Complete Misfire on Three Cylinders

[Mark Maras]

Nissan cam or aftermarket?

[Patcon]

Well that sucks!

[Captain Obvious]

I bought this car used a couple years ago, and I don't know the history of the engine. I did get some pics from the PO including some shots with the head off the engine, so I know it's been apart at least that far. I don't know if he ever pulled the cam off the head or took the towers off the head. It's stock parts (cam is Nissan "A" grind stock), but I don't know if it's original to this car. I suspect that it is, however.

I've been driving this car on that engine since I bought it, and have never had a hint that I had trouble like that brewing. No idea what happened. I was not at high RPM's when it let go, and I don't think I've ever hit redline with that engine. I take it to maybe 5K often, but that's about it. Anyway,  no idea why it finally let go, but it's gone now!

So I haven't dug into it at all and don't know if that rear cam section is seized in the journals. I kinda doubt it. I suspect it spins just fine. I'll find out when I start taking stuff apart.

And about a path forward... I could either put a new cam in that engine, or...

15 hours ago, Av8ferg said:

may be that this is what brakes the inertia and gets you starting that F54/P90 engine rebuilt and in your car?

Exactly what I was thinking as well. I kept telling you I was going to do it this summer, right? The only problem is that it's Z driving season right now and it would be faster to toss another cam into my existing engine.

15 hours ago, Av8ferg said:

If you gave me 100 guesses without that video on what caused that I would have never said.... “oh, easy a cracked cam”

Yeah, me either. That's the "whatever remains, however improbable, must be the truth."  part!  

Edited May 17, 2019 by Captain Obvious
My cam is an "A" grind

[Dave WM]

I still think its the AFM that needs adjusting.

[Captain Obvious]

Haha!!!  

[Av8ferg]

Well, for sure put a new cam in it. That’s the fast way to go and you’d likely keep this engine as a spare I presume anyway.

So, what intrigues me is what was the mechanism for the failure. Is it possible something got in the head and jammed the cam for a moment. Why did it break where it did? Either the cam experienced some sort of trauma or it was faulty and had a small stress riser that finally gave way.
I took a 4 week course on aircraft accidents and we had a structures class that focused on metal fatigue and a lot can be determined by looking at the fracture. You can tell If it failed slowly or immediately. I’d think the area most prone to cam fracture would be where to sprocket connects. This is where the load is being applied.




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[Dave WM]

I am sure CO is going to do a post mortem with detailed looks at the fracture, its his nature.

[Dave WM]

so now I have to get a spare camshaft for my spare head for my spare engine....Paranoia is a difficult thing to overcome.

better still, Camshaft phobia..

Edited May 16, 2019 by Dave WM

[Av8ferg]

Might as well get a spare Z while your at it. An hour from my house I found a 76 the yard will deliver to my house for $800. Minimal rust and tighter 100%. Tempting but my wife would for sure stab me with a dull spoon if it did it.


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[Dave WM]

you will get no help here in support for NOT getting it. Make a deal she can get a new couch if you get the car. I use that one a lot. Some how the couch deal never happens though.

Edited May 16, 2019 by Dave WM

[Dave WM]

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

[Mike]

If it was mine, I'd go get the head or engine rebuilt.  Some of those valves may be bent.