Hardened Valve Seats

[martinstag]

In the current issue of Practical Classics magazine one of their experts asserts that almost no-one with an alloy-headed engine need worry as almost all cars with aluminium heads have hardened valve seats. Can anyone on this forum confirm that the aluminium heads on a Stag were fitted with hardened valve seats as standard.

[PeteJS]

As far as I understand the valve seats are indeed a hardened steel insert. The only upgrade that could / should? be undertaken is to fit TR7 exhaust valves as these are better suited to unleaded petrol.

[Guest]

one of their experts asserts

What sort of expert is that?

Does he make or design valves for competition engines?
Does he work on engines?
Does he have a rockwell or vickers hardness tester?
Does he work for Federal Mogul?

[jagorstag]

What sort of expert is that?

Does he make or design valves for competition engines?
Does he work on engines?
Does he have a rockwell or vickers hardness tester?
Does he work for Federal Mogul?

All very valid questions Gareth, and I suspect the answer is mostly in the negative, unless that 'expert' has confirmed it with an actual expert...

What would your take be on this?

Cheers,
Joakim

[LD334]

Check out the comment from Jim Parkinson quoted on p65 of 272 below. His expertise is that he was responsible for the design of the Stag engine.

http://www.stag.org.uk/technical/index.htm

[Ritchie6]

When I first got my Stag last year I made a few enquiries and I seem to recall reading somewhere that it was designed with the American market very much in mind and that meant it was suitable for unleaded. I did wonder about any benefits of occasionally topping up with a higher octane fuel which is available at some petrol stations but haven't come to any conclusions except that it's about 10p a litre dearer but may have little or no effect on the engine

Richard

[mole42]

All too easy to become a magazine expert.
Good call from LD334 to an actual expert!
I’ve tried the higher octane fuel occasionally but noted no advantage.

[Guest]

I seem to recall reading somewhere that it was designed with the American market very much in mind and that meant it was suitable for unleaded.

"Unleaded valves" are mostly a widely used industry con.
Hardly any of them are.

So were the "supposed unleaded" Spitfire california spec 1500 heads with so called "hardened" seats.
Those cars were fitted with catalytic convertors and a single Cd type carb.
I think some of the valves I remember were actually stellited but the seat material was rubbish*.

They had so much torque they sent them Birds custard powder as an optional extra to see if the car could be hitched up, & see if it could pull the skin off.

I had a bunch of those heads.
They were terrible rubbish that fell apart with the things having almost no compression after a few 1000s of miles.*

Anything "designed" by any factory to work on unleaded fuels under the dreaded BL period should be taken with a big pinch of salt.
Almost NONE of the Triumph valves were ever stellited, they were always 2 piece friction welded items.

Jaguar valves, by contrast have been of high quality as have the seats since the 1950s.
As far as I remember, most of them stellited especially the V12s and the 6 cylinder engines that followed them.
There were often bad things said between the 2 companies in Coventry.

The ability to run on unleaded without damage mostly comes from compatibility of metals between the 2 seats.
Most Triumph exhaust valves are pretty soft. So are the seats.
The only reason why STAG don't wear so badly, or the seats knock out is the much lower seat pressures compared with the pushrod engines and the unbelievably low combustion pressures and low state of tune.

I believe it's why Faversham change the seats routinely and put modern ones in....

FYI,-
My 1980s Coventry made engine is designed to run on unleaded & has stellited valves from the factory, but they still aren't very good....
not like say a 1980s HONDA V6 engine IS GOOD, and can do 300 000 miles and still not use any oil....

[DJT]

Check out the comment from Jim Parkinson quoted on p65 of 272 below. His expertise is that he was responsible for the design of the Stag engine.
http://www.stag.org.uk/technical/index.htm

It’s a pity many so-called Stag experts don’t take note of that, including firms that charge owners for ‘unleaded conversions’.

The thing to to be aware of is the exhaust valves. OE exhaust valves have the part number 155524VL stamped into the stem. These will happily take unleaded 95 octane petrol. Some aftermarket exhaust valves supplied in the 90’s were of poor quality and burnt out in a short time (<25,000 miles in the case of a replacement head from a famous supplier in Lincolnshire bought in 1992. The seats were fine). Original or reputable replacement exhaust valves supplied nowadays should be fine.

[richardthestag]

In the current issue of Practical Classics magazine one of their experts asserts that almost no-one with an alloy-headed engine need worry as almost all cars with aluminium heads have hardened valve seats. Can anyone on this forum confirm that the aluminium heads on a Stag were fitted with hardened valve seats as standard.

my understanding but not expert knowledge (I have no credentials nor professional accreditation)

Stag heads exhaust valve seats are up to the job, there was a suggestion that the original exhaust valves fitted to early engines were prone to receding into the good seat.

