Help/Advice required...Will only run on full choke, produces white smoke

[A G Wood]

Hello Tony,
If you're interested in just a quick go/no go leak test its dead easy to fabricate something from an air fitting and an old spark plug shell and look/listen for bubbles in the coolant or air leakage from the exhaust pipe or carburettor.
This is what we do 99% of the time in the professional environment, after all, if its leaking enough to affect the running of the engine, it doesn't really matter exactly how much it's leaking. In this country (at least) there's also the TK cylinder leakage tester (and imitators) where you aspirate a sample of the 'air' above the coolant through a coloured test solution and look for a colour change of the solution caused by exhaust gases escaping through the coolant.

[A7novice]

Thanks for all who have offered valuable advice regarding my problem. The damp cloth didn't make any appreciable difference, but I will lightly sand/lap the carb matting surface anyway. I have finally managed to get the head off, after quite a struggle. No obvious signs of leakage or anything to suggest a gasket fault when inspecting the gasket. However, there was a considerable amount of carbon in head and near valves, so I have removed that. I intend to replace head with new gasket Friday morning and keep my fingers crossed that it cures the problem. (domestic arrangements mean that this is the earliest chunk of free time I will have to do the job)

[Ruairidh Dunford]

I am intreged by the leak down tester. There are many very cheap sets on the market it seems. Is it worth buying one of these on fleabay or spend a bit more money on a named brand?

If you do decide to buy one there are plenty of very reasonably priced ones as you note - I spent about £20 on mine some years ago and it works perfectly. However - Peter did the same and ended up with a faulty unit so it may be the luck of the draw.

[A7novice]

Bob Culver was spot on (unfortunately !)  

When I managed to get head off, cylinders 1 and 4 looked as you would expect them (bored to +30, no significant wear lip at top of cylinder)

HOWEVER, when i examined 2 and 3 they both showed significant damage about one third way down length of cyclinder. (see attached photo)

I guess this is how the water was entering the combustion chamber.

I have pulled the engine out this afternoon, and all I need now.....is a replacement block, anyone any ideas? (I assume the current block is scrap....I wouldnt  have thoughtanything can be done to rectify it !)

Thank you Bob, without you suggesting the possibility of rusting through of cylinders, I wouldnt have thought to look for this possibility and may have replaced the head...........and still had the same problem.

I could not find the original post you mentioned regarding appearance of cylinders, perhaps you could point me to it?

[Bob Culver]

With the reduced Search I cannot now find on the old site, but someone described the tell tale pattern on bores
It is vital to distinguish cause and effect, and that the damage is due to internal rust and not accumulated water from a head gasket or crack. It is a coincidence two cylinders would rust through at the same time.
I dunno how relatively thin other parts of block are, otherwise liners a possibility although distinct doubts about robustness, esp if engine modified.
The effect of porous blocks variable. On other makes have encountered chronic overheating with few other symptoms.
Whether full of untreated water or lying about in humid conditions blocks seems to corrode similarly. Stored engines should have water entries blocked off and old blocks stored in a plastic bag.
Ensure the main bearings dosed with clean oil.