Paulyy

What do you reckon, Can you re use them?

I unbent my valves to take measurements for new ones. And they are in spec as the factory ones. Checked with a dial indicator on the lathe.

Dougs951S

i would think the bend point would be a stress riser despite them being back to factory spec. Just my speculation though.

Black51

+1

I'd say once anything metal has been bent, it's only a matter of time... Especially something like a valve that has to oscillate at very fast.

Dougs951S

besides, its sort of impossible for them to be "perfectly unbent". When metal bends, it undergoes plastic deformation which permanently and irreversibly alters and stretches the material's grain structure. It can never be truly "unbent".


edit: off topic, but paulyy would you happen to have a link to that nifty excel spreadsheet you posted once that compared compressor maps? I liked it and I'd like to save it again, Thanks.

Paulyy

To easy.

https://rennlist.com/forums/944-turb...am-inside.html

Dougs951S

I've thought about this, and I have this to say...The worst you have to loose is a broken valve down the road and then you'll be replacing the valves anyway, and you're out a headgasket and your time. Absolute worst case is you kiss a piston. Or....you could run them forever and they could be fine. You could just toss em back in I suppose, but the engineer in me still says the bent point is a stress riser...just cant say for sure if/when it will become an issue. I'm crazy and a cheap bastard to boot, I'd at least consider throwing em back in and seeing what would happen if nothing more than for ****s and giggles.

Voith

Absolute worst case is that valve falls to one or more peaces and those absolutely destroy piston, head and bore to the point that all of mentioned peaces become paperweights and you need to build new long block for 50x the amount of new set of valves.

This valve cost me ~ $8k on my bmw in 2009. I ve lost cylinder, head and piston pictures, but it looked something like piston on the bottom.

Also bmw valve is a lot smaller and weights lot less than 8V 944 valve.





This one is from two stroke V4 Johnson outboard motor, no valve, but one needle from needle bearing got in the chamber and this is the result..

blade7

If they are one piece valves and you used heat during the straightening process maybe, but they've been bent twice now so I wouldn't for the sake of a few dollars.

Thom

lol... I also suggest reusing the headgasket.

67King

+1. Plus, the point that yielded will be weaker due to said change. These valves are forged, correct? That puts a fine grain structure on the surface to make it harder. When it yields, that structure becomes at best non-uniform, and at worst, much weaker.

But at the end of the day, any part that is machined should never be reused unless it is re-machined. And if it is hardened in any manner, it shouldn't be re-used unless it undergoes proper hardening procedures after it is done.

You may get away with it, but I wouldn't think about taking a chance, the valve may break, and then you are looking at a complete overhaul.

Paulyy

Note: I am NOT Reusing them. I was just seeing what people opinions are on doing it. Hence why i re bent them to get sizes to send off to get new ones made.

lart951

This is bad Oman, I foresee Au losing to Holland today, your fault Pauly

Paulyy

Let's not talk about it!!
i'm watching the game tonight 2am kickoff here.
Odds are so bad, $17 for aus to win!!!

My bets are that Netherlands win each half.

67King

Okay, good, so now I can say what I really wanted to. What are you, STUPID, for wanting to re-use a damaged valve that opens and closes at a rate of over 100 times per second, in an area where it'll see temperatures of probably 2000 degrees!? Risk $10,000 to save $50?

Yeah, re-using them would pretty much be the height of stupidity.

lart951

My predictions for this world cup are; Holland or Germany or Argentina. I prefer the Orange Clockwork though