mk1-forum.net

Ok i have just finished a restoration , The engine is VDP1100, same as MG 1100 , rebore , crank grind , original unleaded head ,I don't want to have unleaded seats fitted before someone says do that, Question is - Do i need additive ????????????????, I have asked the Question and been told yes and no , can someone point me in the right direction and if its yes what make ,type who's do i need ect, I have run Diesel cars since the early 80s , so petrol is new to me after all these years,
Thanks for your reply's
Car will only be used for occasional runs out.

Goff

If you have re-cut the valve seats in the head then you may have to use an additive. Something to do with Lead memory.
I've run my standard 998 on unleaded fuel since I bought it and done about 20.000 with it since. The tappets are getting a bit noisy now so i imagine the dreaded valve seat recession has started.

The cheapest way round this is to buy the lead caged pellets and pop them in the tank,Thats what I have done and have had no problems,I have got some if you are interested

Do a search on here, there has been a couple of good threads about it.

InimiaD wrote:If you have re-cut the valve seats in the head then you may have to use an additive. Something to do with Lead memory.
I've run my standard 998 on unleaded fuel since I bought it and done about 20.000 with it since. The tappets are getting a bit noisy now so i imagine the dreaded valve seat recession has started.

I thought with valve seat recession that the valve clearances closed up as the valve settled further into the seat ?

I've had no problems with two of my unconverted engines running on non-additive fuel. Can't say VSR won't happen though - just taking a chance and have been OK so far for normal 'classic car' usage.

Spider wrote:Do a search on here, there has been a couple of good threads about it.

Spider i tried a search and came up zero , hope somebody will find and post it up
Thanks
Goff

Here's one thread

viewtopic.php?f=3&t=10393&hilit=valvemaster

I searched "valvemaster", as this is the additive I have used in the past

If your head came off a car which had hardened valve seat inserts originally and you re-cut them, you do not need to run a lead additive.

I'm a chemist and I know a fair bit about fuels.

The whole point of lead is that it slows down the burn speed of fuel and allows you to advance the ignition, thus getting higher peak pressures and peak torque in the burn....same applies for higher compression ratios.

Off the top of my head, the lead additive consists of Tetraethyl Lead and Ethylene Dibromide (C2H2Br2). You make a sodium lead alloy from sodium metal and lead metal and then you react it with Ethyl Chloride, you get TEL and Common Salt. The EDB is an oil, you wash the salt out of it. If you put tetraethyl lead in your fuel tank, it falls to bits, the ethyl bits fall off with an odd electron which participates in the combustion process (free radicals in nerd speak) the lead is left behind as a metal. This metal kicks around in the vapour form and there is something called the lead mirror, which happens at the front of combustion....as the mixture burns and burns more complete, due to the free radicals, the lead metal vapour at the front of burning reflects heat back into the charge (probably absorbs it). The end thing meaning you get a more comprehesive and controlled burn which means you can advance the ignition and run a higher CR. We measure this as an octane number.

Anyway, if you have lead kicking around in a "burn" you get lead oxide, which is why you add ethylene dibromide. This kicks around and forms lead bromide, which does not clag up your exhaust valves.

Lots of people advertise snake oil which works. It does not. No lead pellets or magnets or phosphates or any other bits of the periodic table do the job.

If you have unleaded seats, you're probably OK. If you have a 7:1 compression ratio, you're not exactly going to blow the lead off the valve seats (lead metal lubricates it). If you use leaded fuel and then swap, the lead left behind on the valve seats is termed "lead memory". Contrary to popular belief, this burns off quicker than you'd like and is exaccerbated by lean mixes and retarded timing.

If you are running leaded fuel because you need to win at drag racing (by having the highest octane) and you are brewing your own fuel, you'd think that you'd choose 98 octane (super) rather than regular leaded. The thing is that something called "aromatic hydrocarbons" are added to the feedstock to boost octane. This is great in unleaded cars, but if you are adding aromatics to leaded fuel, they mess up the lead response. It is better to heavily lead 95 regular fuel than "super". You get an improved response on anything up to 4.5% TEL/EDB mix. If you want to go a bit further, something called "methyl aniline" added up to 1.5% also helps. This messes up your sperm and gives you cancer and is probably banned, but it does add to octane response!

