Unleaded fuel.

Dear PapaJack, welcome to the forum!

If you ask 10 TR enthusiasts about leaded vs unleaded your likely to get 10 different answers. 

Here are some comments from a few long time TR people.  The original question is under-lined and the responses are in bold.

Regards,  Tags

Hi all. I was looking through a 1975 TR6 handbook and read this about the TR6 engine (U.S.A.) and I quote, "The engine is not designed to use unleaded fuel, and whilst the occasional tankful will not cause damage, constant use of unleaded fuels will result in excessive wear which will affect the emission control system." The handbook also states that the TR6, (U.S.A.) performs efficiently on fuels of 91 octane (regular fuel). Who of you out there is putting "High Test" gas in their TR's. In my neck of the woods the medium octane level gas is 87 octane. I assume that level of octane (87) would be high enough for the engine to operate efficiently. What's your take on that?

This seems a bit odd to me considering that unleaded fuel is practically the only kind being sold now and has been for a very long time now. I can't even remember when is was that I last saw regular fuel for sale.

What do you think about this? I'm assuming that all of you are using unleaded fuel in your TR's. Am I correct in assuming this? Please tell me if I'm not.

Thanks in advance for your input.

-------------------------------------------------------------------------------------------------------------------------------

As for leaded vs. unleaded, all the master mechanics I know don't use lead substitute in their own cars (including hi-po Chevys, Cadillacs and Oldsmobiles.) I don't use substitute in my cars, because I basically put so little miles on them each year that I don't worry about any damage.

_________________________
Sam B.
Automotive Journalist,
--------------------------------------------------------------------------------------------------------------------------------

Actually I don't find it surprising a 1975 owner's manual would talk about both leaded and unleaded fuel. Both were available at the time, with unleaded being phased in and leaded being gradually phased out.

And, if you are going to drive the car today, you won't have much choice, it will have to be on unleaded fuel.

In a nutshell, lead was added to increase the octane of fuel. Higher octane burns cooler. And, lead provided lubrication to the valve mechanisms: guides, valve faces and stems, and valve seats.

There was a lot of concern in the U.S., and elsewhere in the world, about the transition to unleaded and it's effect on the cars. It's well documented that valve guides, valves and valve seats can wear a lot faster without lead in the fuel. That's particularly true of the exhaust valves, where higher temps are more common. Thus, valve seat recession occurs. That's where the seat under the valve, machined into the head, gradually erodes. The valve slowly gets out of adjustment, is one clue that this is happening.

A car driven hard will see valve recession and guide wear faster than one treated more gently, because the "spirited" driver's engine is working harder and running hotter.

Without getting into metallurgy (not that I know much about it anyway), it so happens that certain cast iron formulas have some natural resistance to valve recession. And, it so happens, the 4-cylinder TR's head was made with this sort of material. So, these particular engines are not prone to that sort of unleaded-fuel-related problem, if driven gently. Unfortunately, I can't say if this is true of any of the other Triumph cylinder heads, 4-, 6- or 8-cyl. Just the TR2/3/4.

Even though they wear slower than most, if apart for a rebuilt, it would probably be prudent to have any Triumph cylinder head, or any other pre-unleaded motor for that matter, exhaust valve seats worked over for unleaded use. This involves either having the existing material treated and hardened, or installing a hardened and treated insert.

Typically, upgraded valves are needed too, specially materials for use with unleaded fuel, especially the exhaust valves.

Valve guides are another story in the 4-cylinder TRactor motor, and I'm pretty certain in all the Triumph models or virtually any pre-unleaded cylinder head. As soon as practical, they should be replaced with a special bronze type that have self-lubricating properties.

Finally, some de-tuning of the engine may be needed to cope with the fact that unleaded fuel is lower octane. The ignition timing might need to be retarded more than originally. Also, engine compression might need to be lowered in some extreme examples (not very likely in an unmodified Triumph).

To give you some idea the difference fuel octane can make, just the other evening I was watching a TV show about Doolittle's air raid on Japan in 1942. They flew B25 bombers off aircraft carriers, something no one thought was possible. These airplanes typically used 200 + ft. of runway. Now they were training to be able to get airborne with under 500 ft., even 450 ft., with a load of 500lb bombs and a double load of fuel on board. In a reenactment test, the best a modern pilot could do in an *unladen* B25 was 900-1000 ft (with 2000 ft + being more typical). There were several factors, but one of the top ones he cited was that 130 octane fuel was used in 1942, while only 100 octane airplane fuel is available now.

Today's unleaded is lower octane, so, yes, I will use only premium in my TR4.

There are some "lead replacement" additives you can buy, that help a little. But, not much.. These can be found at most auto parts stores, merely are intended to help cars that haven't been converted for unleaded fuel "get by" on it for a while. Some of these both boost octane and add some lubrication properties, but most just help with the latter. _________________________
Alan Myers
San Jose, CA
'62 TR4 CT17602L

I wrote the following based on much research and my own experimentation. http://triumphregister.lefora.com/2009/12/30/lead-octane-booster/
I swear by this stuff and as I mentioned in the bit I wrote, I use in in my 1963 TR4 and my 1976 KZ900 motorcycle. It's expensive buy I feel that with the protection against valve recession and wear and the added performance increase, it's worth it. Check it out. Good luck! d

Tags: as always, nice thoughtful and thorough response. And in reading through this bit, which happens to be of great technical interest to me, it seems that there is much out there about the negative affects of unleaded fuels. (The positive comes off to me as merely speculation, but that's me.) The abscence of lead "may" cause damage, or, ...unleaded "can" promote valve seat wear, low octane, pinging, de-tune, ...holy mackrel! There's too much advise on how to "live" with the aweful effects of todays gas, and I wonder, who would want to de-tune anyway? Some say to replace the seats and valves with more modern day materials "as soon as practical". Others are saying they have been running unleaded for years with no problems (yet). Everything is always fine until that ugly day arrives when you begin to hear those valves clanging and experience poor performance. Why gamble? Seems to me that all this points to one conclusion. These motors are better off with lead. So I run lead and not a substitute. In the end, if it matters not, then I will have spent more than I should have. But if it does matter, my Sons childrens childeren will be wondering who we were who kept these roadsters alive for generatiuons to come.