Conquest valve seats

[Phillmore]

I'm currently valve grinding to cure low compression on one cylinder. As I expected the exhaust valve seat was severely pitted with approximately a third of the seat area blackened and pitted. I have now got this down to a few isolated pock marks and as many blisters!. I assume the Conquest uses valve seat inserts or do the valves seat directly into the cast iron head? My question is, is there a point where you shouldn't grind any more due to the thickness of the insert? the width of the seating area has now increased as I grind down but I assume this won't be a problem (maybe even an advantage)?

[theoldman]

Andy,

The valve seats are made of an alloy called Brimachrome and are fitted by being cooled, inserted in to the head and allowed to expand.

I have never known one to fall out!! (have known a valve to bust, mind!)

I would think you will be safe until you start to grind at the cylinder head!!

Neil

[silverfox]

Well,

I did have one drop out in my MkII back in 1970, along the M4 The AA said the engine was FUBAR and that hecouldnt tow me home to north London. Drove home after the tingalinging stopped and did a return trip to Gt Yarmouth and back two weeks later. It burnt a bit of oil!!!!! in the end i was dropping 140sae into the engine. and on the return. Found a scrapper in south London Dad towed it home in his MkI century, me in the toweee and the thing caught fire on London Bridge as the rear brakes had been binding all the way. Anyway Had the engine in this one rebuilt by Roy of Masons ( Dad knew Ben and the boys quite well) and it ran like a dream .In fact had the speedo well into the 90's when i took it over to southern Ireland in 1972. Hankering after getting one again, but needs to be in good nick,( no restoration needed) as at my age i havent got the time!!
And have had conflicting reports on these eing able to run on unleaded without additives true/false?
Ron

[Phillmore]

False I would think but there are far more knowledgeable people on here than me that will answer that question. I use additives in mine.

[theoldman]

Actually, true, as the Brimachrome is "'ard as nails"

I don't use additive in the 104 with a similar set up.

You only really need additive if the valves sit directly on the (cast iron) cylinder head.

[Phillmore]

That's interesting Neil because I was using additives. Practical Classics price guide states not unleaded safe but that doesn't make it fact of course. Is it generally accepted that the seats are hard enough to not need additives?

[theoldman]

Andy,

Additives are a bit "snake oil" - ish on a car which only does a couple of thousand miles a year. By all means stick a drop of Redex in, but unless you are running the car daily for 200 miles at motorway speeds, the valve seats will outlast you.....................

If the engine pinks a bit under load, just drop the timing back a couple of degrees.

Neil

[Fossil]

Is it not true that post war Daimler engines with aluminium cylinder heads and hardened valve seats, including the Century and V8 engines, are safe to be used with unleaded petrol because Daimler used such high quality materials? I switched both the Century and Dart when leaded fuel was no longer available and have never used additives. No signs of mischief so far with a strategy of see what happens and have a spare cylinder head in case. This would be my approach with a car with a cast iron head also, since the mileage done with most older cars is relatively low, in my case around only 1000 miles pa. I don't think the issue is worth any loss of sleep far less a huge amount of expense to have the engine modified, professionally or otherwise.

The Century has done a higher mileage than the Dart for several years, including the DLOC annual rallies at Beamish, Shrewsbury and Anstruther involving long distances and high cruising speeds for hundreds of miles, and is running beautifully as a result. She is just back on the road following winter storage and needed only the tyre pressures topped up before several recent longish runs. Nor has there been any need to interfere with the timing of either engine. With Lumention and HD6 SUs both require minimal regular attention in the ignition and fuel departments. I've always used premium unleaded exclusively, currently Shell V power because by good fortune the town has a Waitrose with attached Shell filling station, but that is more related to the issue of added ethanol quantity. Hopefully this year the Dart will take us to St Ives.

The cylinder heads have come off both cars within the past 5 years for other reasons and there was no evidence of valve or valve seat damage in either. As has been said unleaded petrol is most likely to be a problem for cast iron heads with valve seats cut directly in the head material, so most likely the strict Conquest engine. It is possible although not entirely simple to fit a Century head to a Conquest engine, which would greatly reduce that risk. The inlet and exhaust manifold studs have different spacing.

Regards

Geoff



d

[watkindj]

As "lead" tetra-ethyl lead (TEL or “ethyl”) was only a solution to the knock that early combustion engines had, see the link below
http://www.lead.org.au/Chronology-Makin ... istory.pdf

[theoldman]

Geoff

The "strict" Conquest also has Brimachrome inserts in the head., so no need for additive.

Neil