| Author | Message | ||
     RayWhite Unregistered guest Posted From: 86.134.91.41 |
This is my first post on this forum ...but I have read the entire EPW content and learned a lot.! In my search for information regarding the Mark 6 have also read all the technical guidance notes from Norman Geeson on the Ashley James blog. However, the more I learn, the more I realise how easy it is to buy a car with serious - but hidden - problems. It seems to me that there are those cars which have been cosmetically restored and look beautiful but have mechanical issues and other cars which may look neglected but in fact have a good service history. There are some cars offered for sale (often at very high prices) that are in excellent condition all round but they tend to get into the hands of car dealers who are only interested in turning a large profit. As a consequence of researching the Mark 6 I have established some pre conditions. The first is I will not entertain a car that has serious corrosion. The damp British climate and heavy salting of icy roads here means rust is always a consideration. The last two cars which I have restored have been imported from Australia and have had no such problems. Australian cars, however, have to contend with much higher temperatures and it is my understanding that over heating is a common issue especially if the engine is silted up. Another issue that worries me is the use of chrome cuff liners in the engine. I remember my late Father getting hot under the collar about a Mark 6 engine which had suffered broken piston rings due to these short chrome liners. Just how much of a problem is this? I am also quite keen that the rear axle is quiet and the wheel bearings have been properly replaced. A higher ratio would also be a big bonus. I know there are many other issues to consider - and don't get me wrong; I would love to own one of these magnificent cars - but I want to make sure that if I buy one I will not end up regretting it. Do you guys have any suggestions? (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 4251 Registered: 04-2003 |
First of all, welcome to our forum and we trust you will find our contributing members most helpful in guiding you to find and maintain the car of your dreams. My first suggestion is to join the UK Rolls-Royce Enthusiasts' Club if you are not already a member as this would be the best starting point to finding a suitable vehicle as both the provenance and condition of the vehicles owned by members is usually of a better standard than those offered by the second-hand car trade. https://rrec.org.uk/ At the end of the day, the old adage "first cost is never the end cost" prevails and my advice is twofold: 1. Have the car thoroughly checked by a Rolls-Royce EPW specialist - our UK EPW forum contributors may be able to suggest one or more specialists for this purpose close to where a vehicle that you are interested in is located . 2. Be prepared to probably spend more than what you anticipated to get the "right" car for you; "quality doesn't cost - it pays" as the old saying goes. You might find our Australian free access RR&B technical library useful for specific information on EPW R-R/B vehicles. https://rrtechnical.info/ Best wishes for a successful search for the right car for you.  | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 597 Registered: 07-2018 |
About the chrome liners, I never really agreed with the hour glass wear problem causing the top rings to break. I bought my car on an impulse and with out knowing it, all the top rings were broken and compression was down to 60psi right across the board. The odd thing is that the bottom rings, were not broken, why was this, surely if the irregular bore broke the top rings, why not the bottom ? Never got an answer to this, and I believe the "broken" ring problem is to do more with a heat dissipation problem more then anything. Chrome, (and stainless steel) doesn't dissipate heat very well, so if a car is over heated the top of the bore gets very hot and a given liner is not very efficient on getting rid of heat. Plus the problem of heat transfer from the liner to the block also adds to this problem. This in turn starts heating up the top rings beyond their spec and the ends come together where the rings fail and break. The bottom rings are not affected because they are not so near where all the heat is, this explains why the bottom rings were not broken on my car, and I'm going to say others. Granted if one measures the bore, it may not be parallel anymore, but not enough to break the bottom rings, so why the top ? I know of a car where the ring bits were bouncing around in the combustion chamber, and even parts of the piston, but the bottom rings were still in tact, surely a bore so bad would have broken the bottom rings, but they were still in tact. I have a 4.5 litre engine that an "X" club member gave me and it still has the liners in them, and all the rings are intact. The car was