Best fuel for un converted 2500s

[4Hubcaps]

Hi, 

I have just taken possession of a 2500s saloon. It hasn't been converted to run on unleaded fuel and I was seeking advice on the best fuel for it 

Thanks 

 

[Sienna PI]

HI,

There's a whole load of facts and science behind this question which ranges from things like lead memory, hardened valve seats to how often and hard you will use the engine.

I am only speaking from my own experience!

I run a PI with a now high mileage engine that i acquired already rebuilt (about twenty) years ago and without knowledge of whether it had been modified for unleaded use. The engine was actually rebuilt before the phasing out of leaded petrol.

Since the phasing out of leaded petrol for the best part of fifteen years i ran it on BP unleaded 95 RON.

For about the last five years I have run it mostly on Shell Vpower 98 RON (sometimes Esso equivalent) and it has been fine.

I only used one bottle of lead additive when leaded was phased out and never bothered since!

A couple of times it has felt hessitant; On the 2016 RBRR after using fuel from the stop at Skiach which the brand of fuel i forget the name of and on the 2019 10CR using Total fuel.

Bear in mind that this is a PI though and maybe a bit more temperamental!

Maybe you could contact the person you bought it from and ask which fuel they used?

Dave.

 

 

 

 

[PeteStupps]

This is an oft-discussed topic. At one end of the scale there is the no-nonsense advice from Canley Classics: https://www.canleyclassics.com/technical-archive/unleaded-engines which just says run on unleaded and don't worry about it. 

Me, I bought a Spitfire which had done very few miles since the mid 90's. I then drove it fairly hard for 10k miles usually on 97 or 98 RON without additive and had no apparent issues - I checked valve clearances regularly and saw no evidence of valve-seat recession.

On stripping the head this winter there was some clear micro-welding damage on the exhaust valve seats, so damage was occurring. However I know it was running a touch lean for a lot of that time, which causes higher exhaust temperature and exacerbates the problem. 

Additionally a pal of mine runs a Midget as a daily driver, and found his valve clearances started closing up abruptly after a couple of years - presumably when the lead memory ran out!

So my conclusion is that valve seats definitely do get damaged by unleaded, but if you're doing low-mileage, not thrashing it, not too lean mixture, it's something I would just keep an eye on when checking valve clearances regularly and deal with if they begin to get consistently tighter. But a lot of people use additive; there's a list of ones that work here: http://www.quillertriumph.co.uk/Quiller/Unleaded/federation%20info.htm

In terms of octane, don't know what compression ratio your engine is but I would try it on standard 95 first. If you notice a gravelly rattling sound when accelerating up a hill then you might want to switch to 98 octane, or retard your ignition timing.

Pete

[RobPearce]

As Pete says, running lean is far more harmful than running on unleaded. It was the faulty carb float needle that caused my Toledo to suffer VSR on the 2008 RBRR. The GT6 has done four RBRRs since leaded fuel disappeared and shows no signs of any trouble.

If your 2500S is in standard trim then it's an unstressed, low compression engine. It will be perfectly happy on 95RON standard unleaded. Just make sure it's tuned properly.