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[Bigron]

http://www.ebay.co.uk/itm/351125980613?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

What do you think, gents  anyone got any experience of it?

Ron.

[GastronomicKleptomaniac]

Magic beans painted silver

[aaronjb]

Seen them for sale every year at the Classic Car shows so .. someone must buy them, I guess!

[frostbite]

They look like lead baubles

[BazaJT]

These things have been on the go for years!Personally never been tempted to try them so whether they work or not I can't say.Ask yourself the question "Do I feel lucky?"

[STEMO]

These things have been on the go for years!Personally never been tempted to try them so whether they work or not I can't say.Ask yourself the question "Do I feel lucky?"

Why would you be tempted? Have you had cars that were designed for leaded? Old git.

[BazaJT]

Yes Stemo I am an old git I'd say I've had more cars designed and built to run on 4 star than on unleaded

[STEMO]

Yes Stemo I am an old git I'd say I've had more cars designed and built to run on 4 star than on unleaded

Yes, but 4 star would be available then.

[Bigron]

STEMO, I confess to being in the old git/fart category too, but my interest centres on my old Sunbeam S* which I have mentioned on here more than once. Born in 1952, it will have fairly soft valve seats and a desire for leaded petrol, so when I get a Round Tuit I will re-assmble it from its many component parts and be looking for either a lead supplement or obtaining hardened seats.

Ron.

[STEMO]

STEMO, I confess to being in the old git/fart category too, but my interest centres on my old Sunbeam S* which I have mentioned on here more than once. Born in 1952, it will have fairly soft valve seats and a desire for leaded petrol, so when I get a Round Tuit I will re-assmble it from its many component parts and be looking for either a lead supplement or obtaining hardened seats.

Ron.

Supplement every time, Ron, surely? But I wouldn't trust these little fellas to do the job, I'd be using a proprietary (proven) brand.

[Andy H]

Snake oil.

How many miles a year will you ever realistically ride it?

Unless your cylinder head is new/old stock and never got exposed to leaded petrol the existing valve seats will outlast you.

[Bigron]

Definitely not new, Andy, so that's good to hear. You are saying that the mileage it has done way back in the days of leaded petrol has given it residual "lubrication"?
I am given to understand that valve seats are only part of the problem, the other part being valve stem lubrication, which is why more modern cars (i.e. from the unleadedd era) have had to have larger stem/guide clearances to compensate for the lack of lead-derived lubrication.....and the consequent increased oil consumption?

Ron.

[Andy H]

A key cause of valve seat recession is the tendency of a hot valve and seat to weld themselves together and then for the seat to be eaten away as little bits get pulled off

Tetraethyl lead was originally added to petrol to improve the octane rating and allow higher compression ratio without pinking / pre-ignition. A side benefit was that the lead binds with the metal of the valve seats and somehow acts to prevent the valve and seat from welding together.

I am puzzled by the reference to looser valve clearences on modern engines My experience of engine rebuilds is limited to1960's Royal Enfields (pushrod) 1980's Suzukis (DOHC) 1970/80s Rover V8 (pushrod) and my 1994 Omega 2.5 V6 (Quad cam). Generally the oldest engines had big valve stems with massive clearances and the newest engines have dainty little precision machined valve stems  AndyB or Marks DTM might be able to throw some more light on that one

[Bigron]

My information on the clearance issue came from a well-respected engineer who managed/maintained a large fleet of vehicles in London and also did major oil testing and research (Duckham's Q scored very highly), so I assumed that he  was speaking with authority. His concern over the increased oil consumption was very real, with all of those vehicles to cater for!
I am happy to listen to other views, obviously, as the wisdom on here is phenominal. 

Ron.

[Andy H]

My Royal Enfields and Rover V8s didn't have oil seals on the valve stems. They burned almost as much oil as petrol 

The Suzukis and Omega V6s have oil seals on the valve stems which are then protected from oil spray because they are hiding under the cam followers.

I don't know what the arrangement is in an S8 Is it single cam with rockers actuating the valves?

Either way I can't see how the petrol formulation will have much effect on the valve stems Of more concern is exhaust emissions due to burning oil leaking past big clearances on the valve stems.........