Cylinder Head Valve Timing

[Val]

Hi All

I am in the process of re-building my cylinder head and wish to set the valve timing accurately using offset keys when I reinstall the head. I have done this before on other makes of engines so have the dial gague etc.

My cam is an '08' and the only figures that I can find are Inlet valve No1 opens at 11deg BTDC and closes at 47deg ABDC?  "Values with Reference to 0.4mm Valve Lift".

Am I right that this means 0.4mm of valve lift at 11deg?

Is there a deg figure for full valve lift? Is it eque distant (ie half way between these two figures) as I am more familiar with using the full lift figure and would have thought that it would be more accurate allowing for wear of the cam lobes.

Any advice from the experts gratefully received

Val

[Val]

Bump.

Anybody?

[DavidBrough]

Hi Val,

My manual refers to the UK 280SL/8 having the 09 or 02 cams giving 0.4mm of lift at 12deg BTDC on number one inlet with the 08 cams at 11deg being fitted to the S, SE, SEL saloons and US only 280 SL/8's for what its worth. However it also says that the measurement is to be taken at 0.4mm of valve lift to eliminate any errors due to valve clearance. I've never done this job myself so can't really comment further but hope that helps

[Val]

Hi David,

You are right. I should not have an 08 cam, but my engine was changed by Roger Edwards Motors for a re-built unit about 10 years ago. The 're-build' seems to have consisted of a re-bore and very little else. Certainly the cylinderhead, which the invoice says had new guides and seats, had only very badly fitted exhaust guides (stuck in with silicone!), So I am in the process of fixing this. The cam is with Kent Cams for a clean up and possible grind, so they may be able to help with timing figures, but I would still like to work out where full lift should be.

Val

[tel76]

Hello Val,
I would be interested to know what Kent cams are going to do to your camshaft,if they regrind it will give all sorts of problems with the valve geometry.
Ask the Benz Dr.
I have a cam that is past its best so that is why i am interested.

[Val]

Me too!  I'm getting assistance with the head from a friend who is an engine builder at Jim Stokes Workshops, Kent do all their camshaft work and are aware that follower geometery is important on this engine. I understand that they normally use some form of metal spray to build up the lobes before regrinding them. I'm waiting for them to let me know what it needs.

[Val]

Well I just got my cam back from Kent Cams (http://www.kentcams.com/).

They have made a beautiful job of it. Not only have they built the metal back up (by using a process called 'metal spray'), but they have also reprofiled the camshaft to 02 specs They have also cleaned up the bearing surfaces and the camshaft keyway like new.

Total cost, including cam lube, return postage and tax £148.00

Hope this is of future help to someone.

[ja17]

Hello Val,

We have tried to rebuild cams also. However the originals were surfaced hardened (nitrited).  The repaired cams were not surface hardened and did not last. Hopefully you will have beter luck.

Some of you may have noticed the "chrome like" surfaces of the cam and rockers. Any deep wear spots on these surfaces are darker metal. This occures when a spot on the hardened surface is worn through to the softer base metal.

[Val]

Kent are probably the No1 camshaft manufacturer in europe. They make cams for several Formula 1 teams as well as much of the classic car industry. They make new camshafts for Jim Stokes for the Alfa Romeo 8c 

A correctly reground cam should be case hardened. Correct fitment, with all new followers, use of a quality cam lube, and running in at initial startup are vital to long life. I've built many engines over the years and have never come across a cam that was not case hardened, but they ALL need running in to work harden the surfaces as well.

This is a short article that explains why : http://www.pumaracing.co.uk/cam1.htm

I'll make sure to let you know how I get on once it is fitted and running

[tel76]

Hello Val,
I sent an email to Kent Cams requesting information of there process and i got the following reply---  We have no experience of these camshafts and do not offer a metal spray/power welding service.  It was signed by Del Johnson.
You did indicate that you were going through a third party,did he send it to someone else,i would be interested to know who did it as i require mine doing also

[Val]

Hi Eric

That is most strange! It was definately Kent Cams that did the work and they offered me a choice of profiles. I will talk to my friend to see if he has some special access to a secret department there 

Very perplexing!

I'll try and come back to you with a name and direct contact info. Could be a few days though as I am not seeing him until the weekend.

[Benz Dr.]

I've seen spray welding done and I seem to remember they guy heating the base metal with a torch until it was red hot. This was a round part which was in a large lathe so I imagine this is done mostly on round shafts or anything that can be turned in a lathe.
Once the metal was hot he opened a valve and a powdered metal was sprayed on to the heated area. This powder melted imeadiately and became part of the shaft. I assume this is better than regular welding which would be harder than the surounding area which could lead to cracking or stress fractures. In this case he ground the area to a V and filled it back in. In the case of a cam shaft I suppose they would build up a layer that can be ground down to the correct specs.
If you remove a small amount from the base circle it will move the cam lobe further away from centre if done properly. This would be an offset grind.

