Could also be pushrod tube seals, mangled pushrod tube or pushrod tube with a hole in.

One for Ken - this shows the difference in wall thickness between old and new.......

Ooof!
Maybe try holding a barrel up to the light, so that you can gauge how the wall thickness is reduced closer to the top.

Has anyone got a photograph of an 375 or 425 barrel, which shows how much thicker the barrel walls were?
In my opinion, that's one of the prime reasons those older engines really could be driven flat out all day, even if the timing wasn't spot on...

IMG_2929 by Robndaisy, on Flickr

425.

Made up another bucket of molasses/water mixture and dropped some rusty junk in.


The bucket had a year old solution in, which stank worse than a festival toilet!

Thanks, Rob.
not much chance of heat warping that cylinder, some proper over-engineering by Citroen in the good old days...

Yikes! Think i'll wind back the timing a tad........bastard thing has blown through one of the exhaust gaskets too and leaking from new spectacle seals grrrr.....will have to lossen off and re-seat

Took the roof off and drove to the MOT station.

It Passed!

Drove home happy...

Repaired and re painted my vent flap !

Yes I found this out the hard way. My oil feed pipes started leaking a lot with what looked like corrosion, so I bought new, and over tightened on the block end.
In the end I managed to just get away with a new banjo bolt and a new washer. I annealed the washer carefully as when I contacted Roy at Ecas he said they were a batch of quite hard ones that needed it. I snugged up the new bolt so carefully...