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Old 07-08-2012, 03:20 PM   #1
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Wink Single or Dual valve springs for the 1.8 BP??

I'm in the process of searching for what valvetrain components I want to use, and I have a simple question.

Single or Dual valve springs? This is for a boost application with a goal of 350whp

Also...are the BPs Interference engines?

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Old 07-08-2012, 06:04 PM   #2
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Seems thee hot set up is dual springs.

Spring pressure needs to be set for the cams tho.
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Old 07-08-2012, 06:13 PM   #3
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I went with a slightly stiffer single Supertech spring that I got from 949 just in case I over-rev, since I was rebuilding a head.
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Old 07-08-2012, 06:26 PM   #4
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Old 07-08-2012, 06:57 PM   #5
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I will start with the stock cams, but I intend to upgrade to bigger cams. So for a dual spring I assume would cause more pressure and wear with the stock cam application?

And 949 so far does seem to have the cheapest single springs for supertech
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Old 07-08-2012, 07:50 PM   #6
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Double or single springs don't mean ----. It's all about spring tension at seat and fully open, material and shape, coil bind height. Those will differ depending on what you want.
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Old 07-08-2012, 10:04 PM   #7
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I like double springs for 2 reason. You have a small safety net if one fails (not as important in our cars since they are not interference without some meaty pistons and/or cams), and they help cancel out harmonics that can cause valve float, because you can float the valves before the spring is actually insufficient if you hit a harmonic.

Of course you can get the second effect with less weight if you use bee hive springs or conical springs and those have the advantage of being lighter than a dual setup and also allowing more lift since they coil bind at a lower height than straight springs.
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Old 07-08-2012, 10:18 PM   #8
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Quote:
Originally Posted by Leafy View Post
I like double springs for 2 reason. You have a small safety net if one fails (not as important in our cars since they are not interference without some meaty pistons and/or cams),
Our engines are so incredibly "non-interference" that I bent all of my intake valves and never knew it.
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Old 07-08-2012, 11:37 PM   #9
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This is the set I'm currently looking at.

Supertech SPRK-1012-M18D Dual Valve Springs Kit Miata BP 164 lbs

Im just having trouble now deciding how stiff I want them.

Too stiff?
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Old 07-09-2012, 07:51 AM   #10
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You can calculate how stiff you need them to be based off your cam profile and your valve train weights. I dont know any real rules of thumbs for it though besides actually doing the math out, or putting it in this program called dynacam.
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