Datsun Roadster Forum-311s.org

Could not have Valves been bent as well after continued cranking after the cam let loose?

Very likely on the valves. It is an interference engine.


I doubt the lifters were causing a rattle. Are the pistons domed? Piston/head contact is very common when rebuilding the R16 with OEM style domed pistons.

I can’t think of much that would break the snout off the cam other than a stress fracture.

Well, we may have found the issue. Doing as Dean suggested, I see that the cam locating plate is galled badly meaning there was no play between it and the sprocket. It over heated and finally froze together twisting off the end of the cam. Since everything was installed correctly...I checked. I think I may have received the wrong sprocket???. I attached a couple pics for fun.
The noise I had that sounds like loose lifters we are guessing is due to worn rocker shaft. Will replace that and see if it fixes it.

Thanks for the comments!

This is exactly what I suspected happened. Tight too tight ...broke! That is why I asked you to look at the retaining plate and the sprocket. This does not look like a Nissan sprocket or any for the R16 that I have seen. Actually looks like a nicely machined sprocket. I would ask the person you bought this from where this came from.
After installing the sprocket onto the camshaft always check that the assembly rotates freely and that it has end play.
You are going to need a new camshaft thrust plate, cam of course and a set of new sprockets.

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Yes, that galling is pretty bad. My guess is there was insufficient (or too much) end play when assembled.

I''ve seen lots of galled components over the years, but none that resulted in overt cam failure. (they usually just gall the plate and the back of the sprocket)

Was the cam locating plate mounted correct?
Wrong bolts are used so maybe the plate is turned arround.

JT68 wrote: Tue Feb 23, 2021 1:05 am Yes, that galling is pretty bad. My guess is there was insufficient (or too much) end play when assembled.

I''ve seen lots of galled components over the years, but none that resulted in overt cam failure. (they usually just gall the plate and the back of the sprocket)

I've seen this happen twice before. That is why I asked what the thrust plate and back of the cam looked like. I spoke to Scott and the assembly was too tight. He told me he ran this for 30 minutes. Imagine the heat generated in the snout after 30 minutes.

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richard wrote: Tue Feb 23, 2021 1:35 am Was the cam locating plate mounted correct?
Wrong bolts are used so maybe the plate is turned arround.

Richard those are the correct bolts. I think you may be thinking of the U20 jackshaft thrust plate that is beveled where Philips machine screws are used to fasten it in place. https://www.datsunparts.com/2649

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