Fuel Additives?

[roscobbc]

aw51 121565 said:

FBHVC's tests in the very early 2000s may disagree - they used a series of unadapted A-series engines; their exhaust valve seats collapsed when neat unleaded was used while other test A-series engines' exhaust valve seats survived to varying degrees depending on the particular additive used (leading to FBHVC's now-historical recommendations of unleaded additives)...

Oh, and pinking (and reduction thereof by using unleaded additives resulting in higher octane fuel as suggested upthread ) has nothing to do with exhaust seat recession (and the higher resulting octane assertion is unmitigated bocks also), btw.

Remembering back in the day - the 'A' series engine always seemed prone to valve problems - more so I would have thought that any other 'cooking' 50's or 60's engines - so as a 'worst case scenario' engine in terms of comparative testing of fuel additives, yes ideal (perhaps) - in reality the 'A' series would not be a representative choice to use, simply because most other engines from the same period would cope quite well with unleaded fuel.

[b2hbm]

roscobbc said:

Remembering back in the day - the 'A' series engine always seemed prone to valve problems - more so I would have thought that any other 'cooking' 50's or 60's engines - so as a 'worst case scenario' engine in terms of comparative testing of fuel additives, yes ideal (perhaps) - in reality the 'A' series would not be a representative choice to use, simply because most other engines from the same period would cope quite well with unleaded fuel.

Given how many A series engines were around in those days I wouldn't argue with the choice of engine, but you're right when you say it's not a "one size fits all" test. IIRC the test included 20hrs at full throttle & load to show accelerated wear and 20hrs was roughly 1/3rd of the total test, much harder than real life for most engines.

But the original remit was to rank the additives on the market and in simple terms of providing a league table, it's fine. The test wasn't designed to prove you need them in every engine on the market, but that's the way it was and still is interpreted. All it proves is that if you have an A series engine and want to drive it hard, you need one of those VSR additives.

The other aspect was that they used brand new heads & valves, freshly ground in. I'm not sure about the "lead memory" or "one tank of leaded in four" theories we've see bandied about but I can understand work hardening of a few thousand miles in service prior to going full load. I've often wondered if the real tale is that an engine run in at low loads even on unleaded petrol would actually be ok for 90% of normal users.

[wildoliver]

My advice is always the same, sometimes listened to but often ignored.

On MGs be it a Midget, B (or non twincam A) or C it is a total waste of money to use additives, I've done literally hundreds of thousands of miles now since leaded fuel disappeared in Midget 1275s, 1500s, MGBs and a couple of MGCs. None of those and they get driven damn hard have suffered recession, some cars have done more mileage than others but most have done well over 20k and one of my Bs I've taken round the clock, a mixture of road and motorsport use across them too.

If I'd used additives it would have cost thousands, but worse case scenario a head could have been pulled off and converted for a few hundred.

My advice - doing loads of miles and driving the arse off it.... Take a chance, worst case scenario and you get recession go and get the head converted and do the job right = selling point later on and no pratting around with an additive that may or may not work.

Do very few miles.... Take the risk you will be very unlucky if anything goes wrong and if it does converting the head is cheap anyway.

I wouldn't trust an additive actually does anything other than provide a warm fuzzy feeling for the owner. Hardened inserts are the only way to be sure but I have my doubts most classics really need them, certainly it's pretty pointless to fit them before minor seat recession occurs.

[caziques]

The one aspect that can't be controlled (with regards to valve seat recession), is how hot the mold was when the head was originally cast.

Cold molds would result in chilling, which leads to harder material. Warms molds mean larger grains in the material which are softer.

There were generally better valve materials used after the first US emissions hit in 1967.

[fatjon]

aw51 121565 said:

FBHVC's tests in the very early 2000s may disagree - they used a series of unadapted A-series engines; their exhaust valve seats collapsed when neat unleaded was used while other test A-series engines' exhaust valve seats survived to varying degrees depending on the particular additive used (leading to FBHVC's now-historical recommendations of unleaded additives)...

Oh, and pinking (and reduction thereof by using unleaded additives resulting in higher octane fuel as suggested upthread ) has nothing to do with exhaust seat recession (and the higher resulting octane assertion is unmitigated bocks also), btw.

Jesus, you really do wear your ignorance as a badge don't you. Go read a book and then come back when you have some facts between your ears. There are numerous additives used in fuel to increase the RON. They are well known, well tested and well documented by chemists and the SAE, such as MMT (Methylcyclopentadienyl manganese tricarbonyl) and Toluene to name but two. They are also the same ones used in your additives for this exact purpose.
Are you seriously contending that TEL is the only compound in the history of the universe that increases the RON of petrol? The reason TEL was used historically is that unlike all the others it ALSO reduces the tendency of the valve to micro weld to the seat in extreme conditions. No other non toxic replacement has been found to replace this particular aspect of its chemistry it which is why seat materials have changed to allow the reliable use of unleaded.

https://en.wikipedia.org/wiki/Antiknock_agent



And as for the FBHVC, so what? A federation of historic car clubs with and agenda and no peer review once tested some A series and engines and some damaged their valve seats on unleaded. Many others have tested the same and found quite different results in normal usage.
Here is some real peer reviewed research into the subject rather than cobblers from a pressure group with the hump about unleaded being phased out.

http://papers.sae.org/730013/

To deal with your third crock.

"Valve seat recession is not caused by pinking". Pinking is a scale ranging from a light tinkle to massive and immediately destructive detonation and neither will do your valve seats or big ends any favours. Put a valve on its seat, apply a blow torch to get it all good and hot and then hit it into the seat with a hammer sufficiently hard to simulate medium strength detonation. Do that 20 times a second for a hour or two and see how the seat looks. You will find it it pretty good shape but a few though lower that it was. That is recession, seat damage due to micro welding is subtly different. The valve tears off bits of seat until the seal is gone then leaking valve and seat burn up as the escaping hot gasses are forced through the gaps on each firing cycle. No current additives will fix that which is why they don't claim to. As with seat recession it depends on the particular engine and how it is used. If you don't have a problem you have nothing to worry about. Watch the valve clearances and if the hold up you will be fine. Recession is caused by knock, additives will reduce knock by increasing the RON but if you have no pinking or detonation you gain nothing, seat damage is caused by heat and micro welds, additives will not fix that.