Datsun Roadster Forum-311s.org

Picked up a loud tap after a long, hot drive yesterday. I checked the rockers and while I do see some work ahead in the future, and a new cam, I don't think that's the problem. The link is to a video I took last night. You can hear the sound at idle and it's much louder at higher RPM. The engine's running well, but for how much longer? I'm near Watkins Glen, trying to sort out the rest of the weekend and the trip home to Virginia. Might limp over for this evening and/or tomorrow's events (and potential help). Just wondering if what the collective had to say about the noise before I drove too much more. Any thoughts welcome and appreciated.
https://pilot168.smugmug.com/Roadster/i-zQmMMVn/A

Matt

Pull 1 plug wire at a time ,to see if it lessens or looses the knock
If so that's a rod ,possible a nut went into the cyl
at higher rpms it stays about the same ?
possible valve seat or guide loose , or anomaly in the valve train
Use a stethoscope to try to localize it

Knock was pretty much unchanged through the test.

When you said checked the rockers, did you check the valve lash?

It sounded weak running to me
I do a completely cold compression test it's so easy to do why not
note the 1st pump psi ....possible a rusted cyl from setting centrifugal advance free & working?

Didn't check the valve lash at this time and compression has been pretty good. I'm out of town at the moment but will check what I can in the morning. Best candidate for the noise seems to be some nasty pitting on a cam lobe. The top end had shown enough wear when I bought it last year that I knew that its time was coming. I guess a long drive in hot weather got me to the rebuild sooner than expected. I guess the upside is, new parts!
That's my glass half full mindset at the moment.

+1 for valve lash

I will predict you have a rocker that the hard face has worn and that is the noise you are hearing.
Dave

are /have you turned the engine over with bump starter to see if a ,.002 of " larger feeler guage goes in at any point

After having gone through a "what the hell is that tapping noise" nightmare... I agree it sounds like valve train related and likely a rocker/cam lobe issue. It does not sound like my fractured wrist pin. I would pull the cam cover and check lash etc if you have not. If you don't see anything obvious then I might become concerned about a loose valve seat... I don't know if it could be found without pulling the head.

The car got us home and I couldn't be more proud of her. I think all of your collective thoughts regarding the valve train are on target. The cam wasn't looking too good and I'm pretty sure that the rockers have probably lived a full life, and then some. I'll get in there and take some pictures in a few days when I get a chance to get under the hood. In the meantime, thanks for the advice and tips. This forum rocks. Cheers!

If you're really stuck Joe Russo lives in Watkins Glen. JRUSSO07@ROCHESTER.RR.COM

Okidoke, here's the update. Oooo boy. I was wrong originially. Must not have seen it for the oil. This is my first roadster so I hadn't adjusted the valves before, only seen them done. When I checked the lash I was getting the proper clearances but apparently that was only on one part of the rocker, in the center where there was a tiny bit of surface left. There was apparently some side to side rolling involved in the movement on the most problematic rocker. So, the one piece rockers were toast, two really bad and I had a nasty pitting on one of the cam lobes. A local Datsun whisperer friend hooked me up with some matching rockers and a cam and we're back on the road. This should hold me over as I cobble together the money and parts for the inevitable full rebuild. But in the meantime, it's roadster driving weather. Below are photos of the carnage for the collective memory. I appreciate the help from you guys as we were out of town. We salvaged a good time and made it home thanks to your help.
Cheers.

No your rocker arm geometry is off and that’s what destroyed them. Your engine must have a re-ground cam in it where the base circle was reduced enough that thicker lash pads would be required.
Dave

david premo wrote: Sat Sep 16, 2023 7:16 pm No your rocker arm geometry is off and that’s what destroyed them. Your engine must have a re-ground cam in it where the base circle was reduced enough that thicker lash pads would be required.
Dave

Thanks for the insight and input. Forgot to mention that the lash pads also came with the transplant set. There's a lot of work ahead on this one. I don't know the full history of this car and it's apparently got some oddities. It's an early '68 with a '67 hangover in a few places. Someone has obviously been in the engine before so I'd imagine there are some more uncovered mysteries. In a few months I hope to be able to get it properly rebuilt. I promised her some new parts if she got me back home. She held up her end and I'm looking forward to repaying the favor.