Smoking exhaust

[Robert Clifford-Wing]

For a while I have been adding a small amount of Kerosine to our 3 litre, 3 litres per 72 litre tank of petrol. This equates to 4% additive. Recently I changed to the same quantity of diesel instead of Kerosine. I am told diesel is 40 second oil when compared to Kerosine at 28. I have continued to add a lead additive as I normally do.

Coincidently the exhaust has started to emit a light coloured smoke, even when the engine is at operating temperature. This might of course be symptomatic of another issue.

Does anyone have experience of adding other fuels to petrol to reduce the octane rating?

I have yet to carry out a compression test to rule out a damaged or broken piston ring but as the engine has done only 4500 miles since a top end rebuild and rebore, I am thinking this is unlikely. There is no water or oil loss and performance remains as normal.

What to members think?

[Robert Craven]

Why have you been adding diesel or kerosene? If it's only to reduce the octane rating, does it matter if it's higher than the car needs?

[Robert Clifford-Wing]

It was an experiment that perhaps was ill advised?

[Dan Suskin]

Why do you add a lead additive?

[Robert Clifford-Wing]

In the hope of protecting the valve guides and seats? For the sake of the cost it seemed sensible but I could be persuaded otherwise.

[Chris Card]

As I understand it, when experimentfs were done, using a BMC "A" series engine, valve seat recession only started to become apparent at engine speeds of over 3000 rpm. A rare event with my 4.5L!

I am open to correctionon on the above.

Chris

[Robert Clifford-Wing]

[Christopher Carnley]

Diesel (Gas) oil is 35 second on the Redwood scale, ie it takes 35 seconds for measured amount to run through a specific hole size into a lower tank.

You can safely add 20% kerosene, a little smokey,but it has only a slight lubricating effect, unlike the 35 second oil, which is the cause of the smoke.

Upper cylinder lubricants have little effect even when injected directly into the inlet manifold.

[Robert Clifford-Wing]

[Robert Craven]

I've always used a lead additive (except for a short period when there was a local leaded supplier) simply because it's relatively easy and cheap so I do it "just in case" it's useful.
But when the engine was last dismantled I was told there was no sign of anything untoward.
I don't think leaded petrol was in use in the early 1920s but on the other hand decarbonisation seems to have been fairly frequent and must have been a chore.

[Dan Suskin]

Leaded petrol did not come until the 1930's. These cars were never intended to run with lead, so there is no value in adding it.

As for upper cylinder lubricants - when I remember I do add them as I've had instances of stuck valves (Silver Ghost) that appear to be reduced when using a lubricant - but I have no real data to support that.

Really, fuels require no additives - the petroleum companies have far more resources than almost anyone, and if there really was some magic ingredient, they would be using it too.

Storing the car is a different matter - then there are very useful additives.

[John Murch]

[Paul Spencer]

I'm surprised nobody has disagreed with Dan yet. Yes - modern fuels are the result of millions (probably billions) in research and development and are great for modern cars. That doesn't mean they are great for ours.

The cars originally ran on unleaded because that was all there was. Presumably lead was later added to petrol because it was an improvement, specifically because it was found that valve seats were wearing on cars "not intended to run with lead". Later, lead was removed for good reasons, but that was OK because engine technology (and metallurgy) had improved to the point where it was no longer necessary. I don't add a lead additive as I rarely go over 2500 rpm (yesterday's Curborough track day was an exception), and I too have read that it is unnecessary at these engine speeds.

Ethanol is another matter. At 10% levels, that is pretty much known to cause problems. Even with the current 5%, I use an additive to be safe. A VSCC member contacted several fuel companies about whether their 98 octane contained ethanol, and got different answers. I contacted Jet as that was what my local garage had at the time, and they said that theirs did and so did all the others as they all came from the same place. So someone was wrong.

[Dan Suskin]

Paul

Here in the US we've been using ethanol at 10-15% for years. Many years. Aside from what it does to rubber, there have been no problems using ethanol fuel. Hundreds of millions of cars and other vehicles are using it, old and new.

There is more misinformation related to ethanol than anything else I can think of, and it creates a prime market for magic cures.

What problems are there as a result of ethanol?

Same goes for lead. What demonstrable problems are there as a result of using lead free petrol in our old cars?

[Robert Clifford-Wing]

[Christopher Carnley]

The engines in these cars were designed well before any consideration was given to valve seat recession,seats being recut at overhaul, routinely.

TEL was conceived to reduce or eliminate pre-ignition, allowing higher compression ratios. The fuel use then consisted mainly of n-heptane from catalytically cracked naphtha, an omnibus term covering the lighter oil fractions, n-heptane burns very quickly.
The light aromatic crude distillates being tested (1919) by Harry Ricardo, for Shell (Asiatic Petroleum) , contained some amount of tri-methyl pentane, which has a slower rate of burning along with a small amount of benzene (benzol) giving a similar effect to the yet to be prepared TEL.
In the USA Thomas Midgley, along with his assistant Boyd secured funds from GM to research chemical additives and came up with TEL, eventually removing the by-products on the valves by adding ethyl bromide.

