DB18 Cylinder Head

[clevitt]

My DB18 cylinder head is being skimmed following a head gasket failure. The machine shop reported that after machining, it was revealed that the waterways had been welded over, so only the block is water cooled. They are asking if they should attempt to drill through the welds or tidy up the welds to leave a smooth surface rather the residual pinpricks. Could I solicit expert advice please? Many thanks, Chris

[terryfrombury]

Well, I`m not sure about "expert" advice, Chris, but if there is no water-cooling to the head, I`m not surprised that the head gasket packed up!
I think the key question has got to be why the waterways were welded up in the first place! Unless anyone can suggest anything else, my only guess would be that the head was cracked somewhere - maybe around one of the combustion chambers - and the welding was done to stop water loss.
If that were the case, then re-opening the waterways would present you with another problem. Depends how expensive your machine shop is. Might be worth opening them up again and then getting the head pressure tested. I certainly wouldn`t open them up and refit the head without that.
Best of luck
Terry from Bury

[Crossley Stephenson]

A few years ago I had a similar problem with my Special Sports. The people who repaired the head welded up around the corroded waterways but then put the head back on without opening up the waterways again, result head gasket failure after 500km (surpring it went that long) because there was virtually no cooling to the head. Second time around they opened up the waterways and everything has been fine since.

Michael

[Stan Thomas]

Clearly you cannot use he head again in that codition - but we have a saying in Brmingham - "You can't scrap scrap".

So.

Given the water passages are welded up anyway - why not fill the head with boiling water first to see if there are any leaks, and if not, put the gasket on the head face, mark off where the water passages should be, then drill through where each apperture should be with a series of small holes and cut through and clean up.

Bit of a balls aching job, but at least it ain't gonna cost you anything, and its going to rain this week-end anyway.

Hope it works!

Stan.

[clevitt]

I've decided to ask the machine shop to try and open up the passages, so they may appreciate information about how the passages run through the head. Should they drill at right angles to the face of the head? My assumption is there is a larger waterway that runs the length of the head and then connects to the thermostat housing ?
Many thanks all,
Chris

[Marcel Renshaw]

A couple of photos which might help.It's not quite straight forwards in regards to the machining. My thought would be to mill a slot about an 1/8" deep and drill the holes at either end. That way you shouldn't break into the spark plug holes.

[clevitt]

Using a cylinder head kindly loaned by Marcel Renshaw as a template, the machine shop have managed to re-drill the passageways. They had to do a small amount of TIG welding, so need to do a final skim. Having already skimmed 16thou to correct the warp caused by the overheating , they have concerns that additional skimming could leave the valve head dangerously close the top of the block when fully open, and have asked if there is any data on the amount of valve lift. I can't find any data in the usual sources- David Beale's DB18 Workshop Manual or Trader Service Data 179 : so would appreciate any advice.
Many thanks ,
Chris

[Marcel Renshaw]

If in any doubt I'd have a Copper head gasket water jet cut from 2.5 or 3mm sheet. It would need tempering before use but should give you peace of mind.
I'm glad the head was of use.

[terryfrombury]

Can you laser-cut copper? I don`t know where you`re based Chris, but a friend of mine near Northwich has a laser-cutter, so if you had a pattern, and you can laser-cut copper, then he`d be delighted to help.
Terry
PS Have you pressure-tested the head to check there isn`t a crack?

[Petelang]

Apparently you can't cut copper with laser. It has to be water cut. I recently has some work done in Stainless steel they cut that by laser but when I asked them to cut a copper head Gasket they told me it was a no no.
Peter