Noisy Tappets?

[240paul]

Hi all,

Just a quickie,

I have adjusted the Valve clearances on my Z (8 & 10 cold) and still notice that when hot, the tappets are quite noisy - Not so when cold.

Is it just a trait of the L24 engine? - Or does thicker oil help??

Paul

[Alfadog]

I await an answer to this question too

[JEFF]

What oil do you use? Try adjusting them when they are hot.

In my manual the chart covers 1970 - 1981(non-turbo). The valve chart shows .01" for intake & .012" for exhaust ( HOT ) That would make .008" & .01" too tight when set cold. BUT.... the info that my manual shows would make your valves noisier. It would be easier to 'float' the valves if set at .008" & .01" cold. Are you sure the noise is in the valve train? If you are sure then use a screwdriver - touch it to the valve cover & put your ear on the handle - 'listen to the valves' move it over each section of valves when you hear the noise get louder that is where the problem is.

Recheck the valve clearances.

- Jeff

[240paul]

Jeff,

Thanks for the reply,

I did check the clearances "Hot" today and they were 010" & 012"

I believe that the engine has 10w-40 in it.

I did the old screwdriver trick as well just to be 100% sure and it is definitely the valve train - same amount of noise all the way along, but only when hot!

One thing I did notice is that although the head has a new cam & rockers in it, the little 3/8” round pads that sit on top of the valves (Terminology- Help!!) seem to be the original ones as they look as though they have about 5-10 thou of wear on them. Would be interesting to know if these can cause a problem.

Thanks

Paul

[2ManyZs]

Paul, the first thing I would do is check the wear pattern on the new rockers. If the old lash pads were used and were not the correct thickness, you could have the cam lobes running off the ends of the rocker contact area. This could be contributing to the noise you hear. Tha lash pad clearance could be off even though the rocker to cam lobe is adjusted correctly.

See this thread for a little more info...

http://www.classiczcars.com/forums/showthread.php?threadid=6342&perpage=15&highlight=Lash%20pads&pagenumber=2

[24OZ]

Hi Paul,

I am not clued up in this at all. But I do have a factory service manual and if you want me to photocopy you the relevant pages, let me know and I'll do so...

George.

[240paul]

That is interesting!

The Haynes manual says nothing about different size lash pads - (they call them rocker pads?)

Makes sense to me - the head had new seats put in for unleaded so I suppose there is a big chance that the tops of the valve are higher/lower than what was original.

I will have a look and see the wear pattern on the rocker (where the cam strikes) and report my findings.

George,

Thanks for you kind offer Does the factory workshop manual go into detail about different size lash pads??

Thanks

Paul

[240paul]

I have just taken one of the rockers out and a lash pad. The contact area on the rocker looks too far toward the pivot post?? – The wear on the lash pad can’t help the situation either I suppose!

(See picture)

Paul

[JEFF]

Bingo!

- Jeff

[2ManyZs]

Yup, hate to say it Paul, but you will definately be needing thicker lash pads. More than likely all the rockers are going to look very similar to that one.:disappoin

[24OZ]

Paul,

I checked through the FSM and it doesn't really go into much detail on different size lash pads . Keith I think you have an FSM? Would you agree, or have I managed to miss it somewhere?

[2ManyZs]

Well, the FSM doesn't go into much detail about the lash pads.

You would be much further ahead to either have a good machine shop do the work, or if you choose to do it yourself, you really ought to buy one of 2 books. Either the book, "How to Rebuild Your Nissan/Datsun OHC Engine", or the "How to Hotrod and Race your Datsun".

The How to Rebuild book goes into pretty good detail on how to measure, and how to determine if the wear pattern is correct.

You might also want to make good friends with someone at a dealership or shop if you are going to do this on your own, as you might need more than one set of lash pads so you can determine the exact thickness you need. They are a bit pricey and there are quite a few different thicknesses available... If you look at the thread I posted the link to you'll see what I mean. Perhaps if you found a shop that has the lash pads, you could make a deal to return the unused ones and only be charged for the ones you need after you measure and set up the lash pads on you head.

