Classic cars forum & vehicle restoration.

[Nic Jarman]

Maybe the higher idle speed was also to enable the engine to be run a little on the lean side to help with emissions, thus promoting run on.
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1936 Morris 8 Series 1
1973 MGB roadster
1977 MG Midget 1500
Dax Rush

[47Jag]

Nic,

Yes it was.

When the Austin America (1300) came over it was fitted with an air pump which pumped air into the exhaust to provide an 'afterburner' effect. This was one way of reducing the unburned hydrocarbons to get a pass on the emision numbers. The only problem was the Yanks and Canadians would start them up and go back in for another cup of coffee on a cold morning only to find the carpets smouldering when they came back out. The exhaust would get cherry red without the airflow.

Art

[jessejazza]

[Jim.Walker]

I have always understood - perhaps wrongly - that seat recession is caused by the friction of a tapered valve closing into a tapered seat. Rather like an old fashioned vinegar bottle and stopper with ground seats. The friction on those could be so great with the steep taper that they often jammed.
The tetra-ethyl lead in the leaded petrol was deposited on the valve seats and acted as a lubricant to reduce friction and wear, although its original addition was to improve Octane Rating.
The softer cast iron seats on older vehicles suffered more than the harder, later, cast iron seats which often had "chills" in the mould to promote quicker cooling where needed for hardness.
I do not believe that "cleaner combustion" has any bearing on recession.

I still maintain that even where recession is detected it is best to take no action until the situation becomes extreme. Even opening up valve clearances every few thousand miles will enable enough savings in additives not used to pay for insert fitting WHEN necessary with probably enough left over to take a holiday!
Trouble is - I never put my savings on one side for the holiday! But maybe I still have time because my 160,000 mile Triumph engine does not need them yet!
Now it's time to be shot down again!
Jim.
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Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

[baconsdozen]

I thought the valve seat erosion was caused by the valve trying to weld itself to the seat,so called micro welding.This was supposed to allow the transfer of metal particles that then in effect ground the valves in.(I suppose pretty much in the cork and bottle fashion).
I think the truth is that there is no definitive answer as to wether valve seats on engines will recede or not on unleaded as there are just too many variables.If you use an additive and don't get recession thats fine,if you don't and still don't get recession then thats fine too.Personally for the few pence it costs I pour some in but if I forget or run out I don't lose too much sleep over it.
Regarding sulphur in diesel,I remember reading that BOSCH had said that the reduction in sulphur content had caused problems with some of their newer pumps with seals drying out and acceraled wear due to a reduction in lubricity.My memeory isn't what it was but I seem to remember that other chemicals are removed with the sulphur and these might result in the wear and seal drying issues.
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Thirty years selling imperial hand tools for old machinery(Now happily retired).

[jessejazza]