Morris Minor Owners Club

Is one able to convert a head to unleaded simply by replacing the valve seats with hardened ones, and still keep the original head? It seems a lot cheaper than buying a whole new "reconditioned" head to just buy the valves!

Unleaded heads have hardened valve seats and supposedly 'harder' exhaust valves. Its the valve seats that get damaged, i suppose the harder valves are just to cope with the extra heat from combustion of lower octane unleaded fuel.

yes it is possible to convert a normal head to unleaded, but it is not a diy job. could always scour ebay for an unleaded head...

Oh, all right, I got my terms confused! Valves seats and valves mixed up..
But can the valve seats be replaced? Or rather, can they be replaced by a home mechanic?
Ignore the above, just saw the preceding post. All right, I'll have a look on ebay then. Oh, and another thing; if you send a head into a specialist (ESM, Charles Ware, someone like that) will they convert it and send it back, and is that cheaper than ebay? Just wondering, being tight on money here as I already have replace most of the rest of the engine ...

As picky said no, they are machined out and new seats pressed in. Requires an engineers skill and a workshop's tools. I have an unleaded head, but on an engine. Maybe you would like to buy on an 'exchange' basis?

Exchange? What engine do you have and would you really do leaded for unleaded? Mine's a 1098...
I would be much obliged if you did!

Sorry, I forgot it's late your end... Only 6:00 here! No need to respond til tomorrow...

The cost of international shipping on such a heavy item might make it cheaper for you to find a local engineering shop who can stick a set of hardened exhaust seats in your existing head. Hardened exhaust valves are available from ESM and others.

Thanks... I'll probably do that. I'm going round to the local garage for some other stuff, may as well take the head along too when I go.

Don't bother!! Unless you are going to do many many miles - just run the car on unleaded fuel - it will be fine. If really fussy - use an 'unleaded' additive in the fuel. Worst that happens is the valve gaps close up on the exhaust side - answer - reset them ! When it eventually becomes too bad (many thousands of miles later) then is the time to either source a later unleaded head or have your head converted. It's an expensive process and just not worth it. Later Mini heads are unleaded as standard - and bolt straight on.

as mbceccose say don't bother been running mine on an unconverted head since leaded petrol went out(Same with an MGB) sometimes I put additive in but generally don't bother,Done thousands of miles in both,recently had the head off the moggie and reground the valves in, no sign of any serious burning on the exhaught seats or valves,no doubt they will need refacing someday,but certainly not yet for a long while.Just use it and forget about it untill it's a problem then look for a converted head.Why spend money when there no need to. It will not run any better with a converted head. Good luck

Same here, I did not convert my Traveller to unleaded. The only problem on the engine was a slightly burnt exhaust valve (they occasionally go on an A series anyway, lead or no lead). When i replaced it and ground the valves in I was delighted to find the valve seats were still in excellent condition. I often drive the car at 60-65mph and no harm has been done.

Just drive your car sensibly, don't thrash it and it will be fine.

Sorry didn't realise you were in the states, would be cheaper to get it machined over there, the cylinder head ways a lot and could possibly get damaged in transit.

I ran my 998 mini on unleaded and run my morris on it too - both in 1098 and 1275 flavour. Used to run old XR2 (ford Kent engine) on it too.

Might as well get some use out of your current head. If/when the valves or seats burn out then's the time to buy a new unleaded one - but until that time get some use out of your normal one.
It might surprise you and last forever.

I have burnt two valves in 5 months /6000 miles.

So I DO use a lead additive

You shouldn't have a problem finding someone over there to convert your head if necessary.
The inserts will be standard items so a machine shop will be able to install them and then grind (not cut) the correct angle for the valves which again they will probably be able to order.
One source might be MG or Mini specialists.
The local college where I was supposed to be an engineering course chucked out all their valve grinding / seat machining equipment.
Sod's law say I was too late as it was burried under several tons of other machines (I did manage to rescue loads of other useful stuff).
The tutors said no need to teach how to install unleaded seats anymore as the pupils were destined for modern vehicle where they are standard.
The machine I couldn't rescue was like a portable pillar drill what had a cutter on the end. It would be clamped to the head after centering on the existing seat / guide and then the old seat machined out.
The new seat was dipped in something like liquid nitrogen to shrink and then pressed into the recess machined in the head.
The cutter was then changed for a grinding wheel and the new valve angles made.
The valves then dropped straight in - no need to lap as traditional valves / seats.
I should add I never saw this being done and am repeating how I was told they did the job.

Paul Humphries

Overwhelming votes for not changing here- I think I'll follow the masses! And anyway, that lead additive is so cheap that it's really not worth the effort, I suppose. All right, I'll let it remain.
Incidentally, if I have to replace the valves anyway (will know in a day or two when I've cleaned them properly) is there any harm in replacing them with the "hardened" ones? I don't think the cost's any extra, so I might as well, even if I don't replace the seats. I'll always run the car cautiously anyway- at the moment the performance is average, even for a Moggy, one reason why I'm rebuilding the engine!

jackkelleher wrote: is there any harm in replacing them with the "hardened" ones? I don't think the cost's any extra, so I might as well, even if I don't replace the seats. )

I wouldn't use unleaded valves in a leaded head.
Leaded valves are lapped in with grinding paste to make a seal.
Unleaded aren't lapped in as the seat is cut to the correct angle and then the hardened valve simply fitted.
Leaded valves can have the face refinished on a machine like a small lathe with a grinding wheel on side.
Unleaded valves cann't be recut (as far as I know) and have to be replaced.
Personally I'd leave alone and use unleaded addative.

BTW LPG powered vehicles also need an addative (but few people use it)
It is applied by tapping into the engines vacuum with a simple dispenser.
I've got a new air line lubricator that I'd going to adapt to do the same job for a fraction of the price.

Paul Humphries

LPG for a car? That sounds unusual... What are the merits in a Morris?
I'll leave the valves be, by the sound of things! Don't want life being too complicated...

jackkelleher wrote:LPG for a car? That sounds unusual... What are the merits in a Morris?

Haven't you heard of running cars on LPG before ?
Over here petrol (gas to you) is very dear.
LPG is approx half the costs so is a popular way of reducing running costs.
I find my 1098 Minor so economcial, and my mileage not too high, so that it's not worth converting.
In the past I've converted several vehicles that I did high mile and the savings more than paid for the parts.
I've got a 1952 Minerva (basically steel bodied military Land Rover made in Belgium) that I intend converting shortly. At around 15mpg the consumption will restrict useage whereas I get over 40 mpg out of my Minor so that is what I clock up the miles

Paul Humphries