Petrol Additive

Hi,
Recently bought a 2.25 petrol SIII, when I asked the guy I bought it from about using unleaded he said he added an STP " complete Fuel System Cleaner" for petrol engines. He told me to add 250mls to the tank after every 3 or 4 fills. The instructions on the bottle says to add 500ml to a full tank every 4000 miles. Does anyone have an opinion on this or a suggestion for using unleaded / engine cleaners?

Hello mate I use the Castrol leadmaster lead replacement additive in my series its a little expensive but it does the job. Are you using just the cleaner or a proper lead replacement? I think that eventually you will need to get the seats done. My valve clearance's are always closing up.
Good Luck

Thanks for info, I think the stuff I use is for cleaning general petrol engines, is the gear you're using still causing fouling? But it sounds a bit better than what I'm using, do you add it with each fill?

snake oil.
just use a bit of redex or similar for every full tank if you really must.

thanks ormus, but can you give me a bit more detail - how much redex should I add to say 50 lts of petrol?

i think it sez on the bottle

Fair enough Mad Hat - but I'd expect it to say that for regular engines ie every 500ml to 50 lts every 4000 miles etc but for regular use I'm not sure, the STP cleaner product I've used says not to over use the product ( ie after every 4000 miles ) - I'm sure Redex is the same unless its a specfic unleaded additive.

In my mini which runs on leaded petrol i use castrol valvemaster, there are to reasons for the additive, one it raises the octane rating to stop pre igniton and two it adds a lead type substance to coat the valves, as unleaded doesnt protect valves as lead acts as a lubricant, by using an engine cleaner you are striping away the lead memory which will lead to the valves been burned away. you can either use some lead additive such as castrol valve master or get the exhuast valves and seats changed.
Cheers
JD

Does the lack of lead replacement cause 'pinking'? Mine seems to do this alot under load and thats all i can think of?

Thanks soul-racer, that's exactly what I needed to know!

ians3 said:

Does the lack of lead replacement cause 'pinking'? Mine seems to do this alot under load and thats all i can think of?

Click to expand...

that ill be wrong ign timing or too low a octane fuel most probably

Pinking is caused by pre ignition which is either the timings a few degrees out or the octane rating of the petrol is wrong, the lead additives tend to contain an octane booster as unleaded has a lower octane rating than leaded, so if ur engines been converted ur timings wrong, if it hasnt the lead addivite should stop it unless there is somthing else wrong.
Cheers
JD

is thur a echo in here??

sorry mate didnt see yours when i posted mine.
Cheers
JD

Cheers for the info chaps.

How do i know if its been converted or not? (i assume it must have been!!). Its a 5 bearing engine with the lime green paint.

I will start by adding more lead replacement as i only do this now and again and not every fill

Ian

Having trawled for info on Castrol Valvemaster, I see the triumph users club recommend its use after having conducted trials on it, they also had some price lists for unleaded conversions which didn't make for nice reading - by the way how does "pinking" manifest itself?

its pre-ignition. in that yer fuel/air mix is ignited by another source before the sparkplug sparks. and the noise is the sound of the pressure waves bouncing around the combustion chamber

thats the simple version..

feck it, diesels sound so more simple!

phoenix said:

Hi,
Recently bought a 2.25 petrol SIII, when I asked the guy I bought it from about using unleaded he said he added an STP " complete Fuel System Cleaner" for petrol engines. He told me to add 250mls to the tank after every 3 or 4 fills. The instructions on the bottle says to add 500ml to a full tank every 4000 miles. Does anyone have an opinion on this or a suggestion for using unleaded / engine cleaners?

Click to expand...

I chuck one in now and again... every few months.. mines is a '75 so the way i look at it is that it had years and years of runnin on four star thus lining the seats wiv lead... a little top up now an again doesnt hurt but not evry fill....

Dont use anything like the fuel system cleaner as it will strip the lead coating away quicker, use some lead additive every 3/4 by all means it will prolong the lead coating though it will still wear away eventually, and most lead additive also changes the octane rating.
Cheers
JD