Unleaded Petrol

[ssorthiek]

It’s very difficult to get leaded petrol these days and I was wondering whether you can use unleaded petrol in a Jap 4/3 engine. I seem to recall that older engines ran on unleaded petrol anyway and that leaded petrol was introduced later until it was found that it was environmentally damaging.

If the standard JAP 4/3 engine cannot run on unleaded, can the valves be replaced by hardened valves at all or do we need to used additive?

Any advice would be most welcome.

Keith.

[wristpin]

I think that your engine would have been produced in the leaded fuel era but unless you are going to work it hard and hot it is unlikely to come to any harm. If you are concerned there are various lead substitutes available from Halfords etc .
As well as its anti knock properties the added lead provided some protection against valve and valve seat recession – particularly where the valve seats were cut directly into cast iron cylinder blocks. However for casual use unleaded is unlikely to cause any harm, but if you are concerned go the lead substitute route.

[ssorthiek]

Thanks wristpin, that is most useful. It’s been something that has been bothering me about older engines in general and I’ll probably look for some additive before running my new Coleby in anger but that won’t be until next year now.

I suspect that adding the additive to a lead free engine won’t do that any harm either in modern lawnmower, but views on this will also be welcome. If I can get away with it I only really want to use one petrol can for everything.

Keith

[trusty220]

I can confirm what Angus says is true- I’ve been using unleaded fuel in a JAP 6 on my Trusty for nearly twenty years doing ploughing matches and generally pottering about at shows. It doesn’t get hot or overworked and so the valve seat recession isn’t an issue- at least it hasn’t been up to now.

I don’t use a lead substitute either, but if I see the valve gaps closing up that will be my first course of action.

[charlie]

Plenty of information about fuel on the FBHVC website Another issue with modern fuel is the ethanol content and how it can degrade certain materials eg cork and rubber, also water accumalation.

[ssorthiek]

Thanks gents for the replies, it is very much appreciated and all well worth knowing, especially the effects on other component parts which is probably often overlooked. I’ll be looking at the FBHVC website in more detail to work out the water accumulation issue since I don’t really understand this at the moment, but leave it with me, it’s all interesting stuff to get my head around.

The people on this site certainly has a wealth of information all eager to impart on new members and a heartfelt thanks for this.

Keith

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