driven happily until a fire destroyed the body in the owners drive way. That same club member has a Dawn with a 4.25 litre engine where he bored it out with the liners still in it with over-sized pistons. His father purchased it new and 20 years after the rebore the engine is still going strong. My car was not silted up, but I'm pretty sure it was over heated at least once, probably many times, as I found the thermostat was butchered to allow coolant to flow through all the time. This actually made things a little worse because the by-pass remains permanently open reducing the cooling efficiency of the car, so on hot days it may have been near being over heated beyond spec. If my theory is correct, I don't think an engine would have to be over-heated much to break the top rings, even if only one crack occurs from the ring ends coming in contact with each other, that's all it would take to eventually have a complete failure. In the end my car was bored to accept full sleeves and was brought back to spec with a bore of 3.5 inches. . | ||
| ChristopherCarnley Unregistered guest Posted From: 109.157.94.79 |
The perceived problems caused by the chromard liner are total rubbish. The broken piston rings are due to condensation corrosion eating away the piston ring grooves, which enlarge allowing the cast iron rings to smash themselves to pieces. There are no ridges. The "high ratio" gears are are a misnomer. A change from the standard 11:41 to the Continental 13:40 is a ratio reduction, but it gives higher gearing. Higher gearing leads to less acceleration from rest, but higher top speeds. (Message approved by david_gore) | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
David. Thank you for your advice. In some ways it is not quite what I was expecting and has made me think. I have always imagined that buying a car from a club member would be the more expensive option as they would probably have a better idea of market values than perhaps a private seller who, for one reason or another, has lost interest... and just wants the car out of the way! On the other hand, a Club member is perhaps more likely to have kept up a maintenance regime and, as you say, their cars probably have better provenance. One car I was interested in recently (B40PV) was sold at auction for £38K. It was advertised by a dealer for an unrealistic £55K but he chose to move it on. I had read the restoration blog by former owner Giles Usher in which he details modifications such as a Norman Geeson rear axle and a 4.9 S1 engine by Ashley James. This car was described as a Mark 6 with a twist!. I tried to get a deal together trading my 1930 Austin Swallow saloon and 1949 MG TC (unfinished project) but it was not to be. I really need to finish the MG before getting another car; because of this, I didn't bid for it. I believe it was Henry Royce himself who said " the quality will remain when the price is forgotten" and that is so true. The one underlying issue that keeps me holding back are the cuff liners. In fact if I find a car that is otherwise reasonable I would probably not proceed. Is it an unreasonable expectation that full length liners have been fitted or a substantial price adjustment be made? (Message approved by david_gore) | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
Jeff. Thanks for your input which, from my point of view, has muddied the waters even more than before. Now I don't know what to think. I would venture to suggest that if a ridge occurs due to the different wear rates of cast iron and chrome, then logic would have it that the rings will eventually break. Having read your explanation regarding heat dissipation I am even more reluctant to buy a car with them still in situ. To be frank, I don't much care how the breakages are caused; I just know you are in trouble if they do, because a re bore with chrome cuff liners (even if you can find someone to do it) will not last long and a set of new liners will not come cheap. I understand from my research that chrome cuff liners have been blamed for piston ring breakage right from the start but the problem became even more pronounced with the 4.5 litre... and this was obviously know to Crewe as they tried to correct the problem. It is interesting to note that dealers will go to any lengths to avoid the subject. It is as if the 4.5 litre engine in particular has a dark secret that has to be avoided. Having said that, it is difficult to glean any worthwhile maintenance history from any dealers adverts. Norman Geeson described the situation as "catastrophic" and I would hesitate to argue with him on Bentley matters.! (Message approved by david_gore) | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 598 Registered: 07-2018 |
