How easy is an unleaded conversion?

Message

John Weston · #1 Post by **John Weston** » Tue Jan 22, 2008 10:21 pm

I\'m about to take the head off my 2000 ( and 2500S later ) to get them both on unleaded...... how easy is it to source parts and have the valve guides/seats pressed in again? Or is it really too much of an effort and easier to go directly to CW - and instead paying to get out of this? I have a local friendly garage and machine shop - but don\'t want to bother them if it\'s a nightmare job. Thx John

#2 Post by **Alan Chatterton** » Tue Jan 22, 2008 10:34 pm

Good Timing..............
A member (and friend of mine!) is having his head of his 2500S converted now.........
Being done at an engineering shop in the Warwickshire area by an \"old School\" shop. Bloke reckons hes been doing conversions for years and always been fine.
Replacing all 12 guides, 12 seats and 12 valves.......cost estimated to be about £200!
I reckon this sounds good.
The head is due back in about 10 days, and if it is any good, he can do mine too!
Keep you posted when we see the work........
 

#3 Post by **David Withers** » Wed Jan 23, 2008 4:20 am

Hello John,
The first question should be: \"Do I need to convert?\"
Our cast iron heads aren\'t as soft as some, such as the BMC \'A Series\', and if the engine has run for several thousand miles on leaded fuel since the valves were last lapped in, there will be lead deposits (\"lead memory\") on the valve heads and seats which will generally allow thousands of miles running on unleaded fuel.
I wrote a quite comprehensive article on this for SIXappeal a couple of years ago, and this is not the place to repeat everything.  The following is just a summary:
Valve seat recession is caused by hard deposits becoming welded to the valve head and acting as cutting tools during valve rotation (valve rotation being a deliberate feature of the engine so as to even out wear and heat transfer).
However, if the engine speed doesn\'t run above 3000-3500 for long periods and the engine doesn\'t get overhot by towing caravans up hills etc., there is every chance there will be no recession even with unleaded fuel and no additives.
It may be that your 2000 is a stronger candidate for conversion than your 2500 as it is an automatic and hence will probably run for some miles on the open road at above 3000 rev/min.  I converted my 2500 from auto to manual+O/D ten years ago specifically to avoid this, the gearing in O/D top now giving me a fast enough 80mph at 3000 rev/min.
I\'ve run my 2500 for 12,000 miles on unleaded without any problem, and I don\'t hang about.  I very often take excursions above 3500 rev/min, almost every time I go through the gears on the open road in fact, but I don\'t hold it there for long periods, and neither do I tow.
I do keep watch on the valve clearances (\'tappets\') as any closing of a gap could mean that the valve is starting to sink into the seat.  So far there has been no measurable gap closure at all, as measured with feeler gauges.
No warranty given or implied, but you could be OK as you are!
 

#4 Post by **sorbs** » Wed Jan 23, 2008 5:21 am

My 2000 auto is geared at about 20mph / 1000 rpm, so motorway driving sees engine speeds of well above 3000 rpm for prolonged periods.
I normally use an additive, and in the last 7000 fairly hard driven miles, haven\'t noticed any valve seat recession.
All the same, if you have the opportunity of fitting hardened valve seats, it can do no harm.

#5 Post by **Alan Chatterton** » Wed Jan 23, 2008 5:28 am

Very True.
The only reason I am having mine done is becuase at 150k, then engine is in need of work. The valve guides are worn, so, if they need replacing, now is the time to upgrade to unleaded.
Havig said that, I put it back on the road in 1998, since then it has done about 30k hard use (CT Round Britain, high speed motorway cruises and tows a BIG caravan...........) and never had a problem despite never using an additive!
 

#6 Post by **sorbs** » Wed Jan 23, 2008 6:05 am

Great these big Triumphs.
My \'69 saloon was off the road since \'99, but passed it\'s MOT with no issues two years ago and has had the living daylights caned out of it by all and sundry ever since! It\'s such a good car.
The brownmobile (saloon) has 75k miles on it, and the new estate 89k - barely run in!

John Weston · #7 Post by **John Weston** » Wed Jan 23, 2008 2:25 pm

I\'ll sit on that for a little while then - although I do think the engine is in need of a general overhaul anyway so it\'ll be on the list. I\'ve been running on unleaded without issue too - but was interested in the projected conversion costs. Will be good to hear back on the work done..... postage may add to that total though <img> I\'ll keep it stock for now and see what state the rest of the engine is in first........ Before  dig out the workshop maunal - what\'s the expected compression ratio on the 2500S? Thanks a lot everyone.

#8 Post by **Alec** » Wed Jan 23, 2008 2:43 pm

Hello all, unless you know the head is worn and needs remedial work, I would not pull a head just to modify for unleaded. Wait until it is showing signs of needing attention. By the way, 6 inserts are all that is required, valve seat recession only affects the exhaust due to the high (relative) temperatures they work at. Alec

#9 Post by **David Withers** » Wed Jan 23, 2008 3:00 pm

Just to make it clear, the 3000+ rev/min I mentioned is a generalisation for most iron head cars, not just Triumphs, and the amount of overheat that will cause damage will also vary as different engine designs allow different rates of thermal exchange between valve seats and coolant.
The Triumph 2000/2500 head is better than many but when failure does occur I think it is likely to be fairly quick.  The engine could be OK when you leave home but once the valve starts to chew away at the seat it won\'t take long for the tappet clearance to disappear and the valve then be unable to sit firmly on the seat, at which point the hot exhaust gases will help finish the job as they squeeze by.
I agree with Alan that it\'s a good idea to convert the head to unleaded spec when it becomes in need of overhaul but I would never risk hard driving for any significant distance with a caravan on the back under the circumstances he describes.  Lucky for some!
I\'m pleased no-one has recommended those absolutely useless fuel catalyst gimmicks.  If only it hadn\'t been agreed that the identity of the catalysts and additives failing the FHBVC/MIRA/Rover \'unleaded head\' tests should remain confidential!
But we do know only to use additives carrying the FHBVC mark of approval, don\'t we?  And we also know that not one of the so-called catalysts carries the mark, don\'t we?
 
 <edited><editID>Dizzy</editID><editDate>39473.903587963</editDate></edited>

#10 Post by **David Withers** » Wed Jan 23, 2008 3:30 pm

Good reminder, Alec, that only the exhaust seats need doing.  They also need to be done by someone who knows what they are about of course.
A few years ago I called in on a local engine reconditioner to pick up a T2000 crankshaft I\'d had ground.  While I waited I watched a chap fitting some inserts, which were such a loose fit that he proceded to Loctite them in!  That wouldn\'t have lasted five minutes!
I casually asked him if he\'d had to serve an apprenticeship for the work he was doing and he replied \"no, I\'ve only just started doing mechanical work\".  I then asked him what his previous job was and he said he worked with the elephants in Billy Smart\'s Circus!  I thought he was joking but the look on his face said he was serious!
All was confirmed when I checked the crankshaft they\'d just ground.  The surface was as rough as @*#~holes. \"It\'ll soon bed in\" I was told and a long and bitter dispute followed, only partly ever resolved.  To give you an idea of the surface finish of the reground journals, I checked them back at work and they were \'milled\' finish (I forget the actual Ra figure).