Signs of valve micro welding
Discussion
Finally got round to pulling the head for a valve stem seal job on my series 3 2.25 petrol land rover. Since it was manufactured in 1974 I presume the valve seats wont have been hardened, however the previous owner used castrol valvemaster (lead replacement additive) when filling up, and I was assured that the valves would be fine. Further inspection revealed the exhaust valve seats have small depressions, less so on the intake valve seats. However the valves themselves appear to be ok.
Is this micro welding? And if so, it doesn't say much for lead replacements
Hardened valve seats would be the obvious solution, however I need the landy back on the road soon. Does anyone have a ballpark figure for how much hardened valve seat fitting costs?
Thanks
NonSyncro
Is this micro welding? And if so, it doesn't say much for lead replacements
Hardened valve seats would be the obvious solution, however I need the landy back on the road soon. Does anyone have a ballpark figure for how much hardened valve seat fitting costs?
Thanks
NonSyncro
It looks like a straightforward cast iron head with no valve seats. So a lubricant is definitely needed.
And TBH, I dont think any of the aftermarket products are great at that. And who's to say they were used correctly and all the time ?
Cant comment on "micro welding" as Ive no idea what it is.
Although usually the first problems that occur are losing valve clearances, although these may have been adjusted to compensate over the years ?
What are the valves like ?
And TBH, I dont think any of the aftermarket products are great at that. And who's to say they were used correctly and all the time ?
Cant comment on "micro welding" as Ive no idea what it is.
Although usually the first problems that occur are losing valve clearances, although these may have been adjusted to compensate over the years ?
What are the valves like ?
Yes that's classic unleaded damage on the exhaust seats and pretty bad at that. The inlets just show normal wear and not actually that much of it. They'd probably carry on just fine but you might as well get them and the valves recut while the rest is being done.
Unleaded inserts come as pre-manufactured steel rings from various suppliers such as AE and any engine reconditioner will supply and fit for about £20 a seat. Cheaper and more reliable than petrol additives in the long term. All is explained here.
http://www.pumaracing.co.uk/unlead01.htm
When tests of unleaded additives were conducted in the 90s a batch of Leyland A series engines were dynoed under hard use conditions for 70 hours (maybe 10,000 road miles equivalent) on various fuels and additives and the valve seat recession measured. Leaded petrol showed negligible recession proving what an effective compound TEL (tetraethyl lead) is at preventing micro welding. The pass mark for additives was 0.3mm (12 thou) wear but that's hardly what I'd call a substitute for proper leaded petrol. It's the equivalent of taking up the entire tappet clearance about every 10,000 miles meaning you'd have to adjust clearances at least every 3000 miles or so and ideally less. Unleaded petrol with no additives created a massive 1.2mm of wear in 70 hours running and the cylinder head would have been scrap after just two or three such cycles.
Potassium proved to be the best additive beating sodium, manganese and phosphorus but none of them come close to TEL. The conclusion is clear. Additives work of a fashion and do reduce wear but only hardened exhaust seat inserts provide the long term reliability and absence of wear of leaded petrol with TEL.
Unleaded inserts come as pre-manufactured steel rings from various suppliers such as AE and any engine reconditioner will supply and fit for about £20 a seat. Cheaper and more reliable than petrol additives in the long term. All is explained here.
http://www.pumaracing.co.uk/unlead01.htm
When tests of unleaded additives were conducted in the 90s a batch of Leyland A series engines were dynoed under hard use conditions for 70 hours (maybe 10,000 road miles equivalent) on various fuels and additives and the valve seat recession measured. Leaded petrol showed negligible recession proving what an effective compound TEL (tetraethyl lead) is at preventing micro welding. The pass mark for additives was 0.3mm (12 thou) wear but that's hardly what I'd call a substitute for proper leaded petrol. It's the equivalent of taking up the entire tappet clearance about every 10,000 miles meaning you'd have to adjust clearances at least every 3000 miles or so and ideally less. Unleaded petrol with no additives created a massive 1.2mm of wear in 70 hours running and the cylinder head would have been scrap after just two or three such cycles.
