Morris Minor Owners Club

Hi guys, really stuck here I'm wondering if anyone can help...

My moggie has a knocking/tapping noise. After reading the forums I suspected 'pinking', so I checked if my engine was firing properly. the 2nd HT lead I pulled off, the engine did not change/judder at all so I figured I had a spark plug out.

This evening I have changed all spark plugs, distributor cap and rotor arm and still the same problem. The strange thing is, I checked the spark on the 2nd plug/lead and it has a good spark. Now I'm stumped, wondering if it's something more serious.

I'm really new to all this, just going off my manuals, common sense and the forums... So apologies if I'm being idiotic!

Thanks
Drew

You could swap leads 1 and 2 (both ends) to rule out a faulty lead. When you test for a spark on a plug it may look like a good spark in the open air but put it inside the cylinder and it may not spark so well.
Can you get a compression tester? This will show if you have a problem with no 2 cylinder.
Put your location up and someone local may volunteer to give you some assistance.
Welcome to the forum anyway.

First move - check/reset the valve gaps.... and then a compression check is next up. If you don't have a comp tester - then just 'feel' for the compression using the starting handle - with ignition OFF. Is #2 less strong?? Could be burned valve (assuming it's not just a closed up gap) - or head gasket, although this unlikely unless #1 is ALSO not firing properly - and the engine power is seriously down.

Is it a "knock" or a "tap"? Generally speaking a tapping would indicate something in the top end (valves etc) and a knock more likely down the bottom (main bearings etc). "Pinking" is more like a bunch of ball bearings rattling in a can, and is usually only heard when heavy load on the engine, pulling up a hill in high gear for example. My money would be on valves, and as he others have said check your compressions to see if they are even across all four. If No 2 is down but not the others most likely a stuck or burnt out valve.

Hi Guys,

Thank you for the help! I will check these tonight and let you know how I get on. I'm sure i can get hold of a compression tester from somewhere.

Thanks again.
Drew (in Harrow)

Hi Guys,

Bit of a delayed reply here as it took me quite a while to get everything done!
I managed to get a compression tester and I have very low pressure in 1 & 2... I was advised that it was probably piston rings so have stripped down the engine and taken the head off.
Turns out there is a break in the head gasket between 1 & 2, so perhaps that is where the issue was coming from, but will change the piston rings and big ends while i've got it all apart just to make sure!

While i've got it apart can anyone recommend anything else i may well need to change or look out for while i'm there? Valves were mentioned - should i get new ones?

Thanks

You will need to make sure that the head and block faces are completely clean, particularly between 1 and 2 cylinder, so that the new head gasket seals properly.

While you have the head off, it would be worth taking all the valves out, cleaning off any carbon deposits from the head and valve stems and then regrinding the valves back on to their seats - make sure you keep the valves in the same order. I hope you have already kept the pushrods in the right order?

The springs, collets and caps do not have to go back on the same valve, but make sure that you replace the valve stem oil seals (they will come in a 'Decoke' gasket set that you will need to do the job).

Again whilst the head is off, replace the by-pass hose from the water pump to the head - a short piece of standard heater hose does the job perfectly - new hose clips as well!

Do you know what the oil pressure was before the head gasket went? If you don't know the engine's history, then would be worth a precautionary change of big end bearings, with a new filter and new oil. Unless there is a clear need, I would be surprised if the rings need replacing, but with the head off and con rods apart, it's not much of an extra job.

To be honest, I would leave the rings and bearings well alone........unless you were aware of excessive oil consumption? Or flickering oil warning light? Whoever advised you it would be the rings ??? Low pressure on 2 adjacent cylinders..is ALWAYS head gasket..Richard has described the head overhaul perfectly - be sure to do it properly. Make sure the surfaces are spotless - light smear of grease and 'copper' faced gasket. Torque to 44 ft lbf, and retorque after the first heat cycle - and then reset the valve gaps.

This is really helpful guys, thanks very much.
I have been very anal about making sure everything is stored and labelled correctly so i can put it all back exactly where it came from so no worries there!
A friend of mine is a mechanic, he said that it was most likely the piston rings, and advised me to send my head off for inspection also, do you think thats advisable?
I'll follow your advice and let you know how i get on!
Thanks again

No need for 'inspection' that you can't do yourself anyway...and if your mate is a 'mechanic' ( ) surely he can tell you if there is any problem with it....mind you, if he thought it was 'the rings'.....

Your mate is probably used to aluminium cylinder heads which tend to warp if overheated.
Tell him this one is cast iron!