Datsun Roadster Forum-311s.org

We keep agreeing with each other! Rotate the engine around by hand via the crank bolt and you can watch the top half of the engine stop turning as the tensioner shaft is pushed back and forth into the housing due to the resistance of the valve springs on the cam, and it will suddenly snap and rotate (the cam) as it overcomes the spring tension. The oil pressure keeps that from happening, but before oil pressure is up (as on start up) that shaft is helpless, and thus the need for the shims to keep this movement small.

nismou20 wrote: ↑Thu Apr 06, 2023 9:21 pm The rubberized chain guide material still there? Valve clearance clatter? Any chain wear marks underside of Cam cover? That’s a head scratcher!

It looks like the chain guide material is still there. I am not sure if there was any clatter from the valves due to the clearance, I had checked them when the motor was in the car when I first got it the car running. There are a few scratches on the inside of the cam cover, but I don't know if they are new or were there before I got the car.

I turned the motor over to TDC and took a few pictures below. I did notice that on the front chain that one of the links looks to be missing a piece. I have circled what I am talking about in red.

jrusso07 wrote: ↑Fri Apr 07, 2023 10:37 am As Greg said, could be accessories rattling. My carb heat shield would rattle on de-acceleration due to a loose mounting bolt. Also, pin holes in the exhaust can cause air whistling and chirping noises. Did you have the air galley still installed (assuming you had the smog head with the smog distributor). Those too can make chirping noises if the air pump is removed or not functioning. Might sound like a rattle if the frequency is high enough...

I checked what I think is the carb heat shield under the carbs (metal rectangular plate under carbs), and it is attached good, no wiggle. I am not sure what the air galley is though. I believe all the smog stuff was removed and some bolts were put in the intake where it would have been installed.

DO NOT START THE ENGINE UNTIL YOU REPLACE THE UPPER TIMING CHAIN!!!!! Wow are you lucky, buy a lottery ticket. The chain has a master link and it has come apart. You could do major damage to the engine if the chain fails. Such as parts flying out the side of the engine.
Dave

Best to check the crank gear teeth
1st in the 80s a lot didn't resemble what a new one looked like

david premo wrote: ↑Sun Apr 09, 2023 8:41 pm DO NOT START THE ENGINE UNTIL YOU REPLACE THE UPPER TIMING CHAIN!!!!! Wow are you lucky, buy a lottery ticket. The chain has a master link and it has come apart. You could do major damage to the engine if the chain fails. Such as parts flying out the side of the engine.
Dave

Well sounds like I just dodged a serious issue! Looks like I will be replacing the timing components after all. I was also curious if the chain tensioner was working properly. I took a video of me turning the engine over and looking at the tensioner, I was curious if this is how it is supposed to operate. I tried to upload the short video here but I dont think I can. I posted it here and hopefully the link works (never tried before!)

https://youtube.com/shorts/tiCR3JOBgbQ?feature=share

Yes you dodged a potentially catastrophic issue. When you replace the chains and possibly the gears, as they can easily be evaluated once you have a new chain by observing how the chain lay on the gears. Worn gears will not let the chain lay properly on the gear and will quickly wear out the new chain. Not knowing what your budget is, it’s always best practice to replace both gears and chains along with guides and tensioners. I think the old saying was “an ounce of prevention is worth more than a pound of cure”. All of the timing components were very expensive not too long ago, but now I think they are quite affordable.
Dave

You should drop the oil pan and look for the plate and the clip that came off the chain’s master link. The timer on that bomb was down to seconds!!

Hey ya, wow... THAT'S PRETTY COOL! Usually you just see the final result from a broken chain... whew!
The YouTube you posted is EXACTLY what I was saying about what happens with no oil pressure on the tensioner and why you need shims. That action is what caused it to undercut the "evil" L in the first place. Thanks for documenting that, now people will have a visual as to why shimming the tensioner is critical.

BTW, for a "novice" you're doing great work. I think (hope) you're going to enjoy working on the car and should be successful. We're all ready to help!

I'm wondering if the missing piece on the master link is the root cause of the rattle...? Might that 4K rpm rattle it be an early indicator of impending destruction.

1st off thanks everyone for all the comments and help! I can take the oil pan off this weekend and see if I can find that chain piece. I have never replaced a timing chain on a car before. Is it difficult job on these motors? Does the cylinder head need to come off in order to replace all the timing components? The reason I ask is that I did a compression test before I pulled the motor and was thinking that the values were a bit off (I think I read somewhere on the forum that the numbers should be within 10% of each other).

Welcome to the can of worms. The head gasket or head does not have to be removed. Taking the oil pan off will help you find any pieces, and also allow you to seal it up so no more leaks occur. You'll need gaskets for water pump, timing cover, oil pan, as well as timing components. Changing the components is confusing the first time, because you also have the jackshaft chain and sprocket involved. Having the motor at TDC on cyl #1 is very important when changing gears and chains. The service manual has a very good illustration of the way everything lines up. Dean's chain has no masterlink, and works very well. Pay attention, and don't move anything, and you will be okay. Pat

Like PAT said, you can do this, but there is a procedure and often a need to confirm that things are aligned properly. Again, we're happy to help guide you. You don't have to remove the head but IMHO you'll be so close, and with the possibility of damaging the gasket while removing the front cover, I'd just remove the head too. Yes, you would need new head bolts (I'd go studs).
What kind of compression numbers did you get? And how were they obtained? What did your spark plugs look like before you pulled the motor? Any oil burning that you know of? Reason I'm asking is that we're getting closer and closer to a rebuild and I know your plan was drive it fairly soon, and the cost is increasing! It may be OK to freshen it up if the valves and guides are ok... lap the valves and seats, clean up carbon on the head, replace stem seals... all within your ability I'd think.

Well Greg, let's get further into this can. While you have the oil pan off, pop a rod bearing cap and the middle main bearing cap, and check for wear. if you see copper or grooves, you can change them in the motor. You can also look at the cylinder walls from below to see if there is any damage or if the crosshatching is still there. I would not pull the head unless I was willing to rebuild it, as you said. Pat