It would be a lot easier to do this while the head is on a workbench too, I know, but to do it on the engine in the car your gonna have to lean on the fender to get your measurements, and to be able to see the wear pattern on the rockers.....:disappoin

[240paul]

Thanks for all the info!

One thing I did notice is that all the inlet pivot posts are about 2 turns higher than the exhaust ones. And all the exhaust lash pads have a centralised wear pattern

The picture I posted was a rocker from an inlet valve.

Thinking about the valve train a bit deeper - am I right in saying that the pivot post retaining spring actually keeps the rockers against the profile of the cam at all times? - So any actual noise would be due to the gap of the rocker arm where it sits on the lash pad?

I am just trying to work out from an engineers POV where the noise is coming from. On the other thread it went into detail regarding lash pad height affecting the valve timing to which I understand. But if the clearances were the same regardless of what size lash pad, why would there be more noise?

Thanks

Paul

[240paul]

From http://www.courtesyparts.com/

.180" Lash Pad (1 pad) (12 Required)

Code: 99996-M1180(S30)

Price: $3.00

I know I will have to check for the right sizes but are these the right type??

Paul

[24OZ]

Paul,

I have both those books Keith suggested and I hadn't thought of checking them :stupid: .

Both books go into pretty good detail on the lash pads and sizes.. I can phocopy you the relevant pages, once I get back to work, on Wednesday.. Let me know if you want me to do this and I will mail them to you, courtesy of works franking machine .

G.

[2ManyZs]

Those are the right type, you only need to find out for sure what thickness you need. I think I read that the stock ones were ~.120 or there abouts.....

I'd say that the majority of the noises you are hearing are coming from the valves slamming shut. If you think about it, the cam lobe is running off the rocker and the valve is then slamming shut, instead of having the cam lobe close it slowly, which is your duration of the cam.

It doesn't surprise me that some of the rockers seem OK while other are not, all due to the differences in valve stem lenght, however minute. Somewhere along the way perhaps some of the valves were replaced with aftermarket valves which were just a bit off the factory specs...

[240paul]

George,

Thanks for the offer - that will be greatly appreciated :classic:

Keith,

Seeing that the rockers are new and the lash pads have wear on them - the new rockers are beginning to wear into the "wear" of the old lash pads, I will try replacing all of the lash pads as this is a cheap and easy thing to do.

On the noise issue you was talking about - would there really be a difference between hot and cold?

Will let everyone know what the outcome is!!

Paul

[2ManyZs]

Doubt if hot or cold would make much difference in the noise since it's not really a clearance issue. It's more of a valve closing issue that is making a lot of the noise since they are closing too rapidly because the cam lobe is running off the end of the rocker like that.

Once you get this straightened out, I'd say the performance of the car ought to increase since you are not getting near the proper duration of the cam and only half the valves are truly in time with the engine.

[ZXatlast]

Greetings Guys!

I am a just brand new, and first time 1979 280ZX owner. It's taken a while, but I'm 'here' now. New to Z's altogether, really. And just now joined this forum too, so I'm still finding my way about.

A simple question, I hope, if I may.... The bloke I bought it from spent over a grand and a half having the head reconditioned for its still-in-place original L28e engine. All well and good. However, the tappets -- is that a term you use? I'm referring to valve clearance -- are a bit noisy. I am quite happy to get in there and make the adjustments as a first step (I say "first step" because I am hoping I'm not going to get the other issues being discussed here).

However, adjusting those clearances, according to the factory manual, requires a special tool I didn't notice any of you referring to that tool, so I'm hoping it isn't needed. And I haven't taken the rocker cover off yet, which might make the answer to my question visually obvious, but, since I'm here, my question is, is that special tool mandatory? Just judging from the not-at-all-detailed pics in the manual, you should be able to do the same thing by manipulating an appropriately-sized standard spanner into the right place.

I would be very grateful for advice....

