Lead Replacement

[Majicmark]

Can anyone tell me if in line units work as a lead replacement. I have been given a Fuel Saver unit which i was told could be used instead of Additives. I am a little sceptical of any of these things as you hear contradicting info. Has anyone used one successfully or am i better sticking to the Additives.I intend to take my P6 2200 on a long run & want to be sure i am protected as best i can be.

[JPB]

Your P6 needs no additive. If it did, them this type of thing is a complete waste of money. If it pinks then use 97 or 99 RON fuel instead of premium 95.

[Majicmark]

I didn't realise the P6 was ok without additive. The engine runs sweet since i re-shimmed tappets last year with no pinking or running on. Thanks for the info & also confirming my thoughts about gismos.

[SirTainleyBarking]

What JPB Said. These in line or drop in tank lead replacement devices are, to put it in a manner that won't get me sued, of non proven benefit.
They have been tested in lab conditions (On an A series engine, something that will recess valve seats given half a chance) and found to perform in exactly the same way as straight unleaded fuel.

So save your money for fuel (Super unleaded if it pinks) as you'll need it

I do use the Castrol Valvemaster product on my 6 cylinder Landrover. Mainly because this engine is known to be weak on the exhaust valves, and as they're in the block its a right royal PITA to swap them out

[Willy Eckerslyke]

Your P6 needs no additive.

In case any other P6 owner is reading this, can we clarify that you're saying this as it's a 2200 and not suggesting that all P6 models are OK on unleaded?
(Personally I'm quite convinced that the 2000 engine needs an additive.)

[karlsgazelle]

That's very interesting.
Can anyone tell me about my Rootes 1725cc engine (1966/7ish, cast iron head)? Does it need lead replacement additives?
I've been using the stuff since I got the car, but it always runs perfectly, no pinking etc., I'm now wondering if it is necessary at all.

Thanks
Karl

[TerryG]

The V8 would be OK on unleaded (unless i have been misinformed) because it is an ally engine so has "hardned valve seates" pressed in as standard. I can't speak for the smaller engines though.

[JPB]

OK, with a cast iron head, other than those fitted to late (post-1988) A+-series and similarly late, iron-headed stuff then it's best to use a lead substitute with any iron head since chances are that it won't have been machined to take steel inserts, unless you know that it has of course.
But with any aluminium head that has pressed-in seat inserts, the material used for the seats must by default be hard enough to take the unleaded fuel and equally must have exhaust valves of a material that works with that harder material. Any softer materials, such as cast iron, won't be close enough in coefficient of expansion to remain intact when an alloy head heats up.
The harder Steel used in aluminium/aluminium alloy heads for valve seats has a compatible coefficient of expansion, so the seats won't be in any great danger of dropping out. By happy coincidence, that harder material is by its nature suitable for unleaded fuel.

I am aware that there is a school of thought which considers the valve seats in 2000s insufficiently hard for use without lead or its substitute however an engine builder locally who has done a great deal of work for me both professionally and for cars of mine over the years informs me that the tube stock from which he makes seat inserts is exactly the same grade of steel as that found in all P6 valve seat inserts and that the only difference with the 2000 (and earlier V8s) isn't a metallurgical one at all but simply an issue of those engines requiring 5-star fuel originally, where the 2200 was happy on lower octane fuel, so better suited to the lower octane - 3 star equivalent - Premium unleaded now.

But from the purely metallurgical point of view; the seat material used in any ali head must be hard enough for fuel without lead if it's of a grade that has a coefficient of expansion that allows it to stay put in aluminium. So earlier aluminium/aluminium alloy-headed engines won't suffer seat recession as a result of using fuel without lead, but may, in some cases, require super unleaded or an octane boosting additive in areas where super isn't available at the pumps. They still don't need the lead however.

This applies to more British engines than some may have thought:
Alloy-headed versions of Rootes' 1725cc OHV engine, all Triumph Dolomite/Saab 99 OHC engines, the V8 in the Stag (in spite of some "specialists" charging owners for "unleaded conversions"), O-series, all OHV Reliant engines in 600, 700, 750 and 850cc forms, Imp & 928cc Sunbeam engines, Jaguar XK engines and doubtless others that I haven't thought of at this time.

So, if you have an engine with an aluminium alloy head that was designed to run on 5-star, use super unleaded or an octane booster since retarding the ignition timing alone won't be an ideal solution in those few cases. If, however, you run one of the engines designed to be able to use 3 star or below, then fill up with 95RON "premium" unleaded and only use super if it pinks and that pinking can't be addressed by retarding the timing by a very slight amount.

When I owned my first Dolomite, back in the mid '80s to the early '90s, unleaded fuel was still comparatively new but I used the stuff in that engine from shortly after purchase at 35,000 miles right through to when the head next came off - when the guy I'd sold the car to paid me to overhaul the engine for him - at 215,000 miles. That had suffered no seat recession, no pocketing, no signs of trouble at all in fact and the valves were all seating every bit as well as they'd done when the engine had covered only 35k. After checking all of the valves, it was found that they could all be replaced with the same shims that I'd used to set their clearances all of those miles and years earlier. Mentioning this finding to a colleague at the time was what led me to expose the number of "conversions" for which Reliant owners had been charged but didn't need and it's been a bit of a pet subject of mine since.

Sorry to have gone on at such length, cheers,

[karlsgazelle]

Superb information as usual on here, thank you John and Terry.

[Majicmark]

That is very interesting i am in the trade myself(moderns mostly) but did not ever have cause to consider the alloy head & seats issue. Makes sense when you think about it but useful to know for the future. Many thanks for all input especially John & Terry seems to be creating some interest too.