Thanks for that Chris, I have never come across that explanation, but I like that one better then mine, that would also explain why only the top rings are broken and why some cars who have the chimney liners are unaffected. I would think this happens to cars where they haven't been stored properly for very long periods of time. Ray, and engine is engine, don't over think it, my Dad had this old Ford Meteor that was so worn, that it had to be parked on this steep hill where my parents lived at the time to get it to start. The bores had a deep ridge at the top, and the rings were worn, but they weren't broken. An engine so worn on the landings where the rings break, will have other issues to keep you from purchasing. Very little wear occurs where the cuff liner joins with the cast iron. Remember too, my explanation is just a theory, I would believe Chris before me as he has so much more experience then I. The biggest problem with these cars (any car) is they sit with old coolant in them, and that's where the trouble starts, or owners who don't change the coolant or worse, they just run water. I did say that an "X" club member did have a Dawn that belonged to his Father where the Son rebored it with the liners in, and it's now been 20 years (longer now too) It's still going strong. His name is Tom Mellor and he lives in North Vancouver here in Canada on the South West Coast of B.C. The 4.5 litre can be more susceptible to over-heating because of the siamesed bores, but you know that if you've read Norman's articles. Once silted up, the back of the block gets cocked up and coolant can't flow there. The 4.25 liter engine has spaces around all the bores, but the head on it has poorly designed combustion chambers that causes the exhaust not to flow properly. They fixed this problem in the 4.5 litre head, but they are not interchangeable to the 4.25. Look for a car with a full flow oil filter too. Once you get to a car you like, the owner should have no problem letting you see if coolant will flow from the pet-cock at the back of the block. If it doesn't, walk away. A compression test will show if the rings are broken, it should be at around 115 to 120 psi. My engine with new pistons, valves and full sleeves is at 115 psi at 21,000 miles _ and that's normal. | ||
| David Hughes Experienced User Username: wedcar Post Number: 162 Registered: 07-2004 |
Ray Send a message to Bill Vatter in the U.S. Regards David | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
How about the S1 engine transplant? The car I was interested in had been thus modified and not withstanding a considerable power increase, it gave rise to a few questions to which I never did get a satisfactory answer. One thing that was pretty obvious was the exhaust manifolds had been altered to fit. Another was: with the 4.9 litre S1 block being physically longer than the original 4.5 litre it was very close (maybe even touching) the bulkhead. I queried whether this interfered with the for/aft adjustment of the gearbox and could it give rise to gear selection issues. ? Another modification was the fitting of electric power steering. I was a bit concerned that this might be masking wear. Is this a common - or even worthwhile - addition to a Mark 6 ? (Message approved by david_gore) | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 600 Registered: 07-2018 |
I think the blocks are the same length over-all, the cam shaft UE3736 from an S1 (4.9) is the same length as an RE19517 from my 4.25 which also fits the 4.5 litre. They're both 27.125 inches in length. (use your scroll wheel to enlarge the copies) https://1drv.ms/i/s!Ak1aw8qrdXdhwCHeMW8JdO8jW4sd?e=EAfzVT https://1drv.ms/i/s!Ak1aw8qrdXdhwCCKpQsNp4xXI5z0?e=HCtXLL I'm going to say the block was sitting close to the bulk head because the front mounts on the S1 4.9 are on the side of the block, while the 4.5 and 4.25 is mounted from a single mount on the front timing cover. If the timing cover was used where it allows the single mount at the front, it probably would not have been so close. I'm sure someone will correct me if I'm wrong. Go back and look at that car and see how the engine is mounted; at the front or on each side. | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
Thanks for your advice, Jeff. If only I had finished the rebuild of my MG TC I could have bought that car. No doubt, if I had done, I would still be here asking questions ...but just different ones!! As it happens, B40PV was sold at auction for £38K. I would not want to pay much more for ANY Mark 6 standard steel saloon; indeed I have seen one or two nice cars for less. As it happens I am restricted to 16 feet so an R type will not be of interest which limits the field somewhat. (Message approved by david_gore) | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
I have yet to be able to send a message to anyone on this forum. Sorry, I am not very good with computers. (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 4252 Registered: 04-2003 |
