12G940 Sinking the valves

Post by **Declan_Burns** » Thu Jul 30, 2009 8:40 pm

My mate Günther who restores motorbikes and is heavy into car rallying, sunk the valves on my 12G940 last week. This very expensive piece of kit used is made by a company called "Hunger" based in Munich. I never heard of them before. I was very impressed and just thought I'd post a few photos for general interest.
http://www.ludwig-hunger.de/_english/_p ... 84190_6259[/img]<br><br>

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Post by **8009STEVE** » Fri Jul 31, 2009 10:17 am

Nice bit of kit.

Post by **bmcecosse** » Fri Jul 31, 2009 10:50 am

Crikey - we just used a pillar drill and a 45 degree countersink! The special tip was to put a little piece of emery paper under the cutter which stopped it chattering. Result was lovely grey smooth seats. That does look very fancy !

Post by **Declan_Burns** » Fri Jul 31, 2009 11:47 am

Yes, it very fancy indeed. Günter got it as a golden handshake when he retired from Toyota a few years ago and opened up the bike restoration business. He probably would never have bought it himself at 2000 pounds+. Having said that he does use it a lot. I just found it facinating and thought I'd post up some photos.

Post by **bmcecosse** » Fri Jul 31, 2009 5:07 pm

Hope you smoothed away the resulting ridge around each exhaust seat - with small grind stones ?

Post by **MarkyB** » Fri Jul 31, 2009 5:59 pm

Did he cut 3 angle seats while he was at it?

Post by **Declan_Burns** » Fri Jul 31, 2009 6:13 pm

Yes, we actually discussed the ridges this afternoon and yes it will be done.
Yes three angle seats done.

Post by **rayofleamington** » Fri Jul 31, 2009 8:11 pm

Nice to see it being done properly

Post by **bmcecosse** » Fri Jul 31, 2009 8:17 pm

I see it's a 'big valve' head - what engine is this intended for ??
And remember - if the exhaust valves have been 'sunk' by 40 thou - then you will need to put 40 thou packing (ie a ~ 40 thou/1mm washer!) under the exhaust valve springs to keep the same compression as the inlets.
Exhaust valve seats should just be single cut - for very best heat transfer from valve to head. The 3 angle thing is more for inlet valves - but a very narrow 'pencil line' seat with smooth blending either side is even better!

Post by **Declan_Burns** » Fri Jul 31, 2009 10:03 pm

Roy,
I wasn't aware of the single cut on the exhaust valves. We've already done the three seat cut. Günter suggested going for a 1mm contact area between valve and seat. That's what we've done. It's for the 1098cc engine with the HIF 38 carb, AAA Needle, Mg Metro inlet manifold and K&N copy air filter-already mounted and engine running very very well indeed for the last three months. I'm quite happy with the performance as it is with the original head but I'm keen to see the difference with the 12g940. It's all an interesting learning process. I'll fit a washer as you suggest to balance the compression-thanks for the tip-sounds logical.

Post by **bmcecosse** » Sat Aug 01, 2009 4:40 am

3 angle seats on exhausts are all very well for racing engines which are regularly stripped and valves re-seated. For normal use - a wider seat is better/longer lasting on the exhausts. But your 1mm (40 thou) seat will be fine - don't worry about it! You only need to fit the washers if looking to REV the engine - otherwise the springs will be fine up to 5500 maybe even 6000 before bouncing - and it's better to bounce the exhausts before the inlets anyway!