Stupid Question???
 

What is the difference between the 41.5mm valve (930-105-419-51-M154) for the 911 and the 41.5mm valve (930-105-419-50-M154) for the 930? Is the shaft different? Different material? Curious to know about the intake valves as well.

I think they run more guide clearance with the turbo engine, (smaller stem) and Sodium filled, Thats my stupid answer and I am sticking to it.

They both use the same valve stem seals, seats, springs and retainers. Also, the valve guides are the same size for both on 1st and 2nd oversize, in fact, the part numbers are the same. So far everything seams the same except the valve part number and price.

PET shows '51 for the 930.20/21/26 and '50 for the 930.66/68 So one's for the Turbo and one's for the NA version.

Yes, I realize the part numbers are different. My question is what is actually different about them physically. All other pieces are the same (valve stem seals, valve guides, seats, springs and retainers). The valve dimensions are the same. So what really makes them different than the N/A valves?

I think if you mic the stems you will find the turbo valve stem to be about .001 smaller than the na valve stem.

Why wouldn't you just ream the guide bigger rather than having a different size stem?

What is the reason for more clearance?

they run hotter and have more thermal expansion? that would be my guess, i guessing we can guess on this topic:)

I'm trying to justify why an (apparently) identical set of intake and exhaust valves that are $268.50 for N/A will cost me $600 for my turbo. I want to believe there is some justifiable reason and not just the turbo tax. I'm curious to know if there is a metallurgical difference between the two.

Just a guess, but I'd bet the turbo's are inconel, nitrided or possibly sodium filled.

Welcome to the world of 930 ownership.. take any n/a price and go x2 to get the 930 cost.... As a buddy of mine once told me.. " you have to pay the TROLL the TOLL to play".
I'm sure there is a slight diff in the parts...

Is there anyone who actually "knows" the difference?

Call Danny at P3automotive.. and ask him. He will know.
P3 Automotive in Centerville

Danny L King
P3 Automotive
445 Miamisburg-Centerville Rd
Centerville, OH 45459
http://www.p3automotive.com
turbotech@p3automotive.com

Thanks Eric.

I am sure I have read that they are sodium filled.