Ray, Just fill out the free membership link and you will have full access privileges including sending messages to other forum members. This involves clicking on the REGISTER button in the top right hand corner of any forum page and then answer the prompts. The Forum Administrator will approve your membership and you will then have access to all the forum facilities including messaging. | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
Hi David. I have tried what you suggested. Two problems. 1) I am unable to fill in the password boxes - it won't let me 2)It says the username that I chose - Raymond- is already in use and I need to choose another one. Yes, it was me using it and it was accepted the other day in an email from you as far as I know. (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 4253 Registered: 04-2003 |
Ray, You will have to submit this to our Administrator as I do not have access to the forum user names register. Please use the link below and complete the relevant details requested: http://au.rrforums.net/cgi-bin/forum/board-profile.pl?action=register&coppa=ok | ||
| Jason Watson Experienced User Username: crikeydawn Post Number: 114 Registered: 07-2023 |
Ray, I am an outsider so to speak and only been around these cars for maybe 4 or 5 months. I'm not in a club but the last classic car I was involved in, I found there are opportunists in car clubs as much as anywhere else. I had thought trying to buy through family I could do better, but found crucial info was also withheld around its supposed untouched originality. The guy I bought my car off who has done a concourse car or two, believed if it had not had a chassis up rebuild, than it will need one. I paid 23k for a dried out flooded car in 1000 bits that had something a little different, and here's why. The math around these cars doesn't add up in most cases unless you are playing with coach built. Even then its the same just cost are higher. If a complete rebuild is conducted on a standard steel via the usual cheque book paths one may spend 100 to 150k on top of purchase. The only cars that come close to matching that in value are the coach built. I don't see a restored standard steel selling for 100 let alone the 200 it has cost including the purchase. I was looking at a standard steel low kilometre 2 owner Silver Dawn long boot with colonial spec that was very original with all the papers and tools. Perfect interior, never driven in the rain bla bla bla. 50k didn't bag it and I'm now glad it didn't. At 69 years old, paint, chrome, rubbers, brakes, woodwork, chassis, will all need attention. Then it had heating issues from not being driven enough, and minor damage that had been repaired from 2 different events was poorly disclosed. So forget about that bit of never been driven in the rain. That car however has a potential end cost of 200 and may fetch 70-80 on a good day in concourse condition. That is if we all wish to own and drive the worlds best motor car in the condition its accustomed to. On the flip side these beautiful cars were never around in huge numbers, so they are worth something. Its the history for me that is its real worth. Sadly they have diminished by 1/3+ and I feel its largely due to unreasonable inflated running costs. I have found there is a rather high tax on parts or labour simply because its a RR-B. The same part that may fit a MG or Citroen can cost multiple times less if sought through non RR-B channels. There is some good engineering around these cars, but also poor. Engine sleeves is one, siamese cylinders casting another, and I'm confident there will be more. They are in many ways just nuts and bolts like every other car. I'd debate the value remains long after the price has been forgotten has some truth, but more so a marketing contradiction these days. Its clear from the condition many cars find themselves in, they are not 3 or 4 times better than then original sale price suggested. Rather its clear up keep costs are disproportionately high compared to its retail value, and appears to have been a thorn in the side of many owners. So poor maintenance begins which eventually leads to parting out vehicles becomes an easy path. One that is more profitable than a half baked resto, and less daunting than a proper. So for my opinion for what its worth. These are beautiful cars and worthy of your interest, just don't use rose coloured glasses to view them. Buy some good bones for under 25k, and restore it yourself with labour who will let you work along side if that is your will. That way you may have a finished car in fine condition for hopefully what its worth. Or happily pay a very high price for a car you are 100%+ sure has had a very thorough rebuild less than 20 years ago, and then driven 10,000+ kilometres per year since. I think outside of that you don't have to buy one. Or if you do just enjoy it, pay the upkeep, and don't ponder on outgoings. You see this often, cars with 50k of receipts selling for 30. Quite sad really. . | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
Getting back to the subject. We know there are many supposed reasons for piston ring breakages. That condensation might be the cause