You can add other things to boost octane. The whole thing being along the lines of averages. If you have a litre of X and 1mm of Y, the octane rating will be different to something with 1/2 L of both. It's like mixing hot and cold water to make a bath. I think di-cyclopentadiene has a RON of 262 or something equally silly. You then get into the world of propellants and in built oxidisers like Nitromethane and N2O.

For a bog standard grannies mini, I'd just run it on unleaded until it fails it's MOT/doesn't drive and get a metro unleaded head in the meantime.

For a racing car, I'd have a leaded head and use something called "tetraboost"

For an out and out drag racer, I'd brew something in the shed.

Goff,

For your VDP1100 intended use I would recommend using Castrol Valvemaster.

Thanks for your post In The Shed, a lot of good info there. Thanks for taking the time to post that up.

Thanks for the reply lads, especially ( in the shed ) he mentions Lead Bromide, Though i did not understand most of what was said i got the drift.
BROMIDE - I AM SURE THAT'S WHAT JANET AS BEEN PUTTING IN MY TEA THE LAST 40 + YEARS, But i just google it and they say its a myth. ,
Anyway thanks Captain for the offer of the pellets, carbon recommends Castrol Valvemaster , So i will use a additive for peace of mind.
Thanks again for your answers

regards

Goff

Must have been somewhere else the ultimate thread was written on the subject.
Briefly: the FBHVC tested all the products offered to them (for which read just the ones that worked to some extent, not the ones making wild unsubstantiated claims that were afraid to see their products face up to others...) to check valve seat recession.
Worst was Lead Replacement Petrol (used Potassium). Next Red Line (uses Sodium) - but to be fair when used in double dosage in competition engines that are unlikely to suffer sticking valves in the way a road car might it has gained a good reputation. Next Castrol (uses Phosphorus). Then Millers (uses Manganese). As oil industry chemists have always admitted, there is no "replacement" for lead in the valve seat recession context.
Lead pellets are claimed to have been successful when used in WW2 in fuel for Merlin engines in Hurricanes supplied to the Russians. It was only successful as an octane booster for the very low octane fuel available there. It did not prevent valve seat recession: it had virtually no opportunity to do so, since the aircraft operational lives were so short - thrown into combat with semi-trained Russian pilots up against Luftwaffe aces. Things weren't so great on the octane front here either. It is conveniently forgotten that the Battle of Britain was won almost entirely on imported US high octane fuel.

While its alluded to I don't think the two separate properties of lead have been emphasised enough. TEL both boosted octane AND reduced (prevented?) valve seat recession.

Alcohol and toluene will increase octane but won't do anything for seat recession. Like wise its VV for potassium and sodium compounds...

So if you're looking to "replace" lead you need both solutions... Or do what the racers do and use aero fuel - which still contains lead and so is highly illegal on the road...

Way back when lead was being removed from Oz fuel, BP did a number of technical presentations on the consequences. Apparently BP (UK) did their testing using an A Series as it was assessed as being the test bed most susceptible to valve seat recession ( From memory if they kept the test Metro below 50 mph then there wasn't that much of a problem ... at higher sustained revs the engine destroyed itself in fairly short order.

I've used stuff called Flash Lube and 98 octane unleaded in my S engine for years (decades?). While I haven't looked inside, the tappet clearances seem to show no problems with the seats. While it doesn't do anything for octane it only costs $15 to treat about 50 tankfuls. Unfortunately the label doesn't reveal anything about what's inside the bottle other than its made in Oz (although a French subsidiary is listed).

While "lead memory" is a recognised phenomena it only lasts a few thousand kays. I would not be using a non-unleaded head without taking some form of precaution....

Cheers, Ian

TetraBoost, or so it claims IS the 'leaded' bit of petrol that is missing. Anyone tried this?

www.tetraboost.com

Tetraboost is TEL and EDB in the right amounts.

That is the stuff. You need to buy a lot of it, IIRC.

This is the real real deal.