Morris Minor Owners Club

My sII was almost dying this evening, and had been running fine. I took out the plugs and they were terribly fouled, so put in another set. The improved performance was amazing, like a new car. Have been busy cleaning the oily plugs in alcohol, and scraping with diamond files, as they aren't very old.

I wonder what the cause of fouling is? The valve stems have no seals, and it's mostly been on shorter journeys, so maybe that's all it is. I remember driving to Chester, and got stuck in traffic on the ring road resulting in one plug fouling, the one near the dipstick.

Anyway, if your engine is suddenly very weak, it could be your plugs.

Is it running rich? Choke sticking on? Mine fouled up when the choke was stuck on and cut out.

The inlet valves should have stem seals. The pressure difference between what could be slightly above atmospheric (with a worn engine or poor crankcase venting) to a good vacuum when the carburettor butterfly is closed.

There are multiple causes for fouled plugs. First determine type of fouling (oil or unburned fuel), then determine the cause for that particular type.

It could be running a bit rich, but the choke works fine. Looking in through the spark plug holes the piston crowns are looking pretty oily too. The piston nearest the radiator looks the least oily, and it's plug was nearly clean, so stayed put. The engine seems to get very oily all over at the gearbox end, like the oil is running downhill, so probably the rocker box is swamped at the gearbox end and so more oil gets down the valve stems there. An annual swapping of plugs at the same time as the oil is probably a good routine for this car.

Could be that the oil channel to feed the oil back from the rocker box is clogged a bit? Will have a poke around.

The rubber o rings that come with the 803 cylinder head kit aren't much of a seal, and the rocker box vents to the intake silencer (crankcase vents straight out the push rod cover and blows steam like a steam engine ) I tried a 948 cylinder head that came with proper valve stem seals, but the performance was too poor and swapped back.

It's definitely oil on the plugs, and a coke residue.

I dont know much im afraid. Hope you get sorted quickly. Might be worth checking or improving the breathing system.

As above the valves should have valve seals of whatever type and if an 803cc head the valves should have the valve shrouds.
Whilst those little rubber rings are not perfect they do help in keeping the oil from the guides.
The oil just drains down through the head past the valve push rods - there is no dedicated oil return from the rocker area.
Check the condition of the rocker cover gasket as that could be the cause of the oil over the rear end of the engine.
If you have heavy fouling coming out of the tappet cover that is a sign that oil is getting past the rings. Oil goes up past the rings as well down past the rings.
I would suggest that an engine overhaul is due.

Thanks for your help greendefender, I am no expert and have the advantage of having the actual car to play with for the last 21 years. Diagnosing over the internet is not easy. I put in the last set of plugs a few years ago with the same symptoms back then (memory can get a bit vague). With the better performance it will get up to 50mph with the accelerator not touching the floor, so I should get the wheels balanced.

Of all the things that get the 803 running poorly, there are so many, plugs, dashpot, dizzy contact, fuel (inline filter helps with that), that it gets a bit confusing. I'm glad the engine is running better now, and i will get the rocker cover off and have a look.

Phil; I don't remember ever seeing valve shrouds and was told by Eddy Pepper, who was the MM mechanical expert for Essex branch, that they never had them (i wanted to fit better seals) so that's why he supplied me a 948 head. Thanks for the info about the oil return. I replaced the cork gasket a couple of times and could never get it to stop leaking at the box end. The engine was rebuilt with new piston rings and exhaust valves less than 5000 miles ago. It could be the rings are not right, as they are cords instead of original.

I am afraid that your expert needs to review his information.

See link below:

Item No: 54, Pt No: 2A545.

I have refurbished enough 803cc/948cc cylinder heads over the years to know that they were fitted.

http://www.moss-europe.co.uk/shop-by-mo ... 009a2.html

The seal is Item No: 53, Pt No: 2A879.

The later valve guides with the groove for the top hat seal can be fitted to both 803cc and 948cc cylinder heads with a bit of care but the guides are best shortened to the same length as the 803cc and 948cc ones.
It is best if the top hat seals are only fitted to the inlet guides as with unleaded petrol the exhaust valve stem/guide does need to have that extra bit of lubricant as the unleaded petrol is 'dry' and has no lubricating qualities.

