Lead Free Petrol

On or around Mon, 12 Dec 2005 14:04:01 +0200, Bob enlightened us thusly:

You might want to retard the timing a few degrees (about 3, ISTR, from a 98 octane setting) depending on what octane rating they give you. Ours is 95 octane, whereas leaded 4* used to be 98.

as to the lead... you might be OK with an '85 engine. I think it's only early ones that are prone to damage, and not all of them - being an alloy head, it already has valve seat inserts. The biggest problem engines are cast-iron heads with the valve seat machined straight into the iron.

Didnt we loose leaded petrol in the uk in about 98? I'm not sure i've ever bought any for my own car?

Are there many 'modern' (meaning 70's onward) cars with cast iron heads?

All my cars have been old (84 is my newest), and I was always of the opinion that i'd just stick unleaded in my cars and if i ever had any head trouble i'd sort it out when it became obvious. None in any of them yet! (and i've had plenty of heads off to check!)

Around that time.

Crikey, where do we start here! Nearly all BL cars of the 80's (apart from the O series i think) had CI heads. My old R5 Gt turbo had a CI head.

TBH, loads of cars & all dervs that I know of have CI heads.

I will, of course, be wrong now.

Nige

-- Subaru WRX Range Rover LSE (Bob)

'"gimme the f*ckin' money"

The BMC A-Series used in Minis, Allegros and Metros up until 1998 had cast iron heads.

The B-Series used in the Maestro and Montego had cast iron heads.

The lump Vauxhall put in the Chevette and Nova had a cast iron head.

And that's just off the top of my (cast iron) head.

Yes - there are many modern cars with cast iron heads.

P.

Well it wasn't the lead free petrol my last engine died from. With an old engine you might as well not bother with any fancy conversion because whats the point of spending a lot of money on something that is not going to last anyway.

On or around Mon, 12 Dec 2005 23:21:55 +0000, "Paul S. Brown" enlightened us thusly:

Ford kent (pushrod), the littel one in the fiestas (valencia?), ford pinto, ford cologne V6...

and of course the 2¼ and 2.5 land rovers.

leaded petrol was phased out and repalced with LRP which has in turn disappeared. buggrem. They said "don;t worry, all you types with old motors, we'll do LRP instead." And so they did, for about 3 years.

On or around Tue, 13 Dec 2005 00:34:43 -0000, "Larry" enlightened us thusly:

and if you're doing a major rebuild on an old engine, then you get the head converted at the same time.

I must have got far too used to saabs (which definately have alloy heads!)

Thanks for the info.

We are getting a Lead replacement petrol. Guess I will use that out of choice but nice to know no harm will come from using unleaded. The Octane rating stays the same since we are at altitude. I think 93 and at the coast they will get 95.

As an aside, I still run a 1983 Mk1 Fiesta XR2 (Kent OHV CI head, owned from new) and started to note pre-ignition problems whilst running on 4 star in the early nineties.

ISTR that the lead levels were being slowly reduced, and with them the octane/cetane figures were also being altered.

To run on standard unleaded was a no-no as basically it was the equivalent to putting 2 Star (ish) into the engine, with the subsequent required retardation in ignition settings meant that the exhaust valves were opening when the fuel charge was still burning.

This led to very high exhaust temperatures ( discolouration of the exhaust manifold) and would eventually lead to valve seat recession.

From 1995 onwards I have only used super-plus unleaded which has a higher octane rating than the old 4 star, so no ignition retardation is required, and the engine never suffers from pre-ignition, nor has there appeared to have been any valve seat recession as valve clearances don't seem to need any more attention than previously normal.

Most of the V8 engines were designed to run on 'regular' petrol in the states (87 Octane) with the exceptions in this country being the Rover

3500 Coupe which had 100 octane (5 Star heads) and some of the Police P6's including variants like TR8, MGB GTV8 etc (4 Star mainly due to cam changes).

A low comp. 3.5l should not need ignition retardation, but coke build up on the piston crowns may bring the compression high enough to require a 1 or 2 degree alteration, its really a case of try it and see.

My Disco has the High compression 3.9ltr which is still quite happy to run on standard unleaded as detailed in the manual.

Hope this helps

Lofty

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