Need spring rate height for 993ss cam

[Ed scuba]

I need spring rate height for 993ss cam. I'm having my cams regrind to 993 ss by John Doughtery. He is EXTREMLY hard to get ahold of and my machinist needs this info NOW If you are reading this John I need this info and I need to get my cams and rockers back NOW.
This is for my 3.2 l 1984 Carrera. Please anybody know this info?

[Walt Fricke]

Ed

What is spring rate height?

Springs are set by installed height, which sets the seat pressure.

The spring rate depends on the springs themselves.

You shouldn't need to know your camshaft's specifications to know these parameters.

You, as the engine designer, need to determine the seat pressure you need. Then you can use the spring rate to determine how much preload you need on the springs, and that will give you the installed height, which you set by adjusting the number of shims under the springs and the spring cup. My race springs have always needed machined spring cups, with the inner spring seat machined down to match the outer.

But I've never worked directly with a spring company. Instead, the machinist/shop which sourced the springs and titanium retainers has given me an installed height, which I then used to assemble the valves into the heads.

Never had anything to do with the cam grind as such. I suppose that the hotter the grind the more seat pressure you might need over stock to keep things under control.

I sure hope John is OK. He ground cams for me last summer in reasonable time, and got some rockers back to me this fall. Quickly answered an e-mail I sent him on a related question late October.

[Ed scuba]

You are right. I looking for installed height. If I'm reading this right then I need to know what the spring rate is on the springs that I recieved from EBS as part of the rebuild kit. This is standard kit for 3.2. and that will give me my needed installed height?
Thanks

[Walt Fricke]

Right - just call EBS. You might want to have the lift specs for your cam handy, in case they don't know the characteristics of that cam. But from posts they have made about valve springs, this is the kind of thing they are on top of. I'm quite certain they can give you an installed height.

They may ask you how high you plan to rev the motor, so you ought to tell them that also. The higher the revs, the higher the seat pressure and thus the shorter the installed height.

[series9]

As far as I'm informed by John, the DRC 993SS cam is designed around a 6500rpm redline. Stock valve springs will suffice.

[Walt Fricke]

34.5-0.3mm (in other words, 34.5 is the max height, but you can be a little shorter) is the (Bentley) stock valve spring height for 3.2 heads.

Stock springs are good for a whole lot more than 6,500 rpm.

But I'd check with EBS, because their springs might be different dimensionally than the stock springs, and that could affect getting the height just right - not too short, because that would be more seat pressure then needed, but not too long, for the opposite concern.

Unless he just bought stock Porsche springs from EBS, in which case end of inquiry.

[Ed scuba]

Reply from John, Is that Angels I'm hearing LOL

New cams have .490" intake and .455" exhaust valve lift. Make sure there is a minimum of 1mm between the seal and valve spring retainer at full valve lift.


--http://www.drcamshafts.com