Cylinder Head Woes...

I'd bought an old DX engine particularly so that I could use the cylinder head on my DS in place of the DX2 head that was fitted.

By mid August 2017, and with the bottom of the engine rebuilt, I turned my attention to the DX cylinder head. The rocker assembly had been removed when the engine and cylinder head were separated. 

One of the long tubes that the spark plugs sits within was missing. on closer inspection it had rusted away at the level it joins the cylinder head. I would have to find a way to fix that......I started removing the spark plugs, the fourth one  - where the 'funnel' was missing - completely disintegrated. All it left leaving a knobbly, rusty stump. I would have to find a way to fix that too.....

Remnants of a Spark Plug.......

Using a valve spring compressor I set about removing the valves. The technique is to start with the valve compressor lever closed and the arm would back. Keeping the compressor closed, locate the ends on the valve and spring. Then wind in the arm until the spring is sufficiently compressed to enable you to reach the collars under the cap. To release the spring, use the lever arm on the compressor - don't wind back the arm. in this way, the degree of compression is 'set' so that to remove the next valve, you only need to operate the lever to compress the spring to the right degree. Well, that's the theory.....Initially I didn't find this easy as my choice of compressor had been the wrong one. A 'Laser' brand 0287 model. 

Although it had adjustable width jaws - useful for maximising the space needed to remove the cap and collars from the valve stem, it barely had the 'reach' around the cylinder head to clamp over the valve head. With some careful placement, it worked at first with, as ever, all the thrust washers, caps and collars associated with each valves going in to labelled pots. However after a couple of valves the adjustable end of the compressor buckled and gave way.

Looking for something else to do, I gave the cylinder head a shake a ton of grit and hard core fell out! I was amazed at how much there was!

I removed the remnants of an exhaust gasket and noticed - for the first time - some significant pitting around one of the (exhaust) ports. Worse was to come: on closer examination of the port I found that I could see the back of the valve seat exposed. The area around the seat was badly corroded. I'd had the engine the best part of a year. Why had I not noticed this before!

Exhaust Port Damage

Valve Seat Eroded and Exposed

I had a sleepless couple of nights. Even if the rotten spark plug stump could be removed, could this be repaired? If so, how and by who? Could I trust the repair to hold out? If I left it alone, and reassembled the engine, would I risk the valve seat collapsing into the cylinder - causing significant damage? This was the last straw. I decided I couldn't take the chance and would need to find another DX cylinder head.....

I rang around. Addie had a head but had already invested significant time and money in it: it was out of my price range. Jamie at DSWorld had a look but drew a blank. Darrin at Citroen Classics thought he had one and would have a look around. After an anxious wait for a call back, he came up trumps! AND it was very reasonably priced. 

On 1 September 2017 I made an early morning dash down and around the M25 to Citroen Classics in Staines. My first visit! I collected the head and a few other bits and pieces and was heading back home before 9am - getting back miraculously by just after 10am. I still don't know how I managed that. So now I had three heads..........

DX2 +2(DX) = ?

While this was going on, I went big and bought myself a Sykes-Pickavant 03950000 valve spring compressor. No messing. This is more of a closed 'C' shape design and, although it has fixed sized adaptors, made easy work of removing the remaining valves on  the  heads.

In mid September 2017 I found a local machine shop and got the DX cylinder head skimmed and vapour blasted. Boy did it look good. Stunning in fact!

Shiny..........

Then I noticed a problem...... There was a tiny, tiny, pin-prick hole eaten away through the water way to the outside of the block. The vapour blasting hadn't caused it, but had revealed it. Perhaps no bad thing. I was however gutted....

The hole was right on a corner at the water pump end, with the erosion perhaps caused by the flow of coolant through the head. I compared the DX head to the later DX2 head and found that the casting had been changed on the DX2 to include a large, prominent extra lump of casting at that corner. Perhaps it was a known weak spot?

Other DX Head: Eroded Valve Seat But No Pin Hole in Water Sleeve.....

DX2 Head: Extra Casting Lump in the Corner

I gave it to Barry - my machine shop guy  - to assess and he concluded that to repair it he would have to cut away quite a bit of the  corner of the block.  I trusted his opinion, but didn't fancy the sound of that, so looked for another solution. I used a two part, Loctite filler product used for pump repairs and similar. It's aluminium based and resistant to high temperatures. 

With the eroded area already having been cleaned by the vapour blasting, I degreased it all down with alcohol before filling the hole - making sure the Loctite oozed out of the pin-prick hole. Following the example of the DX2 head, I built up an additional level of filler to provide added protection. The repair looked good and was invisible from outside the cylinder head.

Now nearly mid October 2017, two months had gone by since I completed the bottom of the engine. Perhaps at last I had a decent cylinder head and could get on with the rebuild!