Morris Minor Owners Club

I don't think so, if the noise stops when there is no combustion as the valve train is under the same stresses with or without combustion, certainly at tickover anyway. Could it be a broken piston ring?? Without hearing the noise it's difficult to tell.

or the exhaust gasket ;-)

but yes - if the noise goes when not firing it is probably something major as Cam suggested
the load on the rockers isn't hugely changed without a spark (the load on #8 rocker will be slightly lower)

To prove that out, you could remove all the clearance from the rockers and see if the noise is there (don't run for long!). if there is a noise even with no clearance it really isn't likely to be cam follower / rockers!
Bear in mind that it may be a bit more poppy if you go too far as it will leak burning gasses to the exhaust and inlet.

Whip the head off, take the sump off, undo the big end cap and push the piston out of the top, I'm sure all will become clear. Not too big a job to reassemble afterwards, just confusing if you don't find anything.

Well Cam,where have you been ,when all this has been going on? YOU WERE BANG ON!!!! LOL Spoke to the firm who supplied eng. to B Motif -Kar Engine Servs . he straight away said no4 piston mishaped in bore ! At 3.30 this pm ,he cagoled me into removing the head ,by 4.30 I was 'phoning him with size of replacement piston! Bore seems ok,but has polished areas ,and a deeper mark near base of piston . will get piston out tamara . He was'nt very happy about me taking the engine to about 5,500 rpm though! Another £50! Iam seriously considering going for a larger engine next year . Will let you know how I get on with new piston . Gotta have it done by Sunday for A35 Nat Rally

Right, so I assume the piston itself was oval?? has this been caused or was it a defect originally in the piston?

Polished bore areas.........hmmm that's not too good for the new rings to bed in. Maybe a quick hone with one of the 'spider leg' type honing tools that fit into your drill?? Just to remove the glaze??

Also if it has 'spots' of polished area then have you checked to see if the bore is uniform?? i.e. not worn oval too?

What's the history behind this engine anyway? How many miles has it done since it's rebuild? Also what pistons are you using?

In my Mini 1293 I used Hepolite pistons (about £60 a set) with a CR of 10:1 and I used to take it up to 7000 RPM no problem. In my 1380 now I am using Omega pistons (£280 a set) with 10:1 CR and they are fine. I think it's quite important to use good quality pistons, but why is your chap not happy with 5500 RPM?? Surely that's more to do with bearings and balancing than pistons?? And 5500 is OK for a 1098. I once knew a chap with a 970S race engine that managed 10000 RPM!!

Would be nice to know WHY your piston went oval though!

they might have been oval to start with!

Would be nice to know WHY your piston went oval though

they might have been oval to start with!

I thought that too - Especially as the engine guy jumped to that conclusion immediately. Maybe he had a batch of poor pistons and it's not the first time he's heard complaints. It make take time for the rings etc.. to loosen up enough for the piston to slap about.
If it was a faulty piston - it would be a cheek to charge another £50

I had the same thing on my pickup, thought it was followers because I'd checked everything else, but it wasn't!
Mine seemed to only appear after a minute or so of running, presumably due to oil getting warm. Never found problem (car is currently off the road), but I've heard that the rockers / shaft can wear causing a tapping noise.

Ben

but I've heard that the rockers / shaft can wear causing a tapping noise.

Very much so, but it was the fact that the noise went when the spark lead was removed that sounded alarm bells in the piston/rod direction.......

Thanks for everyones comments ,I take on board all your points . The way I see it is,the eng. had a guarantee (which ran out about 3 months ago) plus I have done stuff -new cam etc ,which I consider to put the guarantee void . I'm not too happy about paying out any money ,obviously,but I'll just put it down to experience .If the repair turns out ok ,I'll either keep the revs down in general ,or maybe get a bigger engine built (poss. another 1098 with balanced bottom end ,and wilder cam ,that way I can use my 12g head and some other bits I already have . Question is ,just how far do you go to keep it an everyday drive,and not get the general running probs associated with tuned engines . I 've learnt my lesson now!

Forgot to say...................The guy reckoned it was also due to heat build up ,considering it was close to the bulkhead ,with less airflow . I think he has a point. Ah well ,experience is a great thing!

due to heat build up ,considering it was close to the bulkhead ,with less airflow

Maybe on an engine without much space around it, but doubtful on a Minor.

We have the occasional piston slap complaint through here with modern cars, but it's always when cold & improves with heat.
If your problem is there when hot or cold, it might be a cracked piston or a damaged conrod little/big end bearing as suggested.

Good to see you've at least narrowed it down to one particular cylinder.

due to heat build up ,considering it was close to the bulkhead ,with less airflow

all cylinders have a water jacket around them so he's talking nonsense. I guess he was just trying to avoid taking any blame - good pistons don't go out of shape.
Anyway - the mosty important bit is that you get back on the road to have fun.. that's what these things are for right?

Took my 4 door in for its retest this lunchtime. It got there fine if you will ignore that it developed a serious missfire, ran out of petrol, and another earth packed up on the front lights.
I hotwired the earth at the roadside (ripped out the wire, bared the end and used 2 washewrs and a self tapping screw )
I dashed beck to my other minor and filled a petrol can off the pipe to the carb (by yanking it off the carb with a sharp tug :lol)
The missfire will have to stay until, it comes back... I've laready fixed 2 problems that caused missfires maybe it's something a bit more wierd - I guess it is scared of going on the road as it's been an angel for the last 10 days and only decides to play up when it is pointed towards the MOT station. blumming cars

blumming cars

Youre right there Ray! A guy up the road commented on how nice it was to see cars like mine /ours on the road ,my reply was "it's a labour of love ,mate ,today I hate this car cos its running rough (ticking),when I find the fault and cure it ,I'll be happy&smiling all day long !!!! " You probably know more than I about cars,Ray,but have you thought about :mis fire due to cracked dist. cap/crack in coil bakelite /my rotor arm crack/dodgy plug lead to cap or dist connection /loose wire to dist cap to coil ? ROD

Erm, I don't know where all the posts came from, but they weren't there when I sent my first reply! Now I feel a bit daft!

cracked dist. cap/crack in coil bakelite /my rotor arm crack/dodgy plug lead to cap or dist connection /loose wire to dist cap to coil

yes - changed all that and it didn't help followed by changing the condenser and points (old points were fine) then it ran fine for 10 days...
If I can't see anything obvious I will try another new condenser just in case the new one has failed (not difficult to do - you can fit the new one on the outside as a quick test). then I'll change all the other bits over from Riley as I know he is working fine.
and if it still missfires, maybe theres a poor conection between the timing plate (the bit that the points screw on to) and ground.

Yeah That wire to ground is very fine and easily damaged .What about a plug breaking down(crack in porcelain getting damp/wet?)I find sometimes just fitting new set of plugs helps to run smoother ,even though the originals seem /look fine .

BACK TO ORIGINAL 'ticking advice ' POSTING ...New piston now fitted ,all seems ok ,been for a short drive ,no ticking . Going to A35 nats tomorrow ,so will get some miles in to see wot happens .

Good news mate! Keep us posted.............

A 70 mile run with new piston !all seems ok -keeping revs down to 3000 is a pain though!