Datsun L-Series Engine Testing and Tuning Ep.4 Adjusting Cam/Valve Timing (SEE COMMENTS)
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- Опубликовано: 5 фев 2025
- Now that we have the valve cover open, we'll show you how to adjust the valve timing and compensate for timing chain stretch by utilizing the different camshaft positioning.
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If you can, turn the engine by the crankshaft bolt instead of turning it by the camshaft bolt like I'm doing here. The important thing is that the marker on the crankshaft pulley is exactly at 0, so either method should work. However, turning the engine by the crank "simulates" how the timing chain actually gets pulled, so it may be more of a precise method.
Getting a bit more into detail, turning the engine by the camshaft bolt creates a slack on the right side of the chain (facing the engine), and turning the engine by the crankshaft bolt creates a slack on the left side of the chain, which may minutely impact the reading of the camshaft timing. However, this discrepancy should be minimal given that the timing chain tensioner is working properly. After shooting this video, I checked the timing again by turning the engine by the crank this time, and the timing was exactly the same so I don't think it matters too much, but the preferred method should be turning by the crank.
In any case, whenever you adjust the valve timing, conduct a compression test and go for a test drive. If it has trouble idling or running smoothly afterwards, chances are you need to readjust the timing.
Another interesting tidbit that I didn't note in the video. As the timing chain stretches over time, the cam timing becomes increasingly delayed, and this effectively moves the power band upward. Unless you're racing the car (in that case this is preferred since the engine is always at higher RPMs), this is not recommended since this also results in an overall loss of power. I also think I speak for most Datsun Z owners when I say, we could use a bit more accessible torque at low RPMs.
On the other hand, advancing the valve timing too much will raise compression and can lead to pinging/pre-ignition detonation, necessitating the use of higher octane fuel.
Excellent real-life video. I am just about to check the chain tension, and this is so clear
Nice video, I've been working on these engines for years but it's nice to see a video on what is in the manuals. An adjustable cam sprocket would be nice to dial in the perfect timing, and a new chain is probably not bad insurance too.
All these details make a difference to engine output. And it's fun doing it on these old engines because most of the stuff is so accessible.
You can change the lobe separation angle on Datsuns with different sized lash caps on exhaust and inlet. We also ground the cam wipe pad on the rocker flat to increase valve acceleration, effectively making it a cam with longer duration, its a old ford 2L trick.
Thanks for these videos. I am probably going to have to crack open an old L16 and this is immensely helpful.
The most common as well as the most overlooked cause for the v notch on the camshaft sprocket sitting to the left of the alignment mark when the crankshafr/piston is at top dead center is due to the amount of material that gets removed from the bottom side of the cylinder head when it gets cut down to flatten any wattage of the gasket mating surface. The sprockets are the other less common culprits. A tiny bit of wear in the chain rollervalleys decreases the sprocket diameter which also retards camshaft position. The timing chain is rarely the culprit but it always takes the bullet
So happy you're doing this bro! Much love and positive vibes your way!
Haha I actually really thought it was going to be dead on, and I was just going to show you guys what well adjusted timing looked like. I didn't realize my timing chain was so stretched, but I guess it's good that we checked!
Hello, I been following your videos for years now, and I'm finally at this point on my project 280Z. My issue is that the crank pulley notch is at the mark before 0. However, the camshaft is at TDC, and the pistons are all positioned correctly. I had just installed a rebuilt head. Another thing I'm seeing is that the camshaft sprocket dials aren't even coming close to the bright link, could this be caused by the fact my crank timing is off? And if so, could I temporarily install my sprocket back on to rotate the crank to get it to 0 TDC?
interested in seeing how this effects compression and vacuum readings. fyi, the FSM has that torque at 94-108.one more thing, did you follow the advice about setting TDC by only rotating crank on direction (if you overshoot you have to go around again rather than backing up?) to keep the chain tensioned before reading the marks? I have never checked this before on mine, so glad you did this video.
These are really good questions, appreciate you tossing them out. I hope other viewers see these as well.
I don't know about the vacuum, but advancing the cam timing definitely increased compression by around 5 to 10 PSI. I did a quick compression test after adjustment, and now I'm getting on average 177 across all cylinders, give or take 3. I'll post a detailed compression testing video in a later episode.
Haha yes, I should've checked the FSM for the "tie-breaker" (it actually should just be the only source for stuff like this). It's good to know the torque rating the FSM recommends, I'll be sure to go back and retorque the bolt.
Yes, the engine should only turn clockwise (facing the engine). If you need to go back for whatever reason, OVERCORRECT and rotate the engine clockwise back to wherever you need to.
Also, I pinned another comment in the section discussing this, but one thing that I should've mentioned was that it's preferred that you turn the engine by the crank (i.e. not the camshaft) since this more accurately simulates how the chain actually gets pulled.
Where do I buy that timing chain holding tool?
Wow....I was LOVING this video until the camera drifted off scene at exactly what I was trying to see. The position 1,2, 3 thing has me totally confused. My timing gear has the numbers like 90 degrees off from each other and I just don't get how I'm supposed to move the gear that far. Thanks for the effort but that was a bit frustrating.
EDIT- After some net searching....I get it now. Each number on the gear has a different locating pin hole. Pin is on the end of the camshaft. Hold chain in place while walking the gear around to the next number's locating pin hole. I was picturing a keyway type deal which would need three grooves in the gear instead of three pin holes. Thanks!
what is the dimensions of the timing chain wedge? they are sold out online. need to make my own. thx
When adjusting the sprocket does the chain need to adjust as well or do I just rotate the sprocket to the next position? Also do you know if anyone has an existing file to 3D print the blue spacer you used for the timing chain?
