surface grinding valve heads flat
 

I have worn valve stem heads were poor servicing in the past has caused the rocker arms to wear the top of the valve stem heads

This is on a 2006 d5 185 with 200k miles

I did replace the worn rockers sometime back but due to the high cost of the valves left them alone

Having had the rockers out today I have noticed that these rough topped valves are prematurely wearing into the underside of my new rockers

Has anyone ever tried putting the valves onto a magnetic base and taking a thin pass over them with a surface grinder to restore a true flat face once more ?

Concerns I have are changes to the geometry of the rocker angle ?

Are the valve heads surface hardened only ?

Clearly the best course is new valves but at £25 each times 20 that's about what the car is worth

Just wondered if anyone has done this in the past with success

Have no experience in this but I'd consider-

1) Currently valves are wearing the rockers - how many miles will elapse before the valves ruin the rockers? (again)

2) You have concerns about removing/loosing the hardness in the valve head by grinding. If you do grind them what if anything is the down side - you'd have 2 surfaces of more equal hardness perhaps and more equal wear.
Is this situation better or worse than position 1?

3) At 200K how many more miles do you expect/want/need from this car? which option above is more likely to get to this point.


If you do decide to grind the valves I'd try to keep the valves as cool as possible - spray water from 2nd pair of hands??
When the valve tops are flat again can't see how geometry of the rocker angle can be altered - perhaps I'm missing something there.

I suspect there are many other options/considerations. - Just my 2d cos no one has offered any comment....yet
What ever you decide good luck.

Cheers
Bob

Have a look at the prices of inlet and exhaust valves on www.autodoc.co.uk

They’re a lot less than £25 each.

Hi but do autodoc have stock ?
as I ordered some koni sports front struts inserts from them 2 weeks ago as there site said they are in stock, after 2 days I asked on there on line chat when they will be sent, and they told me it was being sent soon, I asked another 2 days after and they told me the same,
then after another 2 days they sent my a email saying that they did not have stock and will not be getting any stock, and if I give them my vin they could find a part to fit my car, but I ordered the konis, it took another 5 days to get a refund,,
also there site makes it look like they are in the UK, they are not, they are in Germany ,
in the end I ordered them on ebay yes it came to £15 more for the pair but I had them delivered with in 4 days, they also came from Germany,
sorry about the long email that has nothing to do with the valves, but I don't want you wasting time ordering from them only to find out they do not have the valves,
also they still have the konis listed on the site,
Dave

They have a .co.uk web address and a bunch of others, it’s all the same company offering to deliver to the UK. I don’t particularly care where they ship from. My irritation with them is that they don’t offer an express service, and on one occasion their site showed something in stock that wasn’t.

However, I’m now an enthusiastic customer having ordered a bunch of stuff for my Mazda, Mini and Volvo. What I like is that they offer a broader range of replacements eg I can choose between Sachs struts for my Mazda 5 at c £40 vs a no-name brand from them at £25 or go to ECP and use their discount to get the Sachs struts from ECP at £70 or no name Brand for £40. Same with ATE, Lemforder, SKF etc.

They have a live chat function as well where you can check availability. It’s not completely foolproof, I suspect they don’t hold everything in stock and rely on their suppliers having accurate stock records.

Anyhow, back to the original post. Yes, you should ideally have replaced the valves as well as the rockers. You don’t need to pay £25 each for new valves and I wouldn’t waste time trying to regrind the top surface.

As eternal optimist says above, don't waste your time trying to grind the tips of the valve stems - they are usually only case hardened, in all probability nitrided, depending upon the original spec and are not designed to be re-flatted.