"Is it safe was the cry"? "Course it is", says Midgley, washing his hands in it!

He suffered very badly from lead poisoning before contracting polio, and strangling himself in a mobility frame, after inventing Freon,a substitute for poisonous ammonia and sulphur dioxide.

So apart from lead poisoning, holes on the ozone layer, newkiller (that is how the Yankees pronounce -nuclear) weapons, brown coal smoke clouds,and global pollution to be increased by a buffoon of a president,what have the Americans ever done for us?

Lead substitute or replacement apart from the single one with Pb in it have little or no effect.
Valve seat recession only became a problem after the presumed anti-oxidation effect of TEL was removed.

"Don,t forget the wine", "Oh yes the wine".

[Robert Craven]

I wonder how long WO expected his engines to last. Even though he trained as a railway engineer I doubt he designed for anything like 90 years, and most steam engines which are still running have had their major parts replaced or overhauled, and the racing Bentleys were always having minor and major parts replaced. The fact that the engines weren’t designed for leaded petrol doesn’t mean they can’t benefit from it or from modern lubricants and petrol (excepting possibly the ethanol). I should think the upper rev limit referred to in the results of the tests by the Federation of British Historic Vehicle Clubs should be treated with caution because it must depend on the force with which the valves and valve seats meet in the particular engines tested rather than some fixed rpm applicable to all engines.

In the 1920s and 1930s engines seem to have been overhauled far more often than the average owner would find acceptable these days, though partly perhaps because knowledgeable labour was more readily or cheaply available and partly because owners took advantage of the five year guarantee.

The factory service records for my 1924 3 Litre show frequent engine work and spare parts of a kind which over what was low mileage (it says 8334 in 1935) by today’s standards wouldn’t I think now be usual or welcome. From what I’ve seen of them the service records of other Bentleys show similar frequent work and replacement parts.


1924 rings fitted to pistons
1927 several new bearings. New pistons & rings. Decarbonised.
1929 16 new valves & guides.
1930 some new valves & guides, & piston rings.
1931 a valve guide
1932 a new crown wheel (for the diff of course) & some engine bearings & 16 new valves & guides & 6 piston rings
1934 4 gudgeon bushes. 8 piston rings
1935 new top bevels

[Robert Clifford-Wing]

[Christopher Carnley]

Original owners were never bothered about "nursing an expensive engine rebuild", they bought another car.
Some of the clearances in the Burgess designs were too close, eg the side clearance of the big ends at .002" caused the crank pin oil to overheat and the white metal in hand scraped bearings fretted.
Mind you, the English made Babbit at the time was vastly inferior to the Hoyt metals.

[John Robins]

As an ankle biter, sixty odd years back I remember "helping" Dad doing top overhauls on his Citroen Traction Avant and on Aunty Mary's Morris Minor. It seemed that a decoke every 20,000, and a full rebuild at about 60,000 was acceptable to most car owners at the time. If you had a Ford Eight or Ten the full overhaul came at about 40,000 but a factory rebuilt engine was cheap enough to remove the concern.

The received wisdom, to me at any rate, was that most of the engine wear occurred on the first cold start of the day. Garages would resonate to the rattle of bearing upon crank pin for perhaps five seconds until the treacle like Castrol XXL or later Duckhams 20/50 had been pumped around, especially it seemed in Oxford and Cambridge, the BMC B type engine being prone to this.

As said by those above, modern filtration, oils and fuels have extended engine overhaul periods well beyond the total life of most family owned cars, and the modern driver expects no need for engines to be touched, except for fluid changes. Would you put modern thin engine oil in your WO?

I doubt it.

[Christopher Carnley]

"Treacle like Castrol, or Duckhams Q20/50 (green balm)"? It must have been a very cold ice age in your neck of the woods.

Some of these Burgess/Varley engines have been substantially modernised with nitrided 3 % chrome steel crankshafts running in precision shell bearings and modern alloy pistons in high performance liners, modern gears etc etc. The modern lower viscosity mode may be quite appropriate.

[John Robins]

Compared with the watery substance which keeps the engine lubricated in modern cars, 5W/30.

[Chris Card]

Reverting to the question of ethanol, in my yoof I remember that Cleveland Discol petrol was highly regarded. Am I right in thinking that it was ethanol based?

Chris

[John Robins]

https://www.flickr.com/photos/36844288@N00/4272568348

[John Murch]

I bought my first WO in about 1974, a very rough 4.5
Researching its early history from 1927 to 1939 revealed that it had done about 400,000 miles. In the first few years of life 60,000 miles a year were covered. I can't recall how many engine rebuilds it had had, but the origional crank was well undersized and broke at the rear main. The engine continued to run, but the flywheel was stationary.

[Robert Clifford-Wing]