{"id":1553,"date":"2021-03-20T12:06:48","date_gmt":"2021-03-20T12:06:48","guid":{"rendered":"https:\/\/bxproject.co.uk\/blog\/?p=1553"},"modified":"2021-03-28T10:49:14","modified_gmt":"2021-03-28T09:49:14","slug":"citroen-bx-cylinder-head-overhaul","status":"publish","type":"post","link":"https:\/\/bxproject.co.uk\/blog\/citroen-bx-cylinder-head-overhaul\/","title":{"rendered":"Citro\u00ebn BX – Cylinder Head Overhaul"},"content":{"rendered":"<\/span> 5<\/span> min. read<\/span><\/span>\n

From the cylinder head leak testing <\/a>previously carried out, we know that we’re losing compression, largely in cylinder 3. Given how much the valves are leaking, this could be where all of the engines missing 20+ bhp are escaping. There is nothing in the engines service history to suggest head work has been carried out, but clearly, something is a miss. Can we find the reason for all this leaking pressure and overhaul the cylinder head?<\/p>\n\n\n\n

One of these valves is not like the others<\/h2>\n\n\n\n

Something I didn’t notice when I first took the head off was the ‘odd’ looking valves over cylinder 3. Unfortunately, I didn’t get a better picture before the head went to the machine shop, but hopefully, this close-up shows the difference well enough.<\/p>\n\n\n\n

\"\"
Cylinder 3 valves are not like the rest in the head<\/figcaption><\/figure>\n\n\n\n

The valves on the left are Cylinder3 valves, with cylinder 2 on the right. With a bit of cleaning is was immediately clear that the materials are different. The valves over cylinder 3 are a yellow, almost brass colour. The dimple on the bottom of the cylinder 3 valve is very different and the inlet valves are missing a relief angle. My suspicion is that this engine has dropped a belt and had new valves, but can I prove that?<\/p>\n\n\n\n

Removing the Cylinder Head Camshafts<\/h2>\n\n\n\n

To get to the valves, I need to remove the cams. This is a fairly straight forward process, well documented in the good old 0908 Haynes Manual. The only thing that worries me is warping the camshaft covers, so I’m pretty meticulous about taking the screws out in the right order. All 24 of them.<\/p>\n\n\n\n

\"D6C
D6C cylinder head laid out on the ‘bench’<\/figcaption><\/figure>\n\n\n\n

No power tools here either. These are just the sort of bolts that will turn to cheese when faced with 18v of Makita brutality. Every bolt was carefully undone by hand then the camshaft caps removed. The final result is pretty satisfying and very reminiscent of the film ‘Short Circuit’<\/p>\n\n\n\n

A note on valve spring compressors<\/h2>\n\n\n\n

Something that caused me a headache when I first took an Mi16 head apart was finding a suitable valve spring compressor. My old faithful Machine Mart spring compressor<\/a> used on countless XUD engines was too small in every way. It took a few purchases to find the right spring compressor.<\/p>\n\n\n\n

\"Mi16
Mi16 spring compressor. It took a long while to find the right one.<\/figcaption><\/figure>\n\n\n\n

The spring compressor above is the one I found that does the trick. The problem is how far the springs are from the edge of the head, largely because of the angle. This means you need a wide opening to clear the head and the long through to get down the tappet hole. This is set to 200mm max open which gives about 60mm minimum closed position, compared to the XUs 130mm max opening, this is a big difference. The Machine Mart website doesn’t seem to list this one anymore (the Laser 2609<\/a> looks similar) but the Sealey VS154 spring compressor<\/a> might do the job.<\/p>\n\n\n\n

Non-original valves<\/h2>\n\n\n\n

With the hydraulic tappets pulled out, a strong magnet is ideal, and the valve spring removed, I could finally release the valve. And immediately something stood out.<\/p>\n\n\n\n

\"'V537686'
‘V537686’ stamped into the after market BGA valve<\/figcaption><\/figure>\n\n\n\n

On top of the valve, a part number is stamped in ‘V537686’. I’ve never seen a genuine Citroen\/Peugeot valve with a part number stamped in so this is a pretty obvious sign these valves aren’t original. Looking up the part number, this is an aftermarket BGA part. And it doesn’t like it was ever ground or lapped in. Could the missing BHP simply be caused by poor engine building after a valve has bent?<\/p>\n\n\n\n

Bent Cylinder Valve From Cylinder 3<\/h2>\n\n\n\n

While the aftermarket inlet valves moved freely in the valve guides, I figured I best throw them into the lathe and see if they were straight. Before setting up with the DTI, I thought I better just spin it up incase it was visually out.<\/p>\n\n\n\n

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