Unleaded fuel and hard valve seats

[GrahamF]

What is the current consensus regarding the fitting of hardened exhaust valve seats ?

The engine I have just bought does not show any evidence of exhaust valve recession. It has stainless (non magnetic) exhaust valves fitted.

I have never run this engine, it is in bits at the moment, and I am doing a bit of a refresh, but is it worth having the seats done, or should I not worry too much about it.

Will I keep the vehicle in the long term, who knows.

[Bumpa]

It's hard to answer the question with any degree of certainty. Popular theory says that with time the use of unleaded petrol "could" cause the valves to slowly hammer themselves into the relatively soft cast iron cylinder head. How long that time will be is not known and will depend on each engine and how it has been used during it's life. There may be such a thing as "lead memory" whereby the protection offered by the use of leaded petrol for decades continues when unleaded has to be used.

If it was my engine and it was already dismantled I would definitely get some expert like Peter Burgess to fit steel valve inserts. At the same time he could offer machine work on the combustion chambers to make the engine more efficient and powerful. Or you could just use one of the lead replacement fuel additives that are freely available. Or you could do nothing and wait for something to happen, which might take years if the mileage covered is small and the engine isn't stressed by eg. racing.

Ultimately the choice is yours. There is no "right" answer. Secondary to your question is of course the issue of ethanol in fuel, another can of worms!

[Not_Anumber]

It's worth bearing in mind that the parts that could potentially be eroded (valve seats( are the self same parts that are replaced in the unleaded conversion process.

I intend to wait if/ until any wear arises and then replace the valve seats. Given low mileages plus occasional shots of a lead replacement additive I suspect the existing valve seats will outlive me by several decades.

[GrahamF]

It's worth bearing in mind that the parts that could potentially be eroded (valve seats( are the self same parts that are replaced in the unleaded conversion process.

I intend to wait if/ until any wear arises and then replace the valve seats. Given low mileages plus occasional shots of a lead replacement additive I suspect the existing valve seats will outlive me by several decades.

You may be right. The head and valve do not seem to show any signs of erosion, but I have not stripped it yet.

The car previous owner has put some of those magic metal balls on a string in the fuel tank, so maybe I will be OK

[Vic Butler]

Those "magic balls on a string" are absolutely no good at all. They're about as useful as a chocolate fireguard and a big con trick. Get the head done properly that's the only solution.

[GrahamF]

Those "magic balls on a string" are absolutely no good at all. They're about as useful as a chocolate fireguard and a big con trick. Get the head done properly that's the only solution.

Whaaaaaaaat ? Surely not I have the brochure that came with the car, and they are guaranteed to work, AND last 100.000 miles.

I know that new seats are the only real solution, but as my piggy bank is getting a bit low, I might just use the head "as is" for now to see how it goes.

It is not a massive job to get the head off again, I had plenty of practice with A series and Triumph engines years ago.

[Vic Butler]

Ah, but would the conmerchants honour the guarantee after the valves had beaten the seat to death.
Practical Classics tested this rubbish. They had an Austin 1800 on which they reground the valves thus losing the leaded memory. Then they put the magic potion in the tank and ran on unleaded. After about 3,000 miles the head was scrap as the valve seats had recessed beyond repair. I can't remember whether they tried to claim on the warranty but if they did I suspect they didn't have any luck.

[GrahamF]

Stripped the head today, and it turns out that the reason there is no exhaust valve wear, is because it is already fitted with non magnetic valve seats and valves ! No idea how long they have been fitted, but the seats are really good !

Makes a change to have something go my way !

[Not_Anumber]

Thats a happy discovery.