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Stock valve spring "Coil Bind Height"?

kumfasa

Well-known member
Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Hi All,
Have googled and searched to no avail. Does anyone know at what height the stock Valve spring binds at?
 

prove_it

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Joined
Jul 3, 2008
Messages
4,201
Location
Sioux Falls, SD
Easy, don't run stock valve springs. If they have over 30k miles they have already weakened. Over 100k miles and they will have less than have the closing force as new.

Stock springs are horribly weak. Don't bother checking them and just get new springs.
 

kumfasa

Well-known member
Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Thanks,
I understand the deficiencies of the stock springs over time and if I was to rebuild this head for the purpose of producing more power I would buy some aftermarket springs. But I just want to get this thing back together and running with the possibility of building a better prepared engine to be swapped in later. I miss driving it and don't have the funds to do it the right way at this time.

My thought was to shim the stock springs to increase the valve seat pressure and offset some of the loss in tension from their life so far. But I obviously don't want to shim them to the point of binding. Hence my question.

I just squashed one in my vice and got a bind height of 1.102. Does this sound right? Have I measured this correctly? Is there another method?
 

prove_it

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Joined
Jul 3, 2008
Messages
4,201
Location
Sioux Falls, SD
DO NOT SHIM UP THE VALVE SPRINGS!!!!!!!!!!!!!!!

Very bad. If you can swing $100 bucks for springs then you need to work harder. Don't cheap out and whine later when the valves are bent.
 

kumfasa

Well-known member
Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
THANKS FOR THE ADVICE RYAN!!!!!
And tectic I have read as many post as I can find from BogusSVO here and on DSMTuners. He's a good man and provides great info, I would welcome him to chime in on this post.

I get that the stock springs lose tension over time. I also understand that shimming valve springs is one of the most common and preferred methods for achieving adequate seat pressure and installed height at machine shops. So saying that it is "very bad" without qualifying it doesn't mean much.

I have measured my valve springs and get a free height of 1.878, with the FSM listing 1.866 as the service limit and 1.906 as the factory spec.

Based on my installed height of 1.575, the stock cam lift of .252 and the coil bind that I measured of 1.115 this leaves .208 of free spring travel at full lift. I could use a .030 shim and still have .178 of free spring travel before coil bind. adding .030 on my 1.878 free height would put me at 1.908 free height which is bang on spec and should equate to better seat pressure without the risk of coil bind.

Am I missing something? Why is this "very bad"?
 

prove_it

Well-known member
Joined
Jul 3, 2008
Messages
4,201
Location
Sioux Falls, SD

tektic

Well-known member
Joined
Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
What you said was true, however if your reving heigher using more boost or using different cams than factory, your going to run the risk of valve float.

If you want to change springs after the engine is assembled it will cost more in gaskets than the springs I linked cost. That's if labor is free.
 

kumfasa

Well-known member
Joined
Feb 28, 2015
Messages
125
Location
Tauranga, New Zealand
Not sure if you care but thought I would let you know. I've decided to go with the BC1100 valve springs. This choice came about after putting in many hours of porting and polishing work on the head, it would be a shame to increase boost and lose that benefit due to soft springs.

There was also a key calculation I left out of my previous post which is the rocker arm ratio (1.7?) which actually leaves very little room for shimming the stock spring before hitting coil bind.

Thanks for your input.
 
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