There's a lot of confusion about Lead & soft seats. I don't know how to tell if you've got hardened seats (apart from asking the builder), but would somebody fit soft seats these days?
The seat material should have no effect on pinging (unless it starts glowing red!). Hardened seats prevent seat wear that occurs due to the higher temps encountered when using unleaded fuel. What happens with soft seats is that the valve closes at high speed & can micro weld itself to the seat if the temp is high enough. When the valve opens again, the tiny weld is broken & transfers a very small amount of metal. Over time this metal transfer causes the seat to wear. That's the theory we were all repeatedly told when leaded fuel was phased out here in 2000(?). People were then taking apart perfectly good engines & getting hardened seats (Stellite?) fitted on both inlet & exhaust at $75 per seat. As recession is only a problem on exhaust seats (the inlet run a lot cooler), & the hard seat lobby were saying that both seats should be changed, some of us were very suspicious &, after much research, decided to stick with what we've got. So far I've not heard of one single verifyable case of people getting valve seat wear due to running on unleaded fuel. Plenty of problems with pinging & engine damage due to higher running temps though
If you have got soft seats & need to use lead then you don't need it every tank of fuel as the valves & seats retain a "lead memory" where a thin layer of lead covers the seating face of each. The layer of lead gives a "cushion" effect which prevents micro welds from forming.
The engine I run that should have leaded fuel is air cooled (so the valves & seats could be argued to be a lot hotter than a water cooled engine) & after frequent, long high speed runs where it's got very hot (hotter than it ever did with leaded fuel) there is no hint of any valve seat recession.
If anybody has had problems with seat recession due to unleaded fuel, then I'd like to hear about it as all the info I can find on the subject comes from vested interests ie. the enviromentalists (& government), the people who want to charge me for changing my seats or the people selling fuel "catalysts" which look like lumps of metal that you drop into your fuel tank!
I'd just run it on normal fuel. If you're really worried about it then drop the occasional dose of leaded fuel in it (not lead replacement such as potassium, manganese, etc).
Paul
