valve lift/coil bind
 

Just wanted to confirm if I am doing this correctly?

Engine 3.4 turbo.

intake valve cam lift according to the grinder spec is .485" (12.3mm)
If I compress the stock inner spring together with the retainers, coil bind occours at approx 20.5 mm, measured where factory states to measure.

So if I set the installed height at 34.5mm subtract the valve lift of 12.3 and subtract 1.8mm for valve clearance that would leave me at 20.4

Am I safe? Is the stated cam lift of .485 the accurate number to use or am i suppose to calculate it with rocker arm ratio or something to get the correct valve lift?

thanks in advance.

A few thoughts/questions:
You definitely want to measure valve lift and not cam lift for what you are doing, since the spring only cares about valve lift. .485" is almost certainly the valve lift, but do confirm that.
What is the valve clearance that you are allowing for in your calculation? Is that representing minimum clearance from coil bind?
When I put a high lift cam on stock springs years ago, I was told to stay at least 1 mm away from coil bind. I was able to do that with a cam that had .490" lift on the intake valve. This was on 2.7 heads. Every setup is a little different of course so you are right to measure each head/spring to confirm.

Ah ok, so the specs the grinders publish is the actual valve lift...485 in my case.? i did not know if i had to calculate that # with something else.

based on my research I should aim for 1.8mm (.070") valve clearance.
So if i did 34.5mm installed height minus 12.3mm(.485") that would give me 22.2mm.. which leaves me with 1.7mm clearance from coil bind at 20.5mm. So seems to be a perfect fit if the numbers I am using are correct.

From what you describe, it sounds like you should be OK then. Probably best to verify lift at the valve to be safe.

Since you are using a high lift cam, it would be a good idea to check all your springs to make sure they are good. Since I am a DIY, I got a valve spring checker from Summit Racing that measures spring pressure using a bench vise as a clamp. You can check them at 34.5 mm height to make sure they give similar lbs on the spring checker.

Ok so I must be doing something wrong. Today i received new stock springs and checked the coil bind on them and found that it was about 21.5mm instead of 20.5 on my old ones.. which only leaves me with .7mm clearance before coil bind instead of the recommended 1.8mm... So then started to think ..

I noticed a stock 964 cam has a published valve lift of .470" 11.9mm.. So even if i used stock 964 cams , stock valve springs, stock installed height.. 34.5 minus 11.9 =22.6 with only 1.1mm clearance before coil bind.. less than the recommended .070"?

Something must be wrong?

Am i missing anything?