Morris Minor Owners Club

I took the head off my 1098 today cause its been blowing smoke and oiling a plug sometimes. Number 1 chamber looks quite coked up and thats the one that fouls up. Number 2 has a missing valve seal. I dont do this sort of thing often and whilst I can see there is wear in the bore I cant tell how bad!

The main mystery for me at the moment is how the valve seals work? They all sit about half way up the valve stem and look like they would just go up and down with the valve. THere is probably something obvious that i'm not seeing but how do they stop oil getting into the chambers?

Also how bad would it smoke with a missing seal and the rest worn?

Can you still get oil control rings and whats the general opinion on them?

The seals you have get pushed up the valve stems when the valves open so only have limited effect, and although I can't be sure, it seems that this fact was recognised later because 'top hat' seals were introduced, these had little oil seal type springs that hugged the valve stems through the rubber and the rubber base clipped over the guides, which I think had a groove machined around the top for this purpose. A lot of people fit these to the inlet only, in the belief that the exhausts need oil. You will have to check beforehand that the guides are different for these seals, as I cannot remember

The early seals - O rings - work ok for what they are. They form a 'seal' with the little cotters and stop excessive oil running down from the rocker arm and through the valve cap. The later top hat seals really need a locating ring on the guide to keep them in place. However - this will not be your problem - your engine is worn and needs a re-bore with new pistons. You could mess about with new rings - but a rebore will sort it properly and give you years of trouble free motoring.

However - this will not be your problem - your engine is worn and needs a re-bore with new pistons.

Ok you may well be right but I'm thinking its about £200 for pistons and rebore, then what if there is a bit of wear in the valve guides etc and what if i find the bottom end a bit worn. Things tend to run away with you and not just my imagination! I think i'm going to decoke, reseat the valves, new guides on number 1, new seals and see how it is. If its no good i'll run it in for MOT and see how much the whole project will cost. Maybe a replacement engine or even a recon is better value in the long run!

It's worth a go. But I suggest you start looking for another engine. And yes - it would almost certainly benefit from a crank re-grind with new bearings - and a new oil pump.

Bmc, you're a knowledgeable chap - mind if I ask you yet another question?
I'm about to strip the original engine for a rebore and truing up of the block. Will also be getting a new crank, bearings, pistons etc. I have a new old stock camshaft and cam followers ready to fit as well. Apart from the oil pump you have mentioned, is there any other "must replace" item that you can think of please? .

Is it a 1098 engine ? New cam and followers will be fine - new timing chain too - you could consider going to a duplex chain but not really necessary on a standard engine, however if your sprockets are worn new duplex costs hardly any more. Otherwise - crank grind + shells, and rebore + pistons and it should be like new! Think also of a new bush in the flywheel (for the gearbox first motion shaft) - and a new clutch plate and carbon thrust.

Thanks Bm
Yes, 1098 engine. Pretty well what I had decided upon. I may well change the distributor drive also, as it looks very worn. I might also add a spin-on oil filter while I'm at it! Naturally, I'll be replacing all oil seals as well as gaskets!
Thanks again for your valued advice.
PS I changed the exhaust valve settings to 15 thou, but changed back to 12, as it was then very rattly!

Go on - there's no real difference in the 'tappet' noise - it's in the mind!! If you have a better dizzy drive then use it - but I hardly think you need to buy a new one !! Since it's a 1098 engine (AEA 630 cam) - in later years Rover used exactly this cam timing and lift on the 1275 engines - BUT, they discovered that if it is timed forward by 4 degrees it gives better torque and mpg. Since you have it all in bits anyway - you may want to consider doing this. You would need an offset key (4 degrees!) from the likes of Minisport. Be sure to time it forwards the 4 degrees - and not backwards!!