Lead memory in heads

Post by **leyther8008** » Tue Mar 11, 2008 3:30 pm

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

Post by **Kevin** » Tue Mar 11, 2008 4:33 pm

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.

Post by **MoggyTech** » Tue Mar 11, 2008 6:14 pm

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.

Post by **Alec** » Tue Mar 11, 2008 6:41 pm

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

Post by **MoggyTech** » Tue Mar 11, 2008 7:04 pm

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).

Post by **leyther8008** » Tue Mar 11, 2008 7:38 pm

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.

Post by **Mogwai** » Tue Mar 11, 2008 7:39 pm

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.

Post by **MoggyTech** » Tue Mar 11, 2008 7:40 pm

If it aint busted, don't fix it

Post by **jackkelleher** » Thu Mar 13, 2008 6:03 pm

Forgive my ignorance- what is lead memory?

Post by **bigginger** » Thu Mar 13, 2008 6:18 pm

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
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Post by **jackkelleher** » Fri Mar 14, 2008 2:24 am

I see! Thank you.

Post by **newagetraveller** » Fri Mar 14, 2008 7:38 pm

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'.

Post by **bigginger** » Fri Mar 14, 2008 7:53 pm

Seems just a tad unlikely, doesn't it ;)
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Post by **newagetraveller** » Fri Mar 14, 2008 8:01 pm

Why do you think it is unlikely to work?

Post by **bigginger** » Fri Mar 14, 2008 8:18 pm

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

Post by **Kevin** » Mon Mar 17, 2008 12:37 pm

Inclinded to agree with you there Andrew

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Lead memory in heads

Lead memory in heads

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