Valve head cleaning and guide wear..

[glynherron]

Hi guys

I've stripped down the head on my s4s and need some advice on the valve guide wear.

The manual doesn't state what wear is acceptable so I don't really have a datum to check against.

What should I be looking for?

At what point should the guides be replaced?

How should I clean the carbon from the back of the heads and stem?

As always, thanks for your help

Glyn

[top-plumber]

Smoking when running is normally a sign of worn valve guides.

When cleaning valves I protect the stem with some tape and place in a drill chuck. Spin up and then use various grades of emery cloth to polish the valve.

That's my approach any way.

[sailorbob]

Valve stem clearance in guide:

 

Inlet - 0.015 - 0.053 mm (0.0006 - 0.0021 in)

Exhaust - 0.030 - 0.070 mm (0.001 2 - 0.0027 in

 

Worn guides do not need to be replaced, they can be k-lined.

[jonwat]

With the valve closed, lift it a half inch or so & rock it from side to side, anything more than very slight movement is too much & indicates wear.

To clean the valve, mount an electric drill in the vice & place the valve in the chuck so you can use an old chisel or grind an edge onto an old file to get the worse of the coke off the valve. You can then progress to emery cloth :-)

[DaveyT]

Egr valve cleaner works pretty well too, for removing carbon deposits, though I've no tried it on valve stems.

ID your valves first? and soak overnight in a closed container.

Should make getting the worst off much easier

Dave

[glynherron]

Valve stem clearance in guide:

Inlet - 0.015 - 0.053 mm (0.0006 - 0.0021 in)

Exhaust - 0.030 - 0.070 mm (0.001 2 - 0.0027 in

Worn guides do not need to be replaced, they can be k-lined.

Thanks for the specs. How would this be measured?

Smoking when running is normally a sign of worn valve guides.

When cleaning valves I protect the stem with some tape and place in a drill chuck. Spin up and then use various grades of emery cloth to polish the valve.

That's my approach any way.

Thanks. I used this method on my old mini many years ago. I just wondered if there was a modern way!

Cheers

With the valve closed, lift it a half inch or so & rock it from side to side, anything more than very slight movement is too much & indicates wear.

To clean the valve, mount an electric drill in the vice & place the valve in the chuck so you can use an old chisel or grind an edge onto an old file to get the worse of the coke off the valve. You can then progress to emery cloth :-)

It's strange, some of the valves have no play whilst others seem to have much more. The exhausts in the brass guides are by far the worst. Engine has only done 55000 miles. Is this considered normal wear?

I wish that there was a definitive "open valve 10 mm. Measure lateral play. In excess of 2mm replace guide"

Egr valve cleaner works pretty well too, for removing carbon deposits, though I've no tried it on valve stems.

ID your valves first? and soak overnight in a closed container.

Should make getting the worst off much easier

Dave

I thought about soaking them in oven cleaner. Get the Mr Muscle out!

Is egr cleaner the same as clutch and brake cleaner?

[Simon350S]

That 'oven pride, stuff would probably work a treat, but how it would effect the valve itself I've no idea. It's really toxic stuff!!!

[sailorbob]

Thanks for the specs. How would this be measured?

A micrometer is used to measure the valve stem and a bore gauge is used to measure the guide's bore. The latter can be tricky to accurately measure, especially with the ovalling that occurs from the wear.

[bullit]

what a long story....

 

first, the most hobbyist do not have the equipment to measure  the guides, (only measure with two point bore gauge, and not with 3-point)

 

second , I suppose there is no hobbyist that can place k-line guides, you need special

equipment and a hand full off  k-line guides......(besides  i think +/- 7.13 mm is not common k-line size)

 

be handsome,  take the head to a engine overhaul centre, they have the experience, and the stuff

to  repair the head in no-time, while you have a lot work to lap or grind the valves and still it is not perfect

 

  

sietse  // holland

Edited October 21, 2014 by bullit

[top-plumber]

Yes there is the throw money at it option I suppose. :-)

[DaveyT]

But if it ain't broke.....why is the head off anyhow?

[bullit]

 

[top-plumber]

I may have sounded a little abrupt with my comment about throwing money at a problem. This was not my intention. As a time served engineer and tool maker my confidence is very high when tackling issues with my car. I sometimes do not take into account others may not have the same confidence or access to a machine shop that I enjoy. A second opinion is always a good option in these circumstance.

Regards

Wayne

[glynherron]

It's off as the engine is out and having a bottom end rebuild. To me it made sense to check the head.

I no longer have access to machine tools but I'm confident in my own ability.

I don't subscribe to the "if it ain't broke don't fix it" as when these motors do break they cost a fortune to repair.

Thinking of replacing the cam followers whilst everything is apart.....

[sailorbob]

You shouldn't need to replace the cam followers unless you have excessive bore wear as you should already have the steel followers (21 mm skirt length). If the bores are worn then you'll need custom oversize followers made.

[glynherron]

You shouldn't need to replace the cam followers unless you have excessive bore wear as you should already have the steel followers (21 mm skirt length). If the bores are worn then you'll need custom oversize followers made.

That's good to hear. When did the spec change from cast?

[sailorbob]

I'm not entirely sure when they were introduced. In the engine service notes section EB there's an update dated Feb 1991 that refers to their introduction on the 910 engines.

[glynherron]

Thanks. That's one thing less to worry about

[top-plumber]

Yeh that's good information. Didn't realise that the upgrade had been done. Must read the service notes again soon.

[glynherron]

Took the head to an engineer. All guides need replacing.

So how much is reasonable?

New valve guide inserts (American parts)

Cut seats and re face valves

De coke

Machine exhaust port face

Clean

Pressure test

[Vulcan Grey]

That service was about $370 in american.

 

I would make sure they use the correct valve guides!  The intake guides are cast iron, and the exhaust are silicon-bronze.

Valve seats are sintered steel.

[jonwat]

Took the head to an engineer. All guides need replacing.

 

That's like asking your barber if he thinks you need a haircut. 

[glynherron]

That's like asking your barber if he thinks you need a haircut.

I see your point but as all the valves wobble and some dramatically I have to put my faith in someone.

I've used him to grind my flywheel and polish the crank previously.

[glynherron]

That service was about $370 in american.

I would make sure they use the correct valve guides! The intake guides are cast iron, and the exhaust are silicon-bronze.

Valve seats are sintered steel.

Hi Travis. Thanks for your feedback.

He doesn't like to press out the old guides in case they pick up on the way out. He also doesn't like to heat heads up and prefers to bore them out and collapse them in.

He fits Rapid Technologies repair sleeves which he has used for many years.

Bad idea?

Should I go somewhere else

He specialises in vintage and classic engine repair

Thanks

Glyn

[sailorbob]

There's nothing wrong with boring out and collapsing the thin wall that's left out but you would only do this if replacing the whole guide. The Rapid Technologies repair sleeves are similar to the K-Line or Nucleus sleeving systems.