Potassium proved to be the best additive beating sodium, manganese and phosphorus but none of them come close to TEL. The conclusion is clear. Additives work of a fashion and do reduce wear but only hardened exhaust seat inserts provide the long term reliability and absence of wear of leaded petrol with TEL.
Edited by Pumaracing on Saturday 5th November 03:20
You see the strange thing is (and bear in mind I usually agree with Pumas comments) that in the real world I run old engines (mainly A, B, C series and triumph based 1500s) on daily drivers and competition cars. I run lots of other different cars too but these are the ones with cast iron heads and no inserts.
I haven't suffered any recession over hundreds of thousands of miles of varied driving, ranging from sitting in towns right up to fast A road blats and motorway work, with motorsport on a weekend, I just use straight unleaded (supermarket usually) straight from the pump.
I have come across pitting and micro welding of the seats like that picture, but interestingly I've come across it on old engines that haven't run for 20 years and engines which have been running till recently, so engines that were last used on 4 star and engines that have suffered 15 years of crap fuel. I think the real issue is the poor quality material used in the head to be honest.
I always attributed the lack of recession to be down to a rumour I heard (well I know it's true but the conclusion is just a supposition) that the californian spec B series heads were prepared for unleaded fuel not by hardened seats (indeed I know this I have owned one) but a change of cast iron formula for the whole head, knowing BL (here comes the supposition) it seemed unlikely they would have made a special batch of cast iron just for those heads, so I assumed all heads from that period would be UL safe.
That said my current road car is a 1960s MGC and again covering silly mileage with varied use and is well before that period and is again suffering no issues.
So I put a lot of these tests (many of which were sponsored albeit not always obviously by manufacturers of additives) down to the hysteria that existed when leaded fuel was banned, I remember people believing that the classic car scene was all over and no-one would be able to drive their cars, I also remember ridiculous pellets of tin to put in the tank that would magically solve the problem.
My advice with the head above is weigh up how long it has been since it's last head work, if it's been 10k then yes you have an issue seriously consider hardened seats, but if to your knowledge it has never been done then I'd be very tempted to see if it will relap (I have had them lap back in in that state before) and if not get it recut, when and indeed if you start to get serious recession pull the head and get inserts put in, the exception to this being if you do get it recut and it works out not much more to get inserts put in common sense would be to get them put in.
In other words try to save some money because my gut feeling is this isn't the end of the world.
I haven't suffered any recession over hundreds of thousands of miles of varied driving, ranging from sitting in towns right up to fast A road blats and motorway work, with motorsport on a weekend, I just use straight unleaded (supermarket usually) straight from the pump.
I have come across pitting and micro welding of the seats like that picture, but interestingly I've come across it on old engines that haven't run for 20 years and engines which have been running till recently, so engines that were last used on 4 star and engines that have suffered 15 years of crap fuel. I think the real issue is the poor quality material used in the head to be honest.
I always attributed the lack of recession to be down to a rumour I heard (well I know it's true but the conclusion is just a supposition) that the californian spec B series heads were prepared for unleaded fuel not by hardened seats (indeed I know this I have owned one) but a change of cast iron formula for the whole head, knowing BL (here comes the supposition) it seemed unlikely they would have made a special batch of cast iron just for those heads, so I assumed all heads from that period would be UL safe.
That said my current road car is a 1960s MGC and again covering silly mileage with varied use and is well before that period and is again suffering no issues.
So I put a lot of these tests (many of which were sponsored albeit not always obviously by manufacturers of additives) down to the hysteria that existed when leaded fuel was banned, I remember people believing that the classic car scene was all over and no-one would be able to drive their cars, I also remember ridiculous pellets of tin to put in the tank that would magically solve the problem.
My advice with the head above is weigh up how long it has been since it's last head work, if it's been 10k then yes you have an issue seriously consider hardened seats, but if to your knowledge it has never been done then I'd be very tempted to see if it will relap (I have had them lap back in in that state before) and if not get it recut, when and indeed if you start to get serious recession pull the head and get inserts put in, the exception to this being if you do get it recut and it works out not much more to get inserts put in common sense would be to get them put in.
In other words try to save some money because my gut feeling is this isn't the end of the world.
