Quote:
Originally Posted by seanick
Try EBAYing fuel catalyst. £26 for up to 2000cc.
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These things are a con. There are only a few vehicles that if running well on leaded fuel would then give trouble on unleaded. If you've ever tried to recut valve seats in cast Iron heads you'll know that they ARE hardened. They're work hardened by the hammering action of the valves over the years.
When unleaded fuel came in, quite a lot of the classic car mags ran 'tests' to show how much of a problem it was going to be. They usually had a head reconditioned, cutting through the work hardening and of course got seat recession.
Seat recession happens when the valve is running hot enough and the seat pressures are high enough that micro forge welding occours. You're really not going to have a problem with a low revving side valve (many of which will have been designed to run on pre-leaded fuel anyway). Some engines had very strong valve springs and ran their exhaust valves hot, even in the days of 5 star fuel and they may well need a seat conversion.
My advice has always been to wear out what you've got now before spending any money. By all means keep an eye on the valve clearances for evidence of them closing up and perhaps even put a bit of cash aside each month for the eventual unleaded exhaust seat conversion. I know of peole who've been doing this ever since leaded fuel became difficult to source. Some of them have bought a couple of cars with the money they've saved up.
My Morini motorcycles have seat inserts, but are very definitely pre-unleaded and the seats are only a good Iron grade. Some people are using a fuel additive, but I just stick to mostly V-Power. At the Club track day this month I'll be pulling 10,000 rpm at the end of the main straight as usual on the little pushrod V-twin as I've done for the last eight years. I do check the clearances from time to time, but I rarely have to actually adjust them.
If you do have a conversion done, go for a Bronze type seat material. They conduct heat very well, so they keep the valve cooler, they're an incompatible metal, so resist the micro welding and being relatively soft make valves last longer anyway. Berylliam Copper used to be the best seat material, but Berylliam dust is a known cancer causing agent so there were heath issues involved in the machining process. Trojan from Collumbia Metals (they also produce Colsibro popular for valve guides) is the modern choice. Stainless steel valves are not compatible with Iron guides and you risk a seized valve. There are two piece valves available and also ones with plated stems, but bronze guides are really the way to go.
Take a look around on Guy Croft's website/forum for more information.
Unleaded head or not?
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