Don't get me wrong. I'm not trying to throw the engine builder under the bus. I'm just trying to make sure I understood what happened. Mistakes happen.

So, why don't you just use stock spring retainers? Is there something different about the tops of the Isky springs that makes them incompatible with the stock retainers? Or is there something way better about the Isky retainers that make them a better choice over stock? It's not like people are complaining all over the internets that the stock retainers are inferior. I've never heard of a failure. Ever.

Or you're thinking that since you paid for them, dad-gummit, you're gonna use em!!  I mean if that's it, I get it!      Haha!!

10 hours ago, Captain Obvious said:

So, why don't you just use stock spring retainers? Is there something different about the tops of the Isky springs that makes them incompatible with the stock retainers? Or is there something way better about the Isky retainers that make them a better choice over stock? It's not like people are complaining all over the internets that the stock retainers are inferior. I've never heard of a failure. Ever.

I do not know offhand if the Isky retainers and the stock retainers are the same on the underside.  They might be.  I think that swapping to the stock retainers will alter the installed heights because the keepers lock in a different location relative to the spring seats.  I will explore the possibility of using them this weekend when I pull off the Isky retainers.

As long as the springs are compatible with the retainer disk, then I don't think any of the rest of that matters. The tip of the valve will be in the same location regardless if there is a change in exactly where the keepers lock onto the valve stem. In other words...

The height of the valve stem tip above the head is dictated by the location of the valve seat (inside the cylinder) and the length of the stem. And since the lash pad sits on the top of the valve stem tip, neither the location of the keepers or the location of the notch in the stem for the keepers would have any effect on the installed height.

Unless I'm misunderstanding "installed height" or something?

While it is true that the tip of the valve is going to be in the same location... and the lash pad will sit on top of that in the same location, the location of the upper spring perch is different between the stock and the Isky retainers.  Therefore, just swapping out the retainer to a stock one is going to to change the location of the upper spring perch and the installed pressure of the springs.  It may be possible to remove or add shims.  I will have to investigate more closely.

Here is a link and brief description of the retainers I bought.  
Chrome moly valve spring retainer set
"Made in the USA by Isky cams. These will fit Datsun L series engines found in the 240Z, 260Z and 280Z. High quality parts made for racing or street use. Includes 12 retainers.  These retainers will alter the installed height, for use with Isky high pressure springs PT# 800-1374."

Gotcha. So "installed height" has nothing to do with the location of the tip of the valve stem. Seems important for valve pressure and bind analysis, but really doesn't have anything to do with the problem you're having.

So I poked around a couple seconds and turned up a thread on ratsun that talks some about the isky retainers. Seems the Isky retainers are specially made to work with Isky springs? Something about fewer coils maybe and keeping them centered?

But there's also talk about making sure you don't sink a seat, and people have had the same tall retainer problem and have cut down the retainers:

https://ratsun.net/topic/42818-l20b-with-a87-head-valve-spring-questions/

 

Edited September 21, 2024Sep 21 by Captain Obvious
more detail

And while I'm here, I've got a question. You said you were going to pull off the Isky retainers this weekend...

What keeps the valves from dropping after you remove the retainers? Rope or compressed air in the cylinder to get the retainers off and then some kind of clamp or feature attached to the stems after you pull the springs off? Maybe temporarily install stock retainers?

Just curious, but what's the plan?

1 hour ago, Captain Obvious said:

Just curious, but what's the plan?

I plan to use zip ties to around the stems to hold them up.  I will rotate the engine to top dead center for each cylinder and use a leak down tester to input the compressed air.  That will allow me to remove the spring retainer.  Then I will put zip ties around the valve stem at the valve seal.  This should keep the valve from dropping while I rotate the engine to the next one.  I will need to do that for all six exhaust valves.

Edited September 21, 2024Sep 21 by inline6

Recently, I sent off a small box of hardware for plating.  Unknown to me, the place I sent the parts to had gone out of business, and my box got hung up in the UPS/USPS system for quite a while.  But, I was successful in getting the box of parts back finally, after many weeks.  I found another plater, and sent the parts off again.  He got them done literally over a weekend and got them back to me already.  

For the horns, the first plater I sent them to wouldn't do them.  So, this time, I drilled out the rivets holding the electrical parts to the back plate and sent the back plates off for re-plating.  I had to order "semi-tubular" rivets and "rivet curling punches" to set the new rivets.  Today I experimented a bit with those.

  

The rivets for the "bridge bar" need a bit more work, I think:

  

The rivet for the spade connector looks perfect:

  

 

Didn't have much time to work on them tonight, but should be able finish them up this weekend.

 

 

 

Edited September 21, 2024Sep 21 by inline6

10 hours ago, inline6 said:

I plan to use zip ties to around the stems to hold them up.  I will rotate the engine to top dead center for each cylinder and use a leak down tester to input the compressed air.

Cool. Sounds like a plan. Hope the retainer shortening takes care of the issues you are having and that's the last hiccup!  

14 hours ago, inline6 said:

Recently, I sent off a small box of hardware for plating.  Unknown to me, the place I sent the parts to had gone out of business, and my box got hung up in the UPS/USPS system for quite a while.  But, I was successful in getting the box of parts back finally, after many weeks.  I found another plater, and sent the parts off again.  He got them done literally over a weekend and got them back to me already.  

For the horns, the first plater I sent them to wouldn't do them.  So, this time, I drilled out the rivets holding the electrical parts to the back plate and sent the back plates off for re-plating.  I had to order "semi-tubular" rivets and "rivet curling punches" to set the new rivets.  Today I experimented a bit with those.

  

The rivets for the "bridge bar" need a bit more work, I think:

  

The rivet for the spade connector looks perfect:

  

 

Didn't have much time to work on them tonight, but should be able finish them up this weekend.

 

 

 

links to the rivets you bought and tools?

Tools:

 

 

Rivets: note diameter and length.

 

I can send you some rivets as I have many to spare.  

 

 

Anyone have a 240z horn they'd be willing to part with for cheap?  I need one to cannibalize from.