Morris Minor Owners Club

If you lap in the valves on a head does it remove the lead memory?

Thats a good question and I would assume some of it would be removed but I dont know if there is a way of measuring the lead memory anyway, as normally most would just have an unleaded conversion done anyway lets hope somebody knows the right answer.

leyther8008 wrote:If you lap in the valves on a head does it remove the lead memory?

Depends how long it ran with leaded fuel, and the amount of metal removed while lapping.

Hello 8008,

yes, I would say that you will. to get a good seal you will be back to the cast iron of the head. You can run it again on leaded to rebuild the memory if you want?

Alec

Bare in mind leaded fuel is £1.80 a litre if you can find a garage that still sells it. Only one additive has the Tetra Ethyl Lead ingredient (Tetraboost.) In any case unless you lug the engine, valve recession shouldn't be a problem with modern unleaded fuel. You will know if it's happening, as the exhaust valve clearances will start to close up (reduced tappet clearance).

Hmm just thought I,d ask as I havnt really got the spare for an unleaded head at the moment I was only going to lap them in as a general clean up of the head, but if its only microns thick (the lead memory) I think I will leave it and save up my conkers.
Thanks to all for taking the trouble to reply.

If you use the car regularly It would be worth using an additive . it wasnt a minor but I used to use castrol valvemaster in another car I had with soft seats . I drove it daily & did a few trackdays no problems with valve recession.
also unleaded fuel is how I came to own my minor as the previous owner drove it untill it stoped.

If it aint busted, don't fix it

Forgive my ignorance- what is lead memory?

The hardness of the area surrounding the valves that the lead in leaded petrol builds up, which remains for some time when you start running on unleaded petrol
a

I see! Thank you.

I have often wondered whether rubbing a piece of lead over the clean surfaces of the valves and the valve seats after they have been ground in would in any way restore the 'lead memory'.

Seems just a tad unlikely, doesn't it ;)
a

Why do you think it is unlikely to work?

Because it would have no effect whatsoever. The leads got into the head by the pressure and heat of the combustion process, and rubbing a bit of lead on would be as effective as alchemy.
I'm not a scientist, btw, so that's just my take on it

Inclinded to agree with you there Andrew