Datsun Roadster Forum-311s.org

Okay first the details. 67 r16 . Engine ran had no real noise prior. But burning a bit of oil and low comp cyl leakdown @ 30% on #3. So decided to disassemble
Went thru motor. Broken ring on 3. But fortunately no cly wall scoring etc and mic’d out pretty good.
Cam had some pitting.
So went w new cam, lifters timing comp kit, rings, brgs (std) -
Also had head work (machine shop) put in new valves , guides were okay but replaced springs and seals. All parts from Dean so i know quality is good. Head had very light resurface , block same basically to clean up.
Reassembled all went well. But upon start up. Quiet for first 3o-60 secs. Then loud higher pitched knocking at anything over about 1000 rpm.
Freaked thought perhaps there was too much machining and either valves were hitting pistons for clearance issue. So removed head inspected all seemed OK no signs of any contact. Also just to make sure I did not measure anything else improperly I did plastic gauge bearings and all were at .0015 or better. Took head back to machine shop he said everything was OK but not sure how far he looked. Also ensured my valve lash was set properly at .017”.
Reassembled. No smoking gun ... and of course noise still there.
In order to not make thia post any longer than it already is. Would like your thoughts before i decide what to do next. Ill try and post link to video.
Also i have another 70 r16 motor that was running before the car was totaled while i was driving. Thinking of swapping heads to see if this is a valve/upper end issue or in the lower end.

Sounds like valve lash. Actually, sounds like my R16 to be honest.

have you used a stethoscope to try and isolate cylinder??

Yes def from rear of eng , 3-4. Most prom by head @ say near spark plug area. And it def much louder than it ever has been. Also doesnt seem to change much if i pulll plug wires of each cyl. And can retard timing all the way back to zero with no change either. Pulled rockers back off as well they had slight wear on pads. But i was able to polish off with emery cloth. Just in case it was either affecting my valve lash setting or causing a snapping on the valve stem.

Exhaust leak?
Dan

Some possibilities for checking until the cavalry arrives:
Check the push rods to see if any are bent
Pull the oil pan and have a look from down below
Check oil for shavings
Also distributor was installed correctly? It must be seated all the way down
Linda

Thanks Dan , nope very distinctly metallic. All new manifold gasket each time as well and no signs of ex leak either. Its also to me higher in pitch than lower end. In my experience.
Thanks Linda yes oush rods were checked roll straight and narrow. All measure sameheight. As mentioned pan cam off plastigaged all brgs. Pulled pistons checked cyl walls and skirts. No metal in pan beside slight glitter(new rings seating) all caps reinstalled and torqued correctly.
Whatched timing marks at rpms where it occurs. No fluctuating as if new tensioner was not working or dist not seated.

The rocker shaft oil feed screw might be missing or loose. Do the rockers all get oil?
Linda

. Screw there, all rockers getting good oil , and were pulled apart aftwer hearing noise the first time. When i polished the rocker feet. Pic of prior to polishing attached as well.

Well, I feel like I need to chime in after all the help I received on diagnosing my engine noise. First off, I feel your pain! Since you have another head you might try just swapping the rocker assembly instead of the whole head. Good luck.

Actually sounds like a wrist pin to me.....

boxcar wrote: ↑Fri Apr 06, 2018 8:20 am Actually sounds like a wrist pin to me.....

that is one area i was leaning after thinking last night. when I bought the engine package from Dean, it was the one that came with the flat top pistons( which i did not use, any body intrested btw? ) . But when i sent block to machine shop to have him do a light hone on cyl. i sent my pistons for him to look at , he did say he pulled them apart but they looked good. I think he used the new snap rings( i hope ) from the new pistons. does anyone know if the flat top new wrist pins will work in the domed pistons? i could try and swap... whats one more head gasket

theunz wrote: ↑Fri Apr 06, 2018 8:00 am Well, I feel like I need to chime in after all the help I received on diagnosing my engine noise. First off, I feel your pain! Since you have another head you might try just swapping the rocker assembly instead of the whole head. Good luck.

not sure if i can one is SAE studs other is metric.

I'm at work so I cannot hear this super well, but to me it sounds like valve slap, ie too much lash. What happens if you tighten them down more? What lash are you running? As long as you have some lash, you will be fine, so don't worry about tightening them up some more just to see what happens. Do leave some lash so the valve seats, but just try this to see if it makes any difference. I suspect something in the valve train, though I am very unfamiliar with push rod engines vs the U20. If you had not taken the head off and had it inspected already, I would be wondering about a loose valve seat. I see they replaced springs and seals, but no mention of valve seats. The original were brass and they heat at different rates than the head, causing them to have more chance to come loose and slap about. I can't imagine that they did not notice one, especially since I would assume they recut them, but you never know. Your problem was with #3, and it sounds like the noise is at the back part of the engine. I have no idea how you could check for a loose seat without pulling the head again... only thing I can think of is to pull the carbs, get a snake style inspection camera (harbor freight?), put each valve such that it is open and off the seat, and see if you can detect any problem, maybe be able to push against it with a thin screw driver (?). It does not sound like a rod knock, which will typically change with RPM changes (reving). Sounds like one cylinder... I would concentrate on rockers, pushrods, valves and seats. Sorry to hear, but least you are capable of fixing it! (engine looked great BTW).