Engine conversion to unleaded

[davidmiles]

I wonder if anyone could tell me what parts need to be sent away to an engineering company, and about how much it costs to convert a standard 1098 engine to unleaded fuel. To keep costs reasonable I want to do the time consuming and far simpler servicing tasks myself. It'll be some months into the future when I'm ready to tackle the Engine, but I want to plan ahead, need an idea of approx costs. can Anyone help.
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[aupickup]

well unless you are doing a lot of motorway driving its not really worth the cost involved
just use some additive now and then

[davidmiles]

Thanks Dennis, where do you go to get the lead additive, is it freely available or a specialist item, do normal petrol stations stock up on it, or do you order it through a specialist? What form does it take, can you keep it in a jerrycan on the vehicle? sorry to sound ignorant, but Ive never seen the stuff.

[aupickup]

you can buy valve master at halfords or any morris minor place, it comes in a small plastic container and you add a cap full at every fill up, i put it in when i remeber which is not very often
i do 10000 miles ayear in my mog and never had an unleaded head in over many years of morris minor ownership

[davidmiles]

well thanks, that changes things for me quite a lot. I'll simply have to refit seals and gaskets, do the new spark plugs, filters and service bits and maybe, just maybe she will turn over. Then I can use her as she is.

[mike.perry]

You might as well knacker the head you have got before you spend money on a new one.
By the time you have paid for the parts and machining it will probably be as cheap to buy an exchange head.
The parts which need changing are the valves, guides and valve seat inserts. you can probably get away with just doing the exhaust valves. Ideally the chambers and exhaust passages should be smoothed as unleaded fuel burns hotter and this prevents the build up of carbon in the ports which can pre ignite with the hotter temperatures

This is my personal opinion and does not reflect the views of the MMOC etc etc
Just felt like saying that!

[kittyfell]

You don't need to do ANYTHING. Just run the engine, setting the exhaust valve gaps to 15 thou and check/reset them every 3000 miles. No additives required, unless doing long/hard Motor Way miles. If you really want unleaded fuel then Tetraboost is the ONLY additive that contains Tetra Ethyl Lead. The others work on sodium and or potassium mixtures and a big lump of hocus pocus. They 'may' slightly raise the octane level and so help avoid pinking, but do little for the exhaust valve seats.

[Stig]

Not all additives are 'hocus pocus', several were tested by the Federation of British Historic Vehicle Clubs and some of those were approved as providing protection against valve seat recession. They're the ones to use. It's true that only a couple of available additives raise the octane level that's not really an issue in a standard Minor engine - 91RON is fine.

But as has been said, you'll probably be fine to run without any additive if you're not doing lots of motorway driving, just check the valve clearances from time to time.

[bmcecosse]

The Fed tests were hopeless! Any 'protection' given was probably because of the raised octane. Many stories of damaged seats despite using additives that don't contain Lead. Best bet is to monitor the exhaust valve gaps and never ever let them close up.

[davidmiles]

Great advice, thanks Gents.

[Alec]

Hello all,

I don't understand some of the advice given?

"setting the exhaust valve gaps to 15 thou"

The design setting is 0.012" why set them wider, if it is to give some 'buffer' to valve seat erosion then it means either a more frequent maintenance check or use an additive which has been tested and does offset the use of unleaded petrol.

"Best bet is to monitor the exhaust valve gaps and never ever let them close up."
Fair enough to a point but how often do you need to check them?

I always use an approved additive (on a hard driven engine) and so far have not found any significant loss of valve clearance.

It does depend on the style of driving, and whether you feel the cost of an additive is worthwhile, or run the car, with frequent checks until it is worn out then fit hardened valve seats?

Alec

[bmcecosse]

Because the exhausts run hotter - they need the bigger gap to allow for valve stem expansion. Rover specified 15 thou on the later cars, even 18 thou on some! If the gaps ever close up then that's the end of the valve and/or seat. Check/reset the gaps every 3000 miles. For some - that could be once every 3 years! I too run my car 'hard' - and have had NO seat erosion with NO additives whatsoever.

[MikeHA4]

... have had NO seat erosion with NO ...

Do you say this on evidence of no change to valve clearances or on head removal and inspection of the seats and valve sealing surface?

[Alec]

Hello BMCE,

"Because the exhausts run hotter - they need the bigger gap to allow for valve stem expansion"

Fair comment but the book still says 0.012". Did later engines use different valves\materials\camshafts, which can affect the clearance required. I'm well aware that too little is worse than too much. Many cast iron production engines specify the same clearance for inlet and exhaust, including my 6 cylinder Triumph engine. The non Triumph cam I have installed specifies a 0.001" increase over standard setting for the exhaust valves.

Alec

[kittyfell]

The old books say 12 thou, but that was with leaded fuel. Later books for Metro etc specify 15 thou.
Edited to correct 'unleaded' to 'leaded'. Thanks Alec!

[Alec]

Hello Kittyfell,

I assume you meant to say leaded. The fact that later cars had a wider gap I don't dispute, but the reason why is what I was asking.
The Jaguar XK engines used to have valve clearance settings of, if my memory serves me, of 0.002" inlet and 0.004" exhaust, later engines of the same type jumped to about 0.010" and 0.012" respectively, due I think to a cam change. (I may have the figures slightly wrong but the margin was of that magnitude)

Alec

[kittyfell]

Yes of course Alec - 'leaded'. Now corrected. The unleaded fuel we have now burns hotter, so exhaust valves are hotter and expand more with risk of closing the gap. It also gives a little more safety margin to ensure the gap doesn't close up completely. That gap of 2 or 4 thou sounds like a mis-print! Corrected to 12 or 14 in later versions.

[Alec]

Hello Kittyfell,

my mistake, it was 0.004" and 0.006", and it was not a misprint, there was an engine component change that required the wider clearance on later engines. Of course the head is aluminium rather than iron.

Alec

[kittyfell]

Ahh - so then the head will expand more than the steel valve stem, and the running clearance will increase as the engine heats up. On the A series both head and valve and push-rod will of course expand, but the exhaust valve gets very much hotter than the head and rod and will expand more, closing the gap.

[Alec]

Hello Kittyfell,

yes, that's it. I don't know what the difference in temperature between unleaded and the older leaded fuel but most of that extra heat will dissipate through the valve guide so the extra 0.003" (25% increase) sounds to be erring on the side of safety. If my maths is correct then the valve would need to be an average of nearly 300 degrees C hotter to use up that extra clearance.

Alec