If you are only doing low mileages the bores may have become glazed which can produce the same conditions as shot rings.

I don't think Eddy Pepper is with us any more sadly, but he was a good guy, even if he was wrong occasionally. The car only gets a few hundred miles a year use, and is a second car. When the cords were fitted it was because i had driven up north on the motorways after botching a decoke, and compression was completely gone.

If i am up to it then i will overhaul the cylinder head with stem seals. Easier to just replace the plugs once a year

Had the car out today and it's going like sh*t off a shovel, so clean plugs make a huge difference. I will not knock the 803 again. Last time i fitted tires i didnt bother with balancing weights as it wasnt likely to go over 50mph but now its willing to get up to 70 again it will have to have that done.

 it's going like sh*t off a shovel

Just think how much better, yet, if the combustion chambers were clean! You have treated the symptoms but not cured the disease! Maybe a grade hotter plug would improve the longevity of your temporary fix?

pde2000 wrote:Had the car out today and it's going like sh*t off a shovel, so clean plugs make a huge difference. I will not knock the 803 again. Last time i fitted tires i didnt bother with balancing weights as it wasnt likely to go over 50mph but now its willing to get up to 70 again it will have to have that done.

Glad the 803 is running well - I wouldn't be disappointed if you don't make 70 mph though. That would equate to over 6000 rpm with the gearing of the 803! I saw 60 mph a few times out of my 803 (before the big ends went...) but that was properly screaming!

Thanks guys, hotter plugs could be a fix. Because the car got laid up a fair time, and it was while ago that it was my only car, it's been hard to compare the original performance to what i have now. It certainly was capable of motorway speeds back when i got it. It could well be that it did 6000rpm. When going over 50mph at the moment the rear view mirror vibrates giving double vision, but it sounds happy enough.

pde2000 wrote:Thanks guys, hotter plugs could be a fix. Because the car got laid up a fair time, and it was while ago that it was my only car, it's been hard to compare the original performance to what i have now. It certainly was capable of motorway speeds back when i got it. It could well be that it did 6000rpm. When going over 50mph at the moment the rear view mirror vibrates giving double vision, but it sounds happy enough.

You'd better bank on a bottom end rebuild too if you are planning on revving an 803 that hard . 70 mph is not possible - book top speed (which was optimistic) was 62 mph. I wonder if your diff and/or engine have been replaced if you can do speeds like that.

well the diff was swapped for a 4.22 but that was a mistake and i have just swapped back to the original 5.275. It's sadly still the original engine too. When the engine is running nicely its quite a good ride.

pde2000 wrote:Had the car out today and it's going like sh*t off a shovel, so clean plugs make a huge difference now its willing to get up to 70 again

Haha, I don't think I EVER got more than about 55mph out of my 803 - and, as Liam suggests, the big ends didn't last very long after that My car had only covered 26,000miles from new when I bought it and had already received a Gold Seal engine

Took it up to 70 on the dual carriage way (downhill with a wind behind me ) and apart from vibration everything was fine. Oil pressure was very low after though. Will change the oil again, and see how that is.

Following wind ? Following hurricane more like!

Changed the oil, took it for a run, pressure through the floor and knocking like a woodpecker. Damn. Bearings worn to smithereens. At the bottom of the spent oil was pearlescent from the white metal flakes. So the rocket power was a temporary rush before the burn.

Should i attempt a rebuild, give it to a garage, swap it for another 803, or put a proper motor in it? I am sort of tempted to put a 948 in and return to the new 4.22 diff. I am about to start a proper full time job so probably wont have the time for a bit, so the poor old thing is going to sit on the drive for a while again.

Best options are rebuild your current engine or give it a 948 transplant. You'll be very lucky to find another 803 that doesn't need some sort of rebuild. If you go down the 948cc route, change the gearbox as well. The 803 box won't last long behind a bigger engine. Throw in a 4.55 diff as well. There's a few threads on here covering the pro's and cons of it and giving guidance regarding things like swapping the gearbox tails/keeping the long gearlever etc.