Firstly, no don't even try lapping seat damage that severe out. Read this.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Secondly, many iron head engines will run quite happily for thousands of miles on unleaded as I say quite specifically in my website article. It depends on the severity of use, how much the seats have work hardened in use prior to swapping to unleaded and also the grade of cast iron which is always an unknown variable.
The OP's exhaust seats are badly pitted due to micro welding but they aren't actually recessed and that usually only happens under severe use and with engines that run very hot. I wouldn't expect a lowly tuned Land Rover engine to fall into either of those categories and if the seats were recut it might well go another 50,000 or more miles before needing more work. However seeing as the head's already off, the cost of gaskets and that fitting inserts will only add maybe £50 to the cost of the seat cutting needed anyway it would be foolish not to do it and have peace of mind for ever after.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Secondly, many iron head engines will run quite happily for thousands of miles on unleaded as I say quite specifically in my website article. It depends on the severity of use, how much the seats have work hardened in use prior to swapping to unleaded and also the grade of cast iron which is always an unknown variable.
The OP's exhaust seats are badly pitted due to micro welding but they aren't actually recessed and that usually only happens under severe use and with engines that run very hot. I wouldn't expect a lowly tuned Land Rover engine to fall into either of those categories and if the seats were recut it might well go another 50,000 or more miles before needing more work. However seeing as the head's already off, the cost of gaskets and that fitting inserts will only add maybe £50 to the cost of the seat cutting needed anyway it would be foolish not to do it and have peace of mind for ever after.
Edited by Pumaracing on Saturday 5th November 19:29
I should add something else for the sake of completeness. The MIRA tests on additives were conducted using brand new cylinder heads donated by Rover. The importance of this will become clear shortly.
Cast iron is a very strange and fascinating engineering material that you could, and many people do, spend a lifetime studying. It is fairly soft in the as-cast state but it can be flame or induction hardened, or indeed chill cast in special cooled moulds, and can achieve very high hardness values which resist wear better than most steels. The bedways of lathes and milling machines are usually induction hardened and you'd struggle to scratch them with a sharp file which are hardened to at least 60 Rockwell C.
When an engine with a cast iron head runs for extended periods the combustion heat flame hardens the exhaust seats to some extent and the harder the usage the harder the seats get. So an engine that's had the arse ragged off it for years on leaded petrol might run happily for ever after on unleaded. An engine that's only had light use or that doesn't get very hot anyway because it's in a low state of tune might do less well. Brand new heads are the worst possible case because they'll have no hardening at all and if you cut the seats on an old head you'll remove the hard layer and be back to scratch anyway. So the Mira tests on new heads were worst case scenario but what they did prove was that aftermarket additives are nowhere near as good as TEL.
So I'm not at all surprised when I hear about old engines that run quite happily on unleaded but if the OP has the seats cut, which it definitely needs, then they might wear out again a damn sight quicker than they have done so far because the hard casing will have been removed and they'll be back to the as new condition.
So for the cost of a few bottles of not totally reliable additive steel inserts make the most sense.
Cast iron is a very strange and fascinating engineering material that you could, and many people do, spend a lifetime studying. It is fairly soft in the as-cast state but it can be flame or induction hardened, or indeed chill cast in special cooled moulds, and can achieve very high hardness values which resist wear better than most steels. The bedways of lathes and milling machines are usually induction hardened and you'd struggle to scratch them with a sharp file which are hardened to at least 60 Rockwell C.
When an engine with a cast iron head runs for extended periods the combustion heat flame hardens the exhaust seats to some extent and the harder the usage the harder the seats get. So an engine that's had the arse ragged off it for years on leaded petrol might run happily for ever after on unleaded. An engine that's only had light use or that doesn't get very hot anyway because it's in a low state of tune might do less well. Brand new heads are the worst possible case because they'll have no hardening at all and if you cut the seats on an old head you'll remove the hard layer and be back to scratch anyway. So the Mira tests on new heads were worst case scenario but what they did prove was that aftermarket additives are nowhere near as good as TEL.
So I'm not at all surprised when I hear about old engines that run quite happily on unleaded but if the OP has the seats cut, which it definitely needs, then they might wear out again a damn sight quicker than they have done so far because the hard casing will have been removed and they'll be back to the as new condition.
So for the cost of a few bottles of not totally reliable additive steel inserts make the most sense.
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