Morris Minor Owners Club

Hello,

I've recently purchased a Minor 100 which I do not believe has been converted to run on unleaded.

What additive precisely do I need to buy? From where can I buy it?

If I forget, will it burn the valves out?

Apologies for the newbie questions....we all start somewhere

No additives - just set the exhaust valve gaps at 15 thou, and check/reset every 3000 miles. It will be fine.

Hi,
I used to use Castrol valve master on recommendation, it was also recommended by 'Practical Classics' I believe.
See link below, I believe Halfords also stock it.
I don't think you'll wear anything out though, unless she's in regular use and used on motorways, however get a second opinion on that, as I may be wrong.
Best wishes,
Mike.

http://www.google.com/aclk?sa=L&ai=Ckri ... type%3Dpla

waste of cash,as bmc just make sure the exhaust valve at 15thou,Have run my 55 for without additive since the change in petrol without any problems.

It's one of the biggest 'cons' around!

I think we need to be specific here. When leaded petrol was phased out there was much talk about valve seats receeding and the BMC A-series engine was thought to be one of the worst offenders. Much was written on the subject and the FHBVC tested a number of additives of which they gave their stamp of approval to about half-a-dozen, the which used about half-a-dozen different elements to provide protection from the damage. These are listed on the FHBVC website and are available widely from auto-accessory shops and elsewhere.
Many experts gave their opinions at the time, including John Rowland who was working for Silkolene Oils at the time as a chemist. John has a frogeye sprite amongst other long term motors, so is well versed in the vagaries of A-series engines - he produced a series of three articles which were widely circulated at the time and explained what happens, and how best to prevent it. His conclusion was that adding any of the additives would do your engine no harm; mixing the additives might well do your engine some harm; the additives cost money which might be better invested in eventually modifying your cylinder head IF your valve seats receeded; if you don't thrash the living daylights out of your engine the problem is unlikely to emerge (unless you are very unlucky).
Ive done about 30000 miles in TFM now on an engine that has had NOTHING done to the head and I use NO additives. There has been no sign of the valve-seats receeding and no sign of problems with the valves which are set with a gap of 15 thou. As the engine was out of a scrapper I have no idea how many miles it has done but I suspect LOTS. The Van is regularly used on long and short journeys at up to 65mph.
IF your valves receed, the first stage of reconditioning the head will include cutting out the existing seats and fitting hardened new ones, so no harm will have been done! Not only have I never heard of a valve being damaged in this situation (occasionally you hear of one having burnt out at the edge but that has nothing to do with receeding valves) but I can't remember ever having read of such a situation either.
So my advice (from experience) would be to ignore additives (unless you are going to thrash your engine) and enjoy your motoring. Check your valve gaps - BMC and Haynes recommended every 6000 miles in their service schedules - and only if they show considerable signs of closing do you need to worry about it - I do mine every 3000 miles as it doesn't take long and at the worst costs the price of a new gasket (£1.00 + vat). Having your own head converted to hardened valves and seats will cost you about the same as an exchange head (£150-200) but don't even THINK about it unless you KNOW it is necessary - I have known lots of people who have had the job done but only ONE who NEEDED it done!
Happy motoring!

Good precis - I'll just add - if/when fitting hardened seats, then the later harder exhaust valves should be fitted anyway - so don't worry about the valves either!

I too worried about this when I first got my Morris nearly 5 years ago,I did use the valvemaster additive a few times at first but having looked at the number of additives on the market at various pricesand listening to the excellent advice on here I made the decision to set the exhaust valves as BMC suggested to 15 and use the car without one.
I have not noticed any loss in performance or had any problem and I am doing a round trip of approx 26 miles every workday down the M6 doing approx 60 MPH. There might be marginally more engine noise because of the valve gap being wider but its not significant, therfore, I would say save your money and use it for something you need or can make motoring simpler like electronic ignition

I used to use mine doing around 15000 miles a year urban and motorway and never used any additive and it was fine

What is the point of setting clearances to 15thou if the seats don't recede? I'm running the proper clearance and so far no problem.

Two reasons - the unleaded fuel burns hotter, so the exhaust valves will be hotter and will expand more, closing the gap. MG/Rover raised the gaps to 15 thou round about the time of unleaded introduction. It also gives that tiny bit of extra lee-way if the valves DO recede into the head slightly. As soon as the gap reduces to zero - possibly only when the engine is working hard (ie may not be seen when checking) then the seat and valve are toast..... In fact I run mine at 18 thou these days. There is no performance loss and I feel it helps to prevent a 'backfire' that I have had in the past in hot weather when the engine is working really hard on a long M/way incline - with a loaded up car! Most important though is the 3000 mile check and reset.

The only 15 thou clearance I know of from mg/rover is the one specified on the mg Metro, and I presume that is cam related. I can see the expansion point of view, although I thought expansion reached a certain point and no more, after that things melt.

It was the standard for all 998 and 1275 unleaded engines Les. Metal expansion is linear with temperature - the valves are (hopefully) well away from melting! But feel free to use 12 thou if you wish!

les wrote:What is the point of setting clearances to 15thou if the seats don't recede? I'm running the proper clearance and so far no problem.

Exactly, "15 thou" is a bit of a myth and a potentially damaging one at that! As an experiment, I tried my convertible exhaust valves at 15 thou and the result was a more rattly top end and taking the edge off the performance.

The manual says 12 thou for a reason. and extra 3 thou will do nothing to make up for the lack of unleaded.

We've been over this before = CJ keeps dragging up 'the manual' - which was written a long long time ago when the fuel was a very different composition to todays unleaded brew. MG/Rover made the change for good reason. It didn't make the slightest difference to my engine's performance - I defy anyone to quantify any power reduction from a 3 thou loss of exhaust valve lift! It also made not a jot of difference to my engine noise - not even when I went up to 18 thou! But as I say - use 12 thou if you wish - it's your engine...... Do you also run SAE 30 oil in your engine, I wonder??