Hardened Valve Seats

[gmunro]

I have had conflicting advice regarding upgrading my 1967 Series 1 4.2 E-Type to running on unleaded fuel. One opinion is that the 4.2 E-Type always had hardened valve seats and therefore new seats do not need to be fitted. The other opinion is the absolute opposite - new hardened seats must be fitted. I would be very grateful for further comments on this. Much appreciated.

[Alty Ian]

All XK engines have them. Whoever is advising you that they must be fitted knows nothing,... or wants you to pay them some money

[mgcjag]

Totally agree with Ian.......whoever your talking to dosent know there stuff....the heads are alloy so hardened seats were fitted.....just use the highest octane unleaded you can get...it will run better..although you will probably be ok with regular if you cant find premium and you need fuel...

[PeterCrespin]

I have had conflicting advice regarding upgrading my 1967 Series 1 4.2 E-Type to running on unleaded fuel. One opinion is that the 4.2 E-Type always had hardened valve seats and therefore new seats do not need to be fitted. The other opinion is the absolute opposite - new hardened seats must be fitted. I would be very grateful for further comments on this. Much appreciated.

It's all relative.

The XK used chilled iron seats, which are harder than the material used in cast iron engines that have the seats cut into the head. To that extent, the use of unleaded is acceptable without modification and your 'must fit' advisor is wrong.

However, chilled iron is far softer than truly hard modern valve seats like stellite and similar alloys, which generally last the life of modern engines with no maintenance or valve adjustment. This may be overkill for a hobby engine but if I were ever needing to fit new seats to an XK it's what I would ask for, especially on the exhaust side.

[tinworm]

Quality cylinder heads of Par Cornwall fitted my 3.8 head with modern seats as well as a load of welding plus a skim and pressure/leak test - ?500 .

Barrie

[christopher storey]

The original seats are perfectly adequate unless damaged or cut back so far that the valve(s) have become pocketed. It is highly desirable to retain the originals where possible because there are instances where replacement seats have dropped out of the head with predictable consequences

[gmunro]

Many thanks to all who replied. I have my answer! The forum is a brilliant resource - thanks once again.

[nbanks44]

Also agreed.
I have about 100k miles on the 66 mk10, (same head as your e-type), since the last valve job which at the time was nothing more than installing new guides, (phosphor bronze), and lapping with grinding paste by hand.
At that time, about 20 years ago the car had about 50k on it.
So, yes all in about 150k on the car and of course the original valve seats and no smoke and still good compression and the last twenty or so years on unleaded but high octane fuel and never any additives.

[gmunro]

Thanks for your response nbanks44. Your input much appreciated.

[Bernie2015]

Do you know if this advice also applies to a 1969 series 2 4.2 engine?

[chrisfell]

My '67 E-Type has run on unleaded ( 95 97 98 and 99 octane ) since 2003, covering almost 50,000 miles. If XK engines needed hardened valve seats, mine would have had problems before now. No additives have ever been put into the fuel.

Best advice anyone can receive when told an engine in their E-Type needs hardened valve seats is to find another expert to look after the car. The current one doesn't know his onions.

[mgcjag]

As Chris said above and all the others to....mine is a S2 69 2+2 it needs no conversion for unleaded....it does run best on the highest octain you can get...premium fuel

[christopher storey]

Yes, it applies to ALL XK engines from 1948-1992 !

[malcolm]

Yes, it does. I have a 1969 series 2 4.2, with original seats etc and it's fine on unleaded.

[38E]

Another thing is that valve seats on XK engines are not something you want to change or mess with unless it's absolutely necessary such as when the seats are too low to obtain proper valve clearance.

I considered it once until I asked the various machine shops how they would change them. None of them were going to use the proper procedure described in the manual, in fact some of the methods described were horrific. So I fixed it another way.

Changing thee seats for unleaded gas is totally unnecessary anyway.