I will be sure to take pics.

I did not look for stuck valves. I haven't done anything else beyond that short video clip other than go out to the driveway and open the hood on the 83 and look inside.

I was NOT getting bored. I'm so backed up with car work at this point that one more thing is absolutely not desired at this point. In fact... I'm cleaning up after dinner last night and the hot water coming out of the tap is way hotter than usual. Dangerously scalding hot. Take a look a the water heater and it's got water dripping from somewhere out the top. Not good... I killed the breaker.

SWMBO isn't going to appreciate cold showers. Especially if I'm out in the driveway working on my car.   :facepalm:  Anyone want to help me wrestle a water heater down into the basement? I'm getting too old for this crap.

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3 hours ago, Captain Obvious said:

I haven't decided what path forward I'm going to take, but whatever that path, I will be sure to take pics.

I did not look for stuck valves. I haven't done anything else beyond that short video clip other than go out to the driveway and open the hood on the 83 and look inside.

I was NOT getting bored. I'm so backed up with car work at this point that one more thing is absolutely not desired at this point.

That does suck then.  The quick and dirty fix, if no valves are bent, might be a cam shaft swap.  I think.  Slide the old parts out and the new parts in.  Might as well loosen or remove the towers then use the tap, rotate, and tighten method to be sure it spins free.  If you brought the rocker arms over with the camshaft, it might not even know it's in a different engine.

I've looked at a bunch of cam specs and they're all about the same.  I think the ZX's were probably changed for better emissions, nothing dramatic.  After the mid-70's, most changes were about emissions.

It would be an interesting challenge, to see if you could make the swap without destroying another camshaft.  The key to finishing it is to avoid the while-I'm-heres.

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I’m gonna guess that there is likely some valve damage considering you drove it for awhile to get home but maybe I’m wrong. I think it’s a head removal anyways s time will tell. I fully expect a detailed report post removal.

I know you got car issues besides the Z, hope you get some free time to hash them all out.


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I think it depends on how fast the broken piece stopped spinning and how extended the open valves are.  Inspection will tell.

The back cam tower could be removed and the broken half lifted out, I think.  That might be fun.

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On 5/15/2019 at 9:54 PM, S30Driver said:

Wow. must have been weakened from those 10,000 rpm shift points of your spirited driving .LOL

Only thing I can think of is a bearing froze after the break or a flaw in the metal that decided that was the time to let go.

 

 

Atlanta in Zup's car? LOL

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Maybe the cam had been dropped at one time and was cracked - and it finally gave out. 

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18 hours ago, siteunseen said:

Atlanta in Zup's car? LOL

Shhhhhhh.....     LOL

Zed Head, I could take the back half of the cam out easy. Maybe I'll do that (if I can sneak some time in the garage when I "should be working on other things")

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