Morris Minor Owners Club

! and not quite as perky as it should be in performance.

Did a compression test.

3 of the cylinders around 140-150 psi, and one down to 63psi.

Adding oil to the cylinder made little difference. I guess thats the car running on 3 1/3 cylinders then!!

I'm guessing that its a burnt exhaust valve. Will whip the head off and have a look after Xmas!

Could just be needing the valve gap adjusted - worth checking.

Yes, sure sounds like a valve, would be interesting to know if you are using
an unleaded head or whatever??

Thanks BMC!

I adjusted the valve clearances (otherwise known as "tappets") a few days before I did the compression test, and that made no difference to the miss-fire ;(

Its a leaded head, Willie, maybe 6 yrs of LRP has trashed the seats??

Will find out in the New Year when I have more time.

If it was valve seat recession - then the gaps would have closed up - were they ok when you checked them ? Generally the recession seems to occur all round the seat - so the valve is not necessarily burned. Best to get a spare head ready and then it's just a quick swap-over.

Whipped the head the head off yesterday and no 3 cylinder exhaust valve is slightly burnt.

Ordered a new valve from ESM.

Surprisingly, the other valves and valve seats are in good condition, just a little bit of grind and they come up nice and smooth.

I'm going to treat the traveller to a few tankfulls of leaded 4-star- expensive, but I want to re-instate some of the the "lead memory".

It will only be leaded if you add Tetra-Boost - or can you still get the genuine stuff down your way ? I thought it had all gone now - just leaving the Sainsbury 4 star - which does NOT have lead in !

There are still a few stations selling the 'proper stuff'. There are two in Stoke that I know of although I don't use them, I just use unleaded with Castrol Valvemaster plus additive.

John, the lead memory won't build up just after a tankful, so if I were you I'd use unleaded with a decent additive such as Castrol Valvemaster plus.

I just use unleaded with Castrol Valvemaster plus additive.

What's the difference between Castrol Valvemaster and Castrol Valvemaster Plus... I've just been getting the normal sort.

The Valvemaster plus has an octane booster in addition to the valve protection so it sort of converts the unleaded fuel into something more like the old 4-star.

Higher octane means cooler, smoother running, more power and the engine being less prone to pinking.

Either additive will do, but for best results use the Valvemaster Plus!

You've got some wierdo engine though havn't you?

Yes I have. My engine kinda NEEDS it, but yours will like it too!

Think of it like yours likes a social drink but mine is a raging alcoholic!

No point putting higher octane fuel in a standard engine - it won't make good use of it! Modern engines with 'knock' sensors can make use of high grade fuel - but not the poor old Minor engine in standard form. Only additive that actually uses Tetra Ethyl Lead is Tetra-boost - so if you are trying to preserve a 'lead memory' that's what you should use.

You can actually buy a tetraethy lead additive!

I looked up tetra-boost- http://tetraboost.co.uk/ but it seems you can only buy it in boxes, good idea though.

Thanks for the tips guys, the exhaust valve (and some other bits I needed) have arrived, I'm thinking that maybe I should have done a bigger overhaul and replaced the springs and guides while I was at it, but.... where do you stop??? ;)

Think I'd better get out to the garage and start putting it back together.

No point putting higher octane fuel in a standard engine - it won't make good use of it!

But then my Minor handbook recommends 97 (Super) octane (IIRC) - that's higher than the standard 95 octane available as "unleaded".... and closer to the Optimax/BP version
The ignition timing should be retarded to allow for the lower octane - i.e. less power etc.

Of course, you can run an engine on 80 octane - just don't expect too much


Colin

I think in Latvia they used to sell something at about 71-76 Ron but it only worked in russian military vehicles or tractors. This was a while ago though.

bmcecosse wrote:No point putting higher octane fuel in a standard engine - it won't make good use of it!

It will run cooler, have more power and be less prone to pinking. As Colin says, it's closer to what is specified for the engine.

But running it on 95 octane fuel won't damage it either, but I prefer 97 personally.

Any of the recommended additives will do, but stick to the same one.

If the CR is standard the extra cost of 97 fuel is wasted on the engine - and up here the difference is a lot! However '4 star' at Sainsbury is only 1p more than 95 Esso - i did try a few gallons - the car ran absoutely the same, no difference at all. Only Tetra-boost has genuine LEAD in it - the others use Sodium/Potassium mixtures - and indeed there is/has been some debate whether or not they actually do any good at all. I don't use any additives in either of my A series engines - no problems so far.

I rarely bother using additives in my moggy, hasn't given any trouble yet. I don't do many miles though, and most of that is low-speed town driving. Standard petrol seems good enough too.

indeed there is/has been some debate whether or not they actually do any good at all.

I direct sir to our very own copy of the FBHVC's test of lead replacement additives: http://www.morrisminoroc.co.uk/articles ... tests.html. Perhaps when sir has taken the time to read the results sir would like to reconsider his remarks.

If you drive a high milage, high sustained speed minor, with a standard head they are a must - unless you want valve seat rescession and the associated work.

Of course, there's no point using ones that failed the test, or indeed the forecourt LRP - because there's no standard for what's in that LRP and they could add grated mozzerella and call it lead replacement. It'd've replaced the lead...