Valve Spring Identification?
 

Anybody recognize these? The brown ones are original Porsche from my '87 top end rebuild in 2007. The purply ones are unknown. Came from my '79's engine.

The stock valve springs have some clearance between them. You can easily drop the inner spring into the outer spring. However the purple ones are a tight fit and rub on each other. You have to push the inner spring into the outer spring with a noticeable amount of forceSeems like this would generate some additional heat.

I have a set of retainers (ones on the left) that look like they're EBS vMax lightweight Ti ones. I bought these separately and it appears I stumbled across them in a good way. They fit in the purple springs better than the stock steel retainers that were in there. The stockers have a bit more clearance from the ID of the inner spring. The taper of the Ti retainer slips it in there tighter.

Thanks,
Kevin

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Hi Kevin,

I just measured three different springs last month when I was rebuilding my track motor. The stock wire measures .150 inches. The "street plus" springs from John Daugherty measure .156 inches, and the "race" springs from my race shop measure .162 inches. I also have specs for the spring rates and seat pressures for these three cases if you want them.

-Andy

Andy,

Thanks for the wire measurements. I have the racy ones since they that measured out to .161 in. wire diameter and 1.285 in. OD of the outer spring. The setup info for them would be great.

By the way your oil cooler donation looks like it's going to work great. I'll share some pics when i'm done "machining" the connection to the case & the oil filter support.

Thanks,
Kevin

The spring at the top left are Eibach. I believe they have a seated pressure of around 105lbs with an open pressure in the 230lbs range

Thanks for the reply. But I think you're mistaken about the Eibach springs. The brown springs on the left are OEM Porsche valve springs that came off my '87 3.2L engine when I did the top end rebuild in 2007.

The only specs I have for race springs are for the V-max springs from EBS. They show a seat pressure of 80-105lbs, a spring rate of 375 lbs per inch, and a max pressure of 280lbs at full lift. Stock springs are 74, 315, and 227 for the same situations. I'm sorry I don't have the installation heights for them.

-Andy

Thanks for the details on the spring rates. The race spring numbers are comparable to what Eibach makes. See top of page 4 and page 5

http://performance-suspension.eibach.com/uploads/File/upload/evs-applications.pdf

Turns out I believe I have a bent valve spring on #4 exhaust. The lot of springs all are a bit tight in terms of how the inner spring fits into the outer spring. However #4E is a bear to remove and reassemble. So I won't be using them.

I'll get a set of the Eibach springs and post a picture to clarify them compared to the other springs I pictured.

I wouldn't use anything that rubbed together like that in my engine.

Well they've been in there since at least 2005. That's the last time the engine was "rebuilt." I'm not saying that's good. Just saying that's how long they've been in service. I completely agree that rubbing springs is intuitively not a good thing.

Manufacturers use an interference fit bitween inner and out to help dampen harmonics in high rpm applications.

Reduced spring rates can occur when the harmonics are present(if severe enough) leading to loss of valvetrain control at the rpm range in which the harmonic is occuring.

Coil springs do grow in diameter when compressed, and I think the larger diameter one grows by more than the small one so the clearance will increase a little bit when installed and compressed. But I am not sure how much this effect would be.

Interesting. How do they account for the change in friction as the parts wear? Does this actually lengthen spring life because the spring surge is not so pronounced?

Good to know about the harmonics. All the others are a light interference fit like Aaron noted. However this one spring pair is fuched up compared to the others. I had to leverage them apart and you can see noticeable wear of the coating on a few coils. None of the others have this condition. I handled ALL of them while disassembling, noting orientation, cleaning and tagging them in my usual anal retentive way. :D

I do not know the specifics. But as far as parts wear, it's a race engine. When the parts wear you replace. Anytime you can eliminate valve float you will lengthen spring life. Spray bar lube on the spring also increases spring life.

One observation was when a valve spring is in severe float, the spring generates enormous heat. The spring gets cherry red, permanently loosing it's ability to be a spring and and as a result drops valve.

I don't see anything wrong with your decision to scrap it. I would question anything that was out of the ordinary and replace for piece of mind.

I did that on a a few odd ARP rod bolts that did not act the same as the rest of the set.

Thanks for the technical tips Aaron. The kicker is one pair of bad springs is easy to junk. Not as easy to replace just that one pair- only sold in sets to the average Joe.

Turns out my boy cstreit has a set of used EBS springs with cups & Ti retainers included so i'll take advantage of that.