If you have problems with rocker geometry the best cure is to use cam bearing shims which will raise the cam shaft allowing for more adjustment at the ball stud. I like to be able to see the necked down area between the thread and the hex - anything less than this is asking for trouble. This is so critical that you can ruin a set of new valve guides in less than a half hour of running at idle. There is no cure for this and the head will have to come off but the valve guides can be sleeved if they're new ( in other words, minimal wear ). You would need to check the seats for valve placement but it shouldn't be a lot of movement with that little running.

The .4mm is how much the valve should be lifted before checking valve timing. It really doesn't mater how much you use as long as all the valve lash is taken up. You need a degree wheel placed on the cam shaft and a dial gage placed on the valve spring retainer. Most cam shafts are out 3 - 6 degrees after machining is done on the block and head but you can advance the cam slightly past spec - maybe 1 -2 degrees but no more than that.

It's kind of tricky unti you figure out how to hold the dial gage and sort out a pointer for the degree wheel. I think you have to doubble the figures for cam timing as read from the degree wheel.

[tel76]

Hello Dan,
Can you clarify your observations-----  I like to be able to see the necked down area between thread and hex:
Hello Joe,
Can you give us more info: on your bad experiences with camshaft metal prying and re-profiling

[Benz Dr.]

If you take a ball stud apart you will see that it has threads at the bottom, a small gap, and  threads at the top. The bottom and top threads are machined slightly out of sync to each other which makes the top thread bind enough to keep it from turning on its own in the ball stud fixture.

At the top of the thread there will be another gap or space and then the hex where you would use your wrench to turn it. Above that is the ball that the rocker sits on.
Between the hex and the top thread there's the space that I'm referring to and that's what I like to be able to see. Maybe even a bit of thread showing - the more there is the better the rocker geomerty will be.
If you have the ball stud screwed all the way down so that the the hex is pretty much hitting the top of the ball stud holder the rocker will be far too low on that end. The valve will be pushed sideways instead of straight down every time ther the valve opens. The exhaust valve seems to be a bit worse for this because the shaft is larger and it won't bend at all. Actually, neither of them bend and both intake and exhaust are affected equally.
This may not affect old worn out guides as much but it will ruin new ones in very short order. You don't even need to drive the car - it will happen at idle in a half hour or less. The engine will smoke lighly and it will never stop. Every time you pull away from a traffic light there will be a small cloud of smoke. The longer you wait the bigger the cloud will be.

[Naj ✝︎]

Hi, Doc,

Is there any life left in a ball stud like the one in the picture?

naj

[al_lieffring]

A poor boy fix is to take a disc grinder and remove the nub from the top. This is a lot easier to do on the bench with the cylinder head off of the car. The new ball studs I installed with my engine rebuild I bought 25 years earlier, I have no idea what they cost now. But by grinding off the nub it will reduce some of the valve train noise and last a couple of years.

[Naj ✝︎]

Thanks, Al and Joe.

naj

[ja17]

Hello Naj,

Ditto with Al, much better to grind these off then leaving them with those wear crowns. You can remove the ball stud  and grind the crown off flat, on a bench grinder also. Do not try to grind it round. A flat grind is easiest and how them come when new.

New is best, however once you begin replacing worn parts it is hard to find a place to stop. You would have to decide whether to replace the worn rocker arms (socket for the ball stud) wears also) and then you would have new rocker arms on a used cam?   $$$$

[tel76]

Hello Val,
Any news on who did your camshaft repair.

[Benz Dr.]

I use my valve grinder to nip off those protrusions. Thing is, they're completly worn out when they look like that so it's a temporary fix at best.
Ball studs are being reproduced. They're not that much but start to add up because you need 12 of them. Figure on 400 - 500 dollars for a set.

[Val]

Eric

Really not sure why you got the response you did, perhaps you would be better ringing them. It is definately Kent Cams, and the returned cam has been stamped with the code 'KCV1087' and the box is marked 'Mercedes to V1087' So at a wild guess, the 'KC' stamped on the cam could be the initials of the person who did the grind?

Hope that helps.

Val

[tel76]

Hello Val,
I have just spoken to Del Johnson of Kent Cams and he confirms that KCV 1087 is one of there profiles but as they have no facilities to metal spray all they did in your case was to regrind the camshaft,he acknowledged that there will be a tappet adjustment issue when you come to refit it.
I would be interested to know how you resolved this.