Poor quality valves Topic is solved

[Sveedy]

Well it kind of seems like having different weight valves would change the effective spring rate, but again, I'm no expert.
I'm going to grab a small scale today and do a little valve weighing.

[Sveedy]

Even though it doesn't make much sense, the new Skandix valve weighs apx. 2.8g more than the stock valves, even with the choke down on the stem.

Results for those following along :

Cyl #1
Valve A - 40.7g
B - 40.5g
Cyl #2
A - burnt
B - 41g
Cyl #3
A - 41g
B - 40.8g
Cyl #4
A - 40.9g
B - 41g
Cyl #5
A - 40.7g
B - 40.8g

New Skandix - 43.6g

[Sveedy]

Could the difference in weight between the old and new be due to different amounts of sodium in the stems ?

[volvolugnut]

Could the difference in weight between the old and new be due to different amounts of sodium in the stems ?

That was one of my thoughts. Also, the necked area might be a joint were the valve was rejoined after filling with sodium.
volvolugnut

[abscate]

I’m not sure these new valves are sodium filled.

Spring frequency is SQRT (k/m) where m is valve plus spring mass , so the frequency of oscillation won’t change much. I don’t think an extra 2g mass will amount to much extra force on the spring , has anyone measured k on valve springs?

I am going to swag it at 1000 N/cm or so

[Sveedy]

So I ordered two valves from ProParts Sweden. They have the proper dish and stems, but weigh 4g more than stock.
Based on weight, I'm better off with the Skandix, even with the stepped stem. Kind of surprised that the manufactures miss the stock weight by so much. If your copying something, then in this case, I'd think size and weight would be both be considered.
However they are consistent within manufacture from what I've seen.

[volvolugnut]

I’m not sure these new valves are sodium filled.

Spring frequency is SQRT (k/m) where m is valve plus spring mass , so the frequency of oscillation won’t change much. I don’t think an extra 2g mass will amount to much extra force on the spring , has anyone measured k on valve springs?

I am going to swag it at 1000 N/cm or so

If we had the k value for the strings, cam lift and duration specs, and I had the will to dig into all the dynamics calculations, an answer could be found if 2 or 4 grams added spring mass will make a difference. Most likely it would only float the valves at max RPM if too much valve mass.
Calculation not likely to happen for all above reasons.
volvolugnut

[abscate]

Someone who has a spring off needs to measure its length, put 4 liters of water on it , measure compressed length , and report both numbers

An Apple experiences a gravitational force of 1 Newton, at the core of the issue

So let’s do the math.

The valves open about 1cm = 0.01 meter

To compress the spring 1cm thus takes mag (F)= k mag(x) = 1000 N/m * 1E-2m = 10N

The 40g valve has to be accelerated from rest to open at 200 times a second (50E-3 seconds) roughly so

F = mA= .040kg * 1e-2m/50E-3)^2 = 4E-2 * 1E-2/25E-6)=4E-4/25E-6 =1/6 E2= 16 Newtons

That’s not a huge force for forged steel working parts of the engine amd valve train

[abscate]

Skandix now showing that valves and valve stem seal kit will be back in stock end of September.

[Sveedy]

Well what my research has shown so far, is that I'd probably be fine with different weight valves if it was a NA engine.
And if I didn't run it at high rpm's.
And if it didn't have all of the performance upgrades that it has.
And if I wore a tweed sport jacket when I drove it.
And if that jacket had leather elbow patches.
And if I smoked a pipe (but I do )

Well then apparently I'd be just fine.

So I'm in a holding pattern right now. It's either replace all of the exhaust valves with aftermarket valves, which will all be the same, or try for used stock ones. Mr. Spinner ( Robert DIY ) is now looking into getting a couple of stock ones for me, so fingers crossed. If anyone can come up with them, he can.