8 or 9mm valve stem.

Onlyvw · Post by **Onlyvw** » Tue Nov 15, 2011 12:58 pm

I am building a quite serious wbx 2223 (96.5x76) turbo engine and will change the valve sizes. Original wbx has 9mm valve stem on exhaust (probably because of the sodium) I will now order a custom set from Si valves. What is recomended 8 or 9mm valve stem on exhaust??? Is it also recommended to cut the guide in the exhaust port???

buildabiggerboxer · Post by **buildabiggerboxer** » Thu Nov 17, 2011 10:52 am

Change to 8mm stems as you're changing valves any way. many drag cars now run 6 or 7 mm stems, but they must have a short life, and yes, you can remove the guide boss OK, but i would just streamline and flow it, personally i use a big beefy exhaust guide with turbo use, rather than a streamline and thinned race type guide, Ive had these crack and bits break off at the thin end.

Onlyvw · Post by **Onlyvw** » Thu Nov 17, 2011 1:13 pm

Thanks for answer I then will change to 8 mm stem.
Would you have cut the valve guide or just let it be for street use??? Engine will run on E85.

tencentlife · Post by **tencentlife** » Sat Nov 19, 2011 7:55 am

Wbx did not use sodium-filled valves, they're just a welded valve with a 9mm stem.

If I was boosting I would stay with that size. A narrower stem would offer a flow increase that would be more significant in a NA setup, but with the more extreme heat of a boosted app I would favor the stronger valve myself for longevity, and the larger stem offers more heat-transfer area with the guide; that's even more significant if you are trimming the guides. The 8mm will work just fine I'm sure, I think your choice comes down to how long you want to go between valve jobs.

fastback · Post by **fastback** » Sat Nov 19, 2011 8:44 am

tencentlife wrote:Wbx did not use sodium-filled valves, they're just a welded valve with a 9mm stem.

how shure are about this?

tencentlife · Post by **tencentlife** » Sat Nov 19, 2011 9:51 am

100%.

There was good reason to use a Na exhaust valve in the aircooled heads, but no reason to in a watercooled head. Manufacturers don't generally waste money on such expensive parts when there is no need.

But don't believe me. Take an OEM wbx exhaust valve and saw thru the stem. Solid steel all the way thru.

fastback · Post by **fastback** » Mon Dec 12, 2011 12:36 pm

and so i did

seem to be stainless at the seat end. as it is non magnetic up to the weld splice

tencentlife · Post by **tencentlife** » Mon Dec 12, 2011 4:17 pm

I've posted the link to this article a few times, it's a good explanation of valve metallurgy:

http://www.enginebuildermag.com/Article ... lloys.aspx

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8 or 9mm valve stem.

8 or 9mm valve stem.

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