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

I await an answer to this question too

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

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

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

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.

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

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

Bingo!

- Jeff

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

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?

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

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