All the best,

Steve

[Diseazd]

zXatlast.......The special tool is a simple feeler gauge. If the bloke that had the head built had the work done at a reputable rebuilder, the rocker geometry (centering the wipe pattern) will have already been done. If not, you'll need to make sure that it is set up properly or you'll experience the same problem as above. Find out who did the work and if rocker geometry was set up. if it wasn't, you're in for a learning experience. Welcome to our fraternity! Guy

[ZXatlast]

Thank you Diseazd, very much.

With great respect, though, the pic in the manual isn't overly informative; I've just gone back to the manual and it refers to a "Pivot Adjuster ST10640001". It is seemingly a torque wrench looking device and where you'd attach a socket it has a long-ish arrangement that ultimately fits around the pivot.

Now, I haven't yet seen these pivots in the metal, so if they have a 'normal' hex-shaped surface to adjust them by, for instance, then all will be fine. But if the place you grab to adjust them is some strange other shape that a spanner never fits, then it becomes more, umm, interesting.

But as I said, you guys never refer to it, so I'm hoping that the special tool just makes it easier than manipulating a standard spanner in there.

Just for the record, it states that the clearances - adjusted hot, and it says operating temp hot(!!), as opposed to warm - is 0.25mm inlet and 0.30mm exhaust.

And thank you for your welcome, I hope it'll be productive both ways. When I get my profile done, obviously I'll put a picture of my 280ZX up in it's current condition, which is pretty damn good for a $2250 outlay; fully usable and rego-ed til May.

All the best,

Steve

[Diseazd]

Steve.......Pick a valve....any valve......turn the engine over where the lobe is straight up.......now with two open end wrenches, loosen the two locking nuts securing the pivot ball. I believe one is a 17 mm and one is a 14 or 15 mm open end wrench. Once you loosen the two lock nuts you can turn the pivot ball up or down to adjuct the clearance between the rocker and the heel of the cam lobe. You check by sliding a feeler gauge between the rocker and the heel of the cam lobe. Clearance should be .008 intake and .010 exhaust at cool temps. It ain't rocket science. Once you get the clearance right,you lock the two nuts together....but continue checking as you tighten them down because they change as you tighten them. Play around with it....you'll soon get the hang of it. Good luck.....looking forward to seeing your Z. Guy

[jmortensen]

Pop an intake and an exhaust rocker off. Clean it and use a marker to color the friction surface black (don't know if you have Sharpies down under, but that's what I used). Reinstall the rocker, adjust the valve, and turn the engine over a couple times. Look at the pad on the rocker, and you can see if the wipe pattern is centered. If it is not centered, sacrifice a feeler gauge. Cut it into strips and use it like a shim between the lash pad and the rocker. When you get it to the right thickness, your wipe pattern will be centered. Add the thickness of the shim stack to the thickness of the stock pad, and then you know what size lash pads you need so you don't need to order extras. Some engines take a different pad on intake and exhaust, but if your machine work was done correctly, all of the intakes should take the same size lash pad, and all of the exhausts should take the same size lash pad.

It's time consuming, but not difficult to figure out. Some people will say to do the marker test with machinist's blue, I like the market better because it doesn't smear as much.

LOTS of info on this over at hybridz.org. That's where the cutting the feeler gauge tip comes from.

Edited February 21, 2011 by jmortensen

[Diseazd]

Jon.....I think you're way over his head......this is his first Z......one baby step at a time!

[ZXatlast]

Guy and Jon, thank you very much indeed. I do appreciate your concern Guy, seriously. Obviously I gave the impression of a 19year old with his first 'proper' car, but no...

I'm not a novice, I'm a novice to Z's, but hardly my first car/engine. Before the Z there was the fully blue-printed BMW 4cyl sohc (gas-flowed, crack tested, everything oversized, 324degree monster cam, balanced to 1/1000th gram, etc., etc.) and the Rover V8. Concurrent with this Z is a Mercedes V8 and a Toyota (Le Mans homologated) 3S-GTE. God! I love that engine!! But I digress. The BMW 2002 and the Celica are going to be my extreme interpretations of street-going Le Mans racers. The Mercedes V8 and the 280ZX are more traditional, if that's the word, customising projects, the Rover P6B a little less so, but mainly in the engine.

