930 turbo valve springs question
 

Hello, I have a set of valve springs that seems to be aftermarket. They are stiffer than oem ones and got lightened retainers. Could someone help me identify them? Also they are different length, could you tell me which one goes to exhaust and which to intake?

Thanks in advance http://forums.pelicanparts.com/uploa...1640292365.jpg
http://forums.pelicanparts.com/uploa...1640292386.jpg

The "holey" retainers were a signature of CMW a bunch of years ago. Not sure if they still sell those. They probably sold springs too, hard to tell if yours are CMW.

Have the springs measured for stiffness. Good to do for any springs, but if memory serves correctly CMW springs were known to be super stiff, which some builders don't recommend these days.

They are different lengths because one is worn out. And the surface finish suggests the springs were rusty at one time. Time for new ones.

The surfaces should always be parallel, not angled like the one on the left. Any pits or rust will cause a stress riser that will cause the spring to break in service.

The machine work.on the retainers looks quite rough. The "speed holes" didn't even get deburred, let alone chamfered. Looks like I can see chatter marks on the lathe cuts. I would not use those in an engine.

I would put those in the scrap bin for a variety of reasons. Intake and exhaust are the same part number and the factory ones are fine to use with stock and slightly hotter cams.

First I'd ask about the engine stock or modified? what cam, boost, redline and etc?
Then as part of the job spec the old springs with the cam and everything else to see what the previous builder did.

You want a heavier spring with aggressive cams and fast lobe ramp rates, but it comes at a price, the heavier springs actually costs you HP (and extra wear). Heavy springs you almost have to jump straight into the high performance category, because you first have to overcome the loss from the springs before any gains.
Stock springs will work well into the upper mid-performance range.

Thank you for your answers. Springs are going to trash bin.

NASCAR components adapted to Porsche head.
The springs are ridiculously stiff. Throw them away and find a source for either Porsche stock springs (if your cams are low lift/long duration) or something more aggressive (we like Aasco) if your valve float concerns exceed production springs.