Separate barrel and Head

[DaveW]

Oh wow is me! ... Re-barrelling my Lomax.
Offside separated, with ease . The whole assembly was an easy joggle from the block, and a little lever separated the head from the barrel, leaving the barrel still in the block.
Near side whole different story, barrel separated from the block, but head stuck to barrel, after a while thought it would be easier if I took the assembly off as a whole... I now have the head and block on the bench. Gentle levering had yielded (i.e. broken) a couple of the fins off the barrel no worry; having new barrels and pistons. The head is steadfastly mated to the barrel.

As an aside:- the offside head seems to have had a helicon fitted, the tang was still present interfering with the plug!!... the plug was always a little wobbly and this was the reason for the rebuild... I reasoned if I was going to take the head of I’d get a helicoil fitted and also fit new barrels and pistons... I am also having the heads vapour ‘blasted’ at a local company.

Any thoughts/techniques for head separation would be appreciated.

[notsmartcar]

Pop it in the oven may do it

[Emzedder]

You could try the old 2 stroke de-coking trick;
Mix up a caustic soda solution and fill the head & barrel with it
( assuming that both valves are reasonably well seated, maybe stand the whole thing in a bowl; upside down of course )
if as I suspect, the head is 'stuck' to the barrel with carbon deposits, then the soak in caustic should do the trick.
Be sure to wear some good rubber gloves until you've got the components apart, then you can neutralise the caustic with clean water.
Best of luck with the rebuild

I'm not certain but I believe that the barrel has a spigot which fits the head, in which case, twisting the head whilst holding the barrel (or vice versa) would be preferable to 'levering' to separate the two, as it it less likely to break any fins on the barrel

Steve

[billdavies]

Hi,
Not too sure about Caustic Soda ...does that not attack the alloy of the head
The motorcycle plot worked on cast heads and Barrels
Bill

[Emzedder]

Good point Bill, maybe I should have explained that it would be wise to heat the whole thing first in the oven, then mix the caustic solution with boiling water and don't leave it soaking for more than 10 mins. Although in my experience less than 5 minutes is sufficient to dissolve enough of the accumulated carbon, by which time a good swill with clean water is a short enough time span to not cause too much, if any, surface corrosion on the alloy head.
However if at all unsure, then by all means try any method which might shock or loosen the pair from each other, possibly a good 'thump' with a dead blow hammer on a place where such a blow does not threaten the integrity of the components.
( IE : NOT on the fins )
It would be interesting to know how this resolves ?

In my defence, I was only proffering a suggestion which was by no means a definite solution or highly reccomended course of action, rather a "try this if all else has failed"
He did say that he was having the heads blasted anyway, which would have removed any surface discolouration promoted by the caustic solution.

[Ken Hanna]

Dave,
as Kevin (Notsmartcar) has already advised, I've usually had success by heating the lump in the oven (no more than 375F/190C).
You also need a length of wood 50mm x 50mm plus some cloth wrapping to keep it located centrally in the barrel and a lump hammer.
Whilst gripping the hot barrel using a welding gauntlet, hold the assembly over soft ground and deploy the lump hammer...
Ken
(p.s. It's usually rust which bonds the head and barrel together, not carbon. )

[DaveW]

Firstly thanks for the replies/steers.... The key to the success ... yep I've done it! .... section of wood that I planned to fit the barrel... then struck it with the 5lb lump ... nothing happened .... I heated it with an electric paint stripper lodged in the barrel and left running until I could just handle the the head ... same hammer ... nothing ... was thinking about scrapping the idea of new barrels and going for rings, but I'd need to lap the valves ... after some contortions valves were removed ... I hadn't thought that through but luckily the valves do drop out ... lapped the valves but still unhappy that the target of new barrels and pistons was not achieved.... saw on Gumtree a sledge hammer 14lbs, that'll do the trick ... very difficult to hold the assembly and manoeuvre the hammer ... wife called ... can't hold it 'firmly enough my arms just absorbed the blows ... onto e-bay there is a head for sale in Suffolk 50squids ... so buoyed up with new vigour tried again (I aways had the valves in situ)... still no go, Suffolk head seems like a possibility...overnight thought of inverting the idea and bash the wood on the floor ... tried this and quickly realized that the valves may drop and then bend... more contortions an put the valves back in (just the inner strings... easier) .... started bashing it on the floor holding the head... NOTHING save for the wood prop was falling out ... contrived a piece of guttering (plastic) and slipped/forced it down the side of the prop was now contained and didn't drop... repeated dropping (I'm sitting on the floor so as to control the decent) ... NOTHING .... back onto ebay £50 seems like a fair price ... frustration sets in now ... back into the garage, on the floor legs akimbo ... bashing progressed to throwing.. the whole assembly now bounces .. maybe 12-18 inches .. real frustration, more energetic throws ... then my now practiced hand caught the head but the barrel landed on the cushions .... time for a coffee and a celebration ... barrel and head separated
Thanks everyone .... now to ask some new questions ... see new topics

[howardjs]

"very difficult to hold the assembly and manoeuvre the hammer ... wife called" ...

Picture the scene... Frustrated 2CV engine rebuilder holding seized cylinder head in his arms while the wife wields a sledge hammer... Brave man!!

I wish I was a cartoonist...

Well done anyway..

Howard

[DaveW]

Finally I found some pictures of the heads after they had been vapour cleaned, and the pistons. I re-assembled the engine using new rings, after honing the barrels,(M8 Cap-head screws as suggested by post on here, replacing the Citroen 6mm peg ones) the pistons cleaned up and showed no signs of abuse.... all ready for my first run in July .... Thanks for all the input regarding head/barrel separation.... hopefully I won't have to revisit the problem again (ever)