Valve seat question

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Valve seat question

Postby underscore » Wed Aug 05, 2015 10:21 pm

Per the CS press release:

viewtopic.php?t=32149

To improve heat dissipation in the valve area next to the valve seat, the 3S-GTE cylinder head uses the world's first laser-clad seats. Welded by laser beam, the one-piece structure allows heat to dissipate more evenly.


Now my motor is currently apart and the machine shop is recommending new valves, however I know that changing the valves requires machining the seats. This is a problem for me since I want to keep everything that was RC specific, so I need to know if machining the valve seats is going to change anything that was only done for the RC/CS/GrpA. The release isn't terribly clear though, so I can't tell if the laser-clad seats are in all 3SGTE's or just the CS/RC.

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Re: Valve seat question

Postby corax » Wed Aug 05, 2015 10:28 pm

I have no answer for you, but the way it reads, it sounds as if the seats are welded to the head which would give slightly better heat transfer than a press fit . . . but, even with a laser, how does one weld a hardened steel valve seat to an aluminum head?
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Re: Valve seat question

Postby underscore » Wed Aug 05, 2015 10:36 pm

What throws me off is that the parts diagrams show valve seats separate from the head, with their own part numbers. If they were laser welded to the head there would be no way to replace them, in which case there would be no reason to list them on their own.
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Re: Valve seat question

Postby ___Scott___ » Wed Aug 05, 2015 10:50 pm

I'm just going to speculate here since I don't have any specific knowledge on the issue.

If the valves need to be replaced it's probably because the stems are worn out of spec. If the stems are worn to that extent, I would also expect the seats to be heavily worn too. Since laser cladding only deposits a thin layer of whatever it is they are welding to the base material, I would expect that it's long gone anyway. So grinding the seats to prep them for new valves doesn't seem like a terrible thing, especially if you are not planning to enter any WRC events.
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Re: Valve seat question

Postby underscore » Thu Aug 06, 2015 9:18 pm

I managed to find a bit more info from when Toyota used it on the 1ZZ:

The laser-clad valve seat is a layer of highly wear-resistant alloy directly formed in the cylinder head body by using a laser. The laser-clad valve seat eliminates the need for a space in the cylinder head into which separate seat rings are shrink-fit


http://www.spyderchat.com/1zzfe.pdf pg 5 [7]

So it sounds like the laser forms the material for the seat in the head, so machining it won't change anything. Though I'm still confused how Toyota has part numbers for press-in seats if they're supposedly laser clad.
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