Has anyone witnessed this?

TR7 exhaust valves seem ok, certainly are on my engine*
(although it has only done 30k ish miles under my ownership I am not shy with the throttle, do not use any additives, do check valve clearances periodically and have once adjusted to accommodate wear in the bucket surface on one inlet)

Anyone know if original "Not good for unleaded" exhaust valves are even available still or when they went out of production?

[richardthestag]

What sort of expert is that?

Does he make or design valves for competition engines?
Does he work on engines?
Does he have a rockwell or vickers hardness tester?
Does he work for Federal Mogul?

phone them up and ask?

[tonyh]

Below is a copy of a post from me back in February 2015, should answer your question.


When unleaded fuel was first introduced I did a lot of research into what was needed for the Stag to run on unleaded fuel, I spoke to BL technical department and they told me that the exhaust valve seats were already good for unleaded fuel but the exhaust valves were not, BL knew the Stag had to be ready for unleaded fuel for the US market but to save money the bean counters at BL said use standard valves for the UK and European cars.
The next step was to see if the information from BL was correct. I had a good customer that used his Stag as everyday transport and covered a reasonable mileage of mixed town and motorway driving who was willing for us to carry out the tests. The heads were removed and rebuilt, some cylinders had original exhaust seats and exhaust valves, some had unleaded exhaust seats fitted with standard exhaust valves, some had unleaded exhaust seats fitted with unleaded exhaust valves and some had original seats and unleaded exhaust valves. Every 2,000 mile we measured the valve clearance to check for valve recession, the clearances remained the same throughout the test, after approximately 9,000 miles the heads were removed, striped and checked. The original valve seat with unleaded valves were good, unleaded valve seats with standard valves showed very slight pitting on the valve face but none on the seat, unleaded valve seat and unleaded valves were good, original valve seat and original valves showed very slight pitting on valve face but not the seat.

So to summarize, all you need to run on unleaded is new valves. Standard valves have not been available since the early 80’s all exhaust valves, not only Stag exhaust valves, have been made to unleaded spec, if your heads have been rebuilt in the last twenty years or so you will have unleaded valves already.

The Stag will run fine on regular unleaded fuel, if you experience pinking check the ignition timing, it’s very unusual to retard the ignition timing to stop pinking due to regular unleaded fuel.

In the mid 80’s one of the classic car magazines ran a series of tests with the unleaded additives that were available and found none of them worked properly, if I remember correctly the test were carried out on the BMC A series engine. The only additive I would use is Redex.

Tony.

[SteveD]

Tony, that's a really helpful reply, thanks. I'll just use Redex in future.

[Mark Serj]

What kind of benefit does Redex give in Stag terms please chaps?

[Guest]

Below is a copy of a post from me back in February 2015, should answer your question.

I had a good customer that used his Stag as everyday transport and covered a reasonable mileage of mixed town and motorway driving who was willing for us to carry out the tests.
The heads were removed and rebuilt, some cylinders had original exhaust seats and exhaust valves, some had unleaded exhaust seats fitted with standard exhaust valves, some had unleaded exhaust seats fitted with unleaded exhaust valves and some had original seats and unleaded exhaust valves.
Every 2,000 mile we measured the valve clearance to check for valve recession, the clearances remained the same throughout the test, after approximately 9,000 miles the heads were removed, striped and checked.

You sure like getting your hands dirty Tony.

Most people have no idea just how many hours of labour is involved in all that.
That represents a lot of work and time, and most of it just goes into the "experience" drawer...

I know just how thankless a task is involved in doing long term stuff like that.

Even more thankless was the fact one of the UK's best valve manufacturers was just down the road from Jag and Triumph in Coventry on Torrington avenue.
This was brainlessly vandalised by the efforts of Cov city council, who kept putting up the industrial rates in that area until they become truly unsustainable..

I can't remember the name of the company in question any more, but he warned them repeatedly if they kept doing so, he would be obliged to close the business down.
A sort of arm wrestling match ensued, where they simply wouldn't believe him "issuing idle threats or the like".
So, close he did, meaning the UK has only a few high quality manufacturers left.

Just ONE for gudgeon pins in Weymouth

Just ONE for engine valves (who supplied Cosworth for years for their famous DFV).

Just ONE for camshafts in Lydney (part of federal Mogul now).

NO liner manufacturers any good, NO piston ring manufacturers any good, and NO cast iron cam follower manufacturers.
They have practically all left the country and set up in places like India, China, Portugal, Turkey etc.