Iron Heads...do we need lead additive in petrol?

My understanding has always been that Iron heads needed the hardened seats fitted or an additive used with unleaded. Alloy heads came with the hard seats and can be used with unleaded no additive .

Previously les_howard wrote:

Sorry if this fact is now commonly known, but I am still unsure. What has confused me is that I was told recently that valve seat recession in old engines with cast iron heads using non-leaded petrol is a myth and they don't wear any faster than before. What is the general consensus nowadays please?. I have several bottles (same make) to hand and will use perhaps half the recommended dose in the petrol, but what amounts, if any, do other members here use? Thanks....Les

Les...in my experience, it seems that it depends on how many miles a year you intend to ride. I've ridden 2-3000 miles on non-hard valve seats and I have yet to see any reduction in the valve clearances. On strip-down no abnormal wear or erosion has taken place on valves or seats. Perhaps if you ride 10,000 to 15,000 miles maybe its a different story.

Cheers Colin

Colin, it will mostly depend how hard you ride, probably of more significance than the mileage. (Why leaded E0 fuel for racing is available in bulk) If you have been running on leaded petrol for a significant amount of time then that will offer protection (Memory) for quite a while depending how hard you ride.

Les,

Yes I experienced significant valve seat recession with a cast iron head (TEA Grey Fergie) which after adjusting valve clearances again I have had no further recession since using an additive.

Again, as previously mentioned, it seems to depend on how the engine is used to some extent. The Fergie was often used at high revs for ploughing, slashing and trenching.

regards

When unleaded first appeared, testing was done on valve seat recession. Recession only started at revs above 3,000. I suspect the Grey Fergie wasn't quite revving at such dizzying speeds! I run iron-headed Land Rovers (series 1 & 3) & BSAs (A7 & B31) and a couple of tractors and have donefor many years. The A7 in particular frequently exceeds 3,000 rpm by a fair old margin. I don't use any additive and I have had no valve seat recession on any of these machines. Doesn't meanto say it can't happen though.I do ride my alloy head Norton too!

Un leaded fuel now has a lower octane level than back in the day when our machines thundered the streets unless you use the higher octane used for performance cars etc...not recommended guys! It is designed for max burn and despite the lower octane actually burns hotter, cleaner and drier. Our bikes were designed to run on a slightly higher octane and the lead helped as a lubricant and a stabiliser, hence exhaust was not clean.

Continued running of a cast head with none hardened valve seats will result in localised "pitting" around the interface of valve to head, this leads to lower performance and eventually, over time, burns away the valve seat. Valves sticking also is a problem as not well lubricated with modern fuel. Ethanol and Methanol also were not around then and believe it or not will damage an older machine more than the lack of lead will as it eats rubber and gums up if left stood. Texaco is your best fuel as they only use minimal amounts. My friend swears by Texaco for his Ferraris. Avoid Tesco and Morrisons as its cheap for a reason.... You get nothing for nothing!

To combat this we either have hardened valve seats fitted (expensive) or use an additive. There are several out there I prefer Castrol but thats just choice. There are also lead balls that drop into the tank and that is it for life. I have those but still use an additive as I want to be 100% sure.

For around 30p a tank full a shot of Castrol lead substitute beats a head rebuild any day in my book.

I agree with much of what is being said here, especially on what sort of use your engine gets. However, Carl, Ethanol was used in the Twenties and Thirties blended with petrol in a number of brands. And in the States was the first heavily used fuel up until tax hikes !

I have a Morris Minor van that had an 'unleaded' head conversion. When my son and I rebuilt the bottom of the motor last year, one or two of the seats were in a terrible state, with pitting etc. I couldn't afford to get another head, so it's still in use, I'll fix it properly later in the year. I try now to keep the revs down and not thrash her, but the gearing is low due to the van diff. If anyone comes to Kempton tomorrow, you'll see it on jumble stall 181

Previously tony_baxter wrote:

I agree with much of what is being said here, especially on what sort of use your engine gets. However, Carl, Ethanol was used in the Twenties and Thirties blended with petrol in a number of brands. And in the States was the first heavily used fuel up until tax hikes !

I have a Morris Minor van that had an 'unleaded' head conversion. When my son and I rebuilt the bottom of the motor last year, one or two of the seats were in a terrible state, with pitting etc. I couldn't afford to get another head, so it's still in use, I'll fix it properly later in the year. I try now to keep the revs down and not thrash her, but the gearing is low due to the van diff. If anyone comes to Kempton tomorrow, you'll see it on jumble stall 181

Tony, the difference between 1920's through into the 60's was that Ethanol only ever existed in a few brands and you were likely to run on E0 more than fuel containing ethanol for most of the time.

Also back then, your bile was a workhorse and wasn't laid up for weeks either by bad weather or because you had other bikes to ride and so the ethanol didn't have so much opportunity to attack rubber , carb parts and corrode your tank while also absorbing moisture.

Today almost all pump fuel (Except certain ESSO supreme synergy 97 RON) contains 5% ethanol so not a fair comparison.

Dan will be along soon with his reply from ESSO to confirm...

A couple of years ago I watched some young men from the Morris Minor club take a cylinder head apart and they were pointing out the pitting and damage they put down to ethanol.

I take your point to a degree, but I would guess that some would have had a 'favourite' brand due to cost/availability/performance that meant some may have used fuels containing ethanol on a regular basis. However, virtually all those motorcyclists and motorists of that era are no longer with us and so we can't ask them if they encountered problems. Plus of course, vehicles in daily use were subject to routine maintenance of a regularity that we would not accept or even believe nowadays. Grinding in of valves was something that everyone did as a matter of course. Perhaps now with the benefit of hindsight, we know the reason why !

I totally agree on the rubber problem, and it is such an issue even going into a motor factors and asking if the fuel hose is ethanol proof. Most of the counter staff have no idea what you're talking about. Probably safer to pay extra to get genuine oem stuff from a dealer.

I bought a length of hose a year ago from a 'jumble, guy said it was 100% ethanol proof. Within a few weeks the ends were going spongy. Bl**dy annoying !

I need to sort that head out on the Minor, but so many other projects on the go, it's finding the time. And money.