I am more than capable of designing an engine from scratch, starting with the castings; I just can't imagine why I'd bother when there's so much brilliant stuff already out there just 'needing' the appropriate (re)design tweaks.

What I came here for, was to get ahead of the game in the sense of not falling into unexpected quirks that novices to this specific stuff might fall into. And both you have spent time and effort, with gentle consideration for a new member, and have ensured I wont. So to both of you, again, thank you very much, it is much appreciated.

If it helps to understand my approach, I am a Research Analyst often by profession and by 'natural bent'. So I like to gather as much data on something new before I get 'dirty up to my elbows'. As opposed to a very good mate of mine who'll jump in and tweak and pull and take apart without any research up front. He often gets stuff done quicker than I do, but he sometimes breaks a few things along the way, which he then has to fix, and that isn't my natural way.

Now, since you gentlemen have been so generous and forthcoming, perhaps I could get into a more interesting question...? I want to make the L28e 'right' so I can experience the 280ZX in its original intended form. It's about getting a sense of the car's character and a feel for the overall engineering quality and the 1979 'design intention'. This is discerned as much through the senses in the seat of my pants as it is through the logical engineering I can eye-ball.

But even now, after this short time, I can see I wont be satisfied. So I've been playing with ideas. My first thought was that with 8.3:1 compression the L28e has to be perfect for some simple but effective non-radical supercharging. I'm still researching, but the time and agro and cost involved seems a bit counter productive when compared to another option that seems readily available; more or less.

OK, the first thing is to point out is that I acknowledge the 'boulevard cruiser' and 'soft GT' design of the 280ZX. That is exactly what I like about it and why I wanted it and what I want to retain. I don't have an intention of turning this into my third interpretation of a Le Mans street-legal racer. I want to fill that GT-flavoured space with this 280ZX, I don't have another car that does. The limousine-sized Mercedes is sort of on the border but it isn't the same concept really. However, I do want to take it further towards the boundary that once crossed it becomes a racer -- approach the boundary, not cross it.

Which brings us, perhaps, to the most logical, and apparently cheapest option. And that is to replace the L28e and 3-speed auto with an RB20DET and 5-speed auto. Now, all that background was to bring us to this question: So far I have gotten the (hopefully true) impression that unbolting the L28e and 3-speed and then bolting in an RB20DET and 5-speed is a relatively straight forward process. I'm not talking about the engineering required to make it all work, these things I understand already, and what I don't, I'll find out. What I'm asking you about is the physical fit. Apart from reworking the positions of ancillary components, in terms of specifically the engine lump and attached box, is it an easy refit? Apparently, even the tail/propeller shaft bolts straight up, I'm told. But, I'm asking you guys for confirmation, or not, as the case may be.

The ultimate point of this research question is that if I have to cut and weld in a chassis to make it fit (I'm sure that isn't needed, that was a worst case conceptual example), then obviously I'd go looking for the next best option. I'd like to stick with Nissan rather than the apparently common Chevy small block, which also, apparently, slips in easily. Someone else's engine makes it not a Nissan anymore, and I do want to retain the Datsun/Nissan flavour, so the RB20DET is my current favourite.

Oh! One more thing, if I may? Do you guys know how big a wheel tyre combination I can fit and with what offsets and still fit within the standard guards? I can fiddle and find out, but it strikes me that this is stuff you guys would know off the top of your heads.

AND... another one, but more engineering critical: Can I re-torque the head bolts to the assembly specs with the engine hot? Or do I have to leave it to cool down first? I've never worked with hot engines for these processes in the way the factory manual for the L28 sometimes specifies; the 'Euro gear' I'm into is always specified cold.

OK, that's probably a big enough mail for now, and on the assumption that you're still reading this, thank you for that too.

All the best,

Steve