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Long story - don't know how to keep it short.

This is the second time it's happened to me. The engine has just been rebuilt. I haven't driven the car on the road yet. Less than 5 minutes on engine. The head was put back together by the engine shop. I just adjusted the valves

Here's the story,

One Month ago: I adjusted the valves cold to spec and then she ran beautifully for several minutes. Shut down, came back next day and started again for a few minutes, ran rough. shut down, came back next day started, ran rough I took up to 3,000 rpm and Clangk, clunk, pop, tack, tack... shut down immediately (talk about a sinking feeling). Turns out 3 of the shims had popped out of their sockets on top of the valve stems. I put them back in (nothing looked damaged) and had a mechanic friend adjust them for me. He is the Z king and said nothing was damaged. The car ran beautifully for several minutes. I shut her down but didn't adjust the valves warm.

I didn't start the car for the entire month because of leaking injectors.

Two days ago:
I finally replaced the 3 leaking injectors and started the car up again. Ran rough but I thought it was the injectors. I shut her down. 2 hours later I came back out and cranked the engine. Right when she started I got that same Clack, tack, tack and I shut down immediately. I pulled the valve cover and one of the shims was half out of it's socket again! @#%^&*^%*(&**&^@#

I think that the problem is that I haven't ever adjusted the valves hot. I kept starting and stopping the engine for real short periods of time. and didn't give the shims time to seat properly. The cam, rockers and shims are from this engine but there is very little prior wear on them. All rockers were matched to the proper cam lobes when I put it back together.

Does anyone have prior experience with this problem? What did I do wrong?
 

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Re: 78Z -shims popping out from under rockers!!! H

Hey,
I just wanted to say that your web site looks pretty good and that it looks as if that car of yours is coming along very nicely. I hope you fingure out the problem with the valves. Keep up the good work.
Joshua L.
 

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Re: 78Z -shims popping out from under rockers!!! H

> Does anyone have prior experience with this
> problem? What did I do wrong?

Sounds like you're just not giving everything a chance to wear and seat. That is why they recommend running at 2500-3000rpm for 10-15 minutes when first starting a new engine. It gives the metal time to expand and this is when wear starts to occur to seat the rings/valves/cam etc... I think it is just a matter of getting the valves adjusted hot. They tend to stay in spec for much longer that way. The things on top of the valves that keeping popping out are called lash pads, and they come in different thicknesses.
One a side note, is that an original cam you're using. If not, you may have a valve geometry problem going on. You need the cam lobe to make contact with the rocker pad at just the right time, so that none of the cam is rubbing on the end of the lash pad. This can be corrected with different thickness lash pads. You might also want to verify that all you're rocker arm adjustment screws are fully tightened.
By the way, the website looks great, and you're conversion is quite impressive. Don't worry, I'm sure you'll get it all sorted out.
 

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Re: 78Z -shims popping out from under rockers!!! H

> Sounds like you're just not giving
> everything a chance to wear and seat. That
> is why they recommend running at
> 2500-3000rpm for 10-15 minutes when first
> starting a new engine. It gives the metal
> time to expand and this is when wear starts
> to occur to seat the rings/valves/cam etc...
> I think it is just a matter of getting the
> valves adjusted hot. They tend to stay in
> spec for much longer that way. The things on
> top of the valves that keeping popping out
> are called lash pads, and they come in
> different thicknesses.
> One a side note, is that an original cam
> you're using. If not, you may have a valve
> geometry problem going on. You need the cam
> lobe to make contact with the rocker pad at
> just the right time, so that none of the cam
> is rubbing on the end of the lash pad. This
> can be corrected with different thickness
> lash pads. You might also want to verify
> that all you're rocker arm adjustment screws
> are fully tightened.
> By the way, the website looks great, and
> you're conversion is quite impressive. Don't
> worry, I'm sure you'll get it all sorted
> out.

STEVE, The same thing happened to me but it only happened above 7500 rpm and only on one valve but it is possible you have the same problem.MY problem was spring load tension.My solution was to install two shims underneath the #5 intake valve spring instead of one.I drag race my 240z and since doing this I have not had any more problems with the lash pad popping out.It is possible that your valves are sunk in seats or that your valve spring retainers have warped wider at the keepers allowing the spring to have to much installed height.On my car it was the retainer that was alittle to wide at the keeper and it had raised retainer height aprox .030 inch.I could have just as easily replaced the retainer but it was late and I needed a quick fix and it has worked fine for five months now.Hope this helps. Norm in N.C.
 
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