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dejan wrote:And what do they say about IN -FK87 end EX -FK10 @112 ,1600 Turbo 1,4s end double springs valve.

so67vw wrote:

dejan wrote:And what do they say about IN -FK87 end EX -FK10 @112 ,1600 Turbo 1,4s end double springs valve.

I'd say lots of RPM, not at all fun to drive on the street, and unless you have a serious bottom end, BOOOOOM.... If you are racing it with the right gears it could be kinda fun, but I personaly like have'n more CCs, drivable HP, lots of grunt, and still able to use pump gas... In the long run less cost with better results... That's just my opinion though... You do what you want and have as much fun with it as you can...

Wally wrote:Yeah, I call them n/a cams and they work very well in a boosted engine too.
Because you have a bit lower CR in a turbo engine, just don't get too crazy on duration

Wally wrote:No, certainly not. Turbo engines love overlap as much as n/a to some degee, large duration just gives even less respons down low as turbo engines run much less compression ratio, so take it easy on the wild side of the profile range, unless you build a drag race car.
Duration is not exactly the same as overlap btw.

Stripped66 wrote:

Type 4 Unleashed wrote: There are so many springs out there that you can get your over the nose pressure and still have .150" before coil bind, and your whole valve train will thank you for it not to mention your wallet.

This is absolutely the most stupid valve spring advice I've ever read. You would do yourself a favor to read up about "spring surge" (under damped spring harmonics). Excessive clearance to coil bind does not provide the harmonic damping the spring manufacturer intended and contributes to spring surge (and broken valve train parts).

Pick a valve spring based on the pressure you need on the seat and at full lift, that sets up within the range of installed heights you can accommodate (either using shims on the spring cup, or retainers and keepers that can offset your installed height), and run the manufacturer's suggest clearance to coil-bind. Do not pick a large spring like a K800 (which is good for 480+ lbs over the nose) and set it up with 0.150" clearance to coil-bind for 400 lbs over the nose. Yeah, it's cheap, but it's completely ignorant of the engineering that went into the spring; and while you might run it without valve train failure, for how long?


This isn't a new concept, but some of you need to open your eyes and learn something, instead of propagating dogma. If you want a good read, a recent tech article in HotRod Magazine provided a good summary: http://www.hotrod.com/techarticles/engi ... index.html

HotRod Mag wrote:Thinking has evolved on how much safety margin is needed. About 0.060 inch used to be the textbook minimum, with more OK and even desirable. That's still an acceptable standard for everyday performance use, but Massingill says that in some cases "0.060 has become the maximum rather than the minimum." Godbold notes that "from high-speed video and testing, it is clear that adjacent coils contact as you approach the valvetrain limiting speed. Hence, modern springs are designed to run near coil bind and use the coil-to-coil interaction for improved damping at or near max lift. This interaction is one of the most effective means of dampening spring surge, but the valve spring must be properly designed in terms of solid stress to safely use this interaction." Depending on the intended use, the spring and cam-lobe design, and the engine builder's preferences, you will now see coil bind safety margins vary from as low as 0.015 inch to as high as 0.120 inch, with tighter numbers predominating on very stiff valve trains. In a serious valve train, anything more than 0.150 inch can cause spring surge, which can greatly reduce the available spring load needed to close the valve.

There has also been several good discussions about spring surge on the speedtalk.com forums, with contributing comments by some of the best racing engine builders in the US.

The spring manufacturers were smart enough to specify the clearance to coil bind, and for a very good reason; don't be stupid enough to ignore their specifications and make up your own clearance.

Type 4 Unleashed wrote:

I thought I would post an update: There is currently a board member that is running a 2.2 ltr Turbo motor that puts out about 400 rwhp on the dyno. The relative engine components are as follows: WEB 163 with .500" valve lift, CB VW650 valve springs installed @ 1.520" which will give .170" before coil bind, and has gone as high as 7500 rpm, and he notes none of the issues previously mentioned such as broken parts from spring surge or valve float, probally because he has no spring surge or valve float, who would of figured. My opinion was based on my experience with my own builds which are naturally aspirated, and here is someones experience with forced induction.

Type 4 Unleashed wrote:I have talked to Chris at Pac Racing about the Beehives I bought from them that are recommended to be ran at .050" before coil bind, because they are designed to be ran close to coil bind.

Type 4 Unleashed wrote: My point being, for example Pluto is no longer considered a planet ? And the New thinking is the Minimum is now the Maximum or is it the Maximum is now the Minimum ?