Those plugs were torqued way too tight. It shouldn't take a breaker bar and that kind of force to get them loose.
Dude..¡awesome channel!
If you don’t mind me asking, what engine is that exactly?
I’m inquiring because I’ve an L20b I’m working on 😍
L28E!
I'm going to repair a L18
Think thats going to make a huge difference. Where did you buy the blue chain holder?
Hey Charles, it's a gem that I found on Amazon. So glad I didn't have to carve one out of wood! www.amazon.com/Alltrade-648831-Nissan-Timing-Holding/dp/B0002Q8TV4
I inadvertently made that hell of a mistake. :|
I used a push block to hold tension but it was no match for the tensioner
I managed to hold it in place with a screwdriver and remount the cam sprocket and chain
However The car is now hesitating and misfiring at any rpm when given more than 40% throttle or so
Almost as if it’s lacking fuel But I don’t believe it is.
Could this be a timing problem?
Just a note, I know this is an old video. Be very careful tapping on the sprocket and dowel that goes into cam. You can crack the cam by putting too much pressure on the dowel. I know this from experience...
You've done this a dozen times, and then one day you do the unforgiveable and leave the tensioner wedge in place. You set the cam, reassemble the engine, start it (no need to turn it over, you've done this a dozen times, didn't you say) and see the front of the rocker cover erupt as the wedge gets driven up thru it, lifting the chain off the sprocket. You slowly realise the damage you've done (yeah, bent valves and all) push the car into the garage , and go pour yourself a drink stiff enough to kill the pain of anguish.
Oh and that error in the manual he mentions? (the 40fp cam sprocket bolt torque instead of 100fp? yep, that's good for another bunch of bent valves when the sprocket falls off 20 miles from nowhere, trust me on this.
Listen and learn grasshopper, so that my pain might save yours!
You must have been working at night with min. light or to many stiff drinks as you say.
Have you heard of a camera mount?
Hi and thank you for this (and all the other) video(s).
I'm in the middle of fixing my timing chain rattling noise and you answered my remaining questions I had from just reading the books.
Thank your very much for your effort of sharing your knowlegde - it's very much appriciated!!
The only thing I'm still struggeling with is the correct way of turning/adjusting the crankshaft.
By turning at the crankshaft bolt I create quite a big slack on the RH side (looking from the front) and I'm not sure if this makes the reading unprecise.
My theory is, that the tensioner is getting compressed a bit while turning the crank at the crank shaft bolt.
This could lead to a more advanced (or "less retarded") reading than it actually is - what do you think?
You're right, this confused me a lot as well. I think you mean the left hand side? You should turn the crankshaft clockwise facing the engine, which should create slack on the left (part of the chain going from the crank to the cam sprocket). This is the position at which the cam should be timed, but as you adjust the sprocket or chain, it might be a bit imperfect because of the slack. What I did was I turned the crank clockwise again after adjustment until everything was back in position. This allows you to account for the slack and check the timing one last time before putting the cover back on.
I interpreted the drawings in the manuals differently, assuming they were exaggerated to clearly show which side of the notch you want the groove and as long as you were on one side you were fine. I didn't interpret overlap between the notch and groove to be an issue. I thought you'd be okay at position 1 and definitely okay at 2. If I'm wrong about that, then my timing is retarded. Hope you do a test drive right after this and a compression test to feel/see what the differences are.
Just saw your compression results. Awesome.
Ah. I think the drawings are quite literal. It actually says in some references that the left end of the sprocket notch should be to the right end of the groove.
Like I said in the video, the adjustments are very minute. I haven't taken it out for a test drive (we're covered in snow again), but I'll report back.
I agree the adjustments are very narrow, and learning this through experience conferred with my initial understanding of the drawings, that they were wildly exaggerated in the range they are displaying which is that of two extremes, one being extremely advanced and the other extremely retarded. That is, if the drawings were literal they wouldn't be so dramatic but more in accordance with the narrow range of adjustment this timing process provides. It follows that if the drawings were literal the drawing showing retarded timing could never be corrected by the minute adjustments from the process itself. So how is the drawing literal? I do have the FSM, Haynes, and Monroe's book at my g/f's if one of those three are the references you mentioned. Even if it said that the left end of the notch should be to the right of the groove, I don't see how this is mutually exclusive with some overlap. The left end of my notch was to the right of the groove - when considering the whole groove rather than just the edge of it. If a solid reference says "to the right of the right end of the groove", that would be different.
+heymisterderp ah. I see your point. I think the depiction of retarded timing can only really be achieved if you're at position number 1 And the timing chain is wildly stretched (or it's just installed wrong). I don't think it's something you can actually get if the sprocket is installed correctly and you keep yourself to the three designated sprocket position, given that the timing chain isn't stretched beyond saving.
The depiction of correct timing I think is to be taken literally. That being said, my car still ran OK on position 1 before the adjustment, so I don't think you have to be absolutely precise. In another words, you should be fine if there is little overlap, it's nothing to be too concerned about.
What I'm saying is, if you are actually adjusting the timing though, you should aim to have no or very little overlap.
Well all things considered it probably wouldn't hurt for me to try 3 too since my 2 is little better than yours. I'll wait for your test drive results though which might compel me to actually do it. Are you convinced that you got slightly higher compression readings from this adjustment or could those #s be reflecting something else you did like a valve lash adjustment?
Datsun
Timing
85 ft lbs on those plugs Ova heah
2:18 minor asianism slipped through
Factory Nissan L Series chains dont stretch, they wear. Chain guides are what one should inspect for cracks and wear. Only experience makes 1 a good instructor. Shop repair manual technicians are the worst mechanics in the field. Your unoriginal Chris Fix type uploads are borderline infringement right strikes imo. NEXT!