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robertspark

LPG + Valve Seat Recession + Ford Derived Engines

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I have a question regarding Valve Seat Recession, specifically with regards to ford derived engines.

they seem to suffer from this quite badly, (more than others):

My question is:

Is it just the actual valve seats on the valves that recede, or is it the valve seats (inserts) in the head, or is it both to a similar degree?

The question is a really related to how much head work I will need to have to do, is it just a valve replacement and minor valve lap, or do I need to look at replacing the valve seat inserts in the head as well.

Seems everywhere seems to state that Ford engines should not be converted to LPG because of VSR and their soft seats, but no clarification on which seat is the problem or if both are of a similar issue.

Also is the intake as badly affected as the exhaust?

I understand that the issue is a twofold one with no lubricating properties within the LPG, and also higher cylinder temperatures, hence higher exhaust gas temperatures, flashlube & others aide the lubricating properties, but if you were to use water injection would this not help with lowering cylinder temperatures + its cheaper

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Are you sure they have "soft" valve seats. Basically every motor since the introduction of unleaded fuel has hard seats in them. The lead that use to be in fuel decades ago use to cushion the valves when hitting the seats. Once the lead was removed from fuel they had to build motors with the harder seats.

The lack of lubricant in LPG mainly relates to possible wear on the valve stem and guides, not the seats.

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Running LPG will often lead to burnt valves and seats, whether you need to replace valve and/or seat will really depend on the level of pitting that has occurred. I have seen a V8 which has the hardened seats, after 200,000 miles on LPG with pretty well scrapped valves and seats, but then you wouldn't really mind after that distance, would you? It will really depend on the mileage the engine has done on LPG as to how bad they are.

My dad did over 100K on LPG and suffered no problems until a little end let go -hardly a result of the LPG I am sure! I didn't inspect the valves, as it was sold like it(!)

I think the Ford issue must be down to having hard seats, but not as hard as others.... if they are indeed prone to VSR. Re-seating a head is surprisingly un-expensive actually, I think it was about £100 a few years back for my 2.25 petrol, which whilst you have more valves in the Ford engines I assume, it's still not bad. If you talk to the machine shop they should be able to source harder seats to replace the 'soft' ones in there currently.

What sort of mileage does the rumour mill suggest Ford VSR is so bad you need to repair it?

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Gents,

Thanks for both your replies.

Mileage the rumour mill suggests is somewhere between 20 - 40,000 miles, but I must come a little clean here, and the reason why I posted it in this forum is because some the newer rangerover engines have bee tar'd with the same brush. Through websites such as these:

http://www.amrautos.co.uk/index.php/lpg-systems

http://amrautos.co.uk/database_problem_cars.pdf

Although this is really to do with my 1st car (not the toy) a ford focus (Sigma engine), albeit the rumour mill seems to tar all "ford engines" with this issue, so I was trying to sound out if there was infact an issue with some of the newer Range Rovers etc that may have been converted to LPG that were showing signs or whether this really was just a rumour.... May be a vastly different engine, but I'm sure that they have the same ford bean counter involved in materials purchasing / selection for valves + valve inserts.

For those curious, albeit I am aware that this is off-range rover topic: Carried out a vacuum test, and the intake was running at about 11"Hg at idle, I must admit at this point that I have not carried out anything more intrusive (compression test etc), mileage covered is 88,000ish with about 50ish on LPG. Compression test will follow one evening this week or next weekend. Runs a little rough at idle, but much rougher whilst cold under acceleration up to the 2000 rpm mark, once up to temperature seems to run much smoother, albeit this is the variable valve timing engine, so over 3000 ish rpm it begins to change cam profiles.

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The problem stems from the valve seats not being coated with that old fashioned stuff call TEL  Tetra Ethyl Lead.    Before we had unleaded the valves and seats became coated with a film of oxidised lead which acted as a release agent.   Without lead a soft seat welds momentarily and over time the seat becomes burned.

My Series 3 engine (in a Series 1) was run on leaded for a long time but once we changed to Unleaded in Cyprus the seats started to degrade.    Anticipating this 10 years ago I bought recon head with hardened seat inserts, it is still in the garage wrapped up in grease paper but it is time to do the deed and fit the new head on because Nellie is popping a bit now.

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I did a bit of research when I was buying my L322 about getting a petrol (ford/Jag) v8 engined one and adding LPG.

From what I could gather, they suffered quite badly from valve seat recession problems when run on LPG, even with flashlube. I also read that even running petrol only they could suffer, although at much higher mileages. One of the specialists offered a revalved/seated head with harder materials for running on LPG. 

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