Morris Minor Owners Club

Hello again hope as I,m sure you will help in identifying the problem I have with my morris minor engine, a couple of years ago I bought a second hand engine from a morris dealer I was told it was a good runner but it was blowing blue smoke which should clear because it had been standing awhile, anyway it did,nt clear and i decided after taking advice from various people that it was probably valves seals etc, I removed the head had it skimmed and new hardend inserts fitted and all ground in and head refitted guess what ,yes still got the dreaded blue smoke the point I,m leading up to is could it be piston rings or pistons themselves to change how can I tell and is it fairly simple to do this job ps I tested the compression on all four pistons and found from number one 162 158 156 164 after putting in a few sqirts of oil the compression went up but not by much looking forward to any advice

From what you describe it is more than likely pistons and or rings.
Replacing the pistons/rings is a reasonably easy job - the problem lies in what the bore is like.
A rough guide - If when running your finger nail up the bore it is stopped by a wear ridge that is a good indication that the engine needs a re-bore - and new oversize pistons - again a reasonable job but you will have to have the engine out and a strip down and taken to an engine reconditioning / re-boring specialist - when you strip the engine you may find that the rest of the engine needs work i.e. crank reground/new shells etc etc .
May be better to find a short engine in good condition.
Phil

Simple test - with hot engine after a good run, remove the oil filler cap and rev it up. Is there a plume of smoke/fume from the rocker cover? New rings may be worth a try - if the pistons are damaged then a rebore is a better idea than putting new pistons in worn bores. But first - check the crankcase breather pipes are clear, if there is crankcase pressure due to poor breathing it can push oil up past the rings. Your compression readings are not too bad. When the head was overhauled - did they fit the later type guides (did they change them at all??) with the much more effective 'top hat' seals on the inlet guides?? You can see these - if fitted -if you take the rocker cover off.

Thanks to Philthehill and bmcecosse for your prompt reply to my problem, having just removed the head and had it skimmed and made unleaded I am going to keep using it until the weather gets worse than it is now and then put it in dock and check out the rings and pistons as you suggested this is my first attempt at engine rebuild although I did do the head with the help of my son and feel a bit more confident I,ll keep you posted about the outcome thanks again !!

PS bmcecosse I did check for abnormal engine pressure but found no smoke from oil filler cap! thanks

Well - should mean the rings and pistons are pretty good !

Blow-by at no load will tell you when it is well past time for overhaul. What it will not tell you is load under pressure, or whether the oil control rings are not funcioning correctly.

Plug electrode inspection may indicate oil coming past the rings. The rings may be sealing reasonably, but with side clearance, allowing oil be passed. It may be worse on one cylinder than the others, so you really need to consider all the options. Your valve stem condition, when dismantling previously, might well have indicated oil burning onto the stems.

PTH is well on the money. Fixing the top end may well apply extra loads on the bottom end and accelerate wear in that area. Loose bearings can mean too much oil being thrown around the crank case, even if the pressure is OK.

Bores need checking for ovality and taper, as well as the simpler measurements, if considering re-ringing.

Do seek advice on your engine condition, if you are not entirely sure, when it comes to overhauling. Things can easily be overlooked.

RAB

Thanks for the replies regarding problems with engine and blue smoke after and also prior to having head removed and made unleaded at the time I did,nt check bores for wear, Big Mistake !! I was somehow confident it was the valves and guides etc when I saw the state of them one with broken edge and others covered in grey type carbon anyway took head to motor engine refurbishers and had all the necessary work done new valves springs seals and valve guides fitted but now I fear it,s a stripdown again to check the rings and piston bores I rechecked the carb yesterday after finding the plugs all sooted up I cleaned them off and rechecked the gaps the carb was running rich as going by the book removing the air intake and lifting the needle valve a fraction would this be the culprit perhaps before a stripdown! will go out today to try it out wish me luck!!

I would check everything before stripping.
Check the float level - see manual for details.
Check that the piston falls with a nice clunk.
The mixture should be right when lifting the piston (with the piston lift pin) slightly the engine speeds up and then dies down.
Plugs should be a nice biscuit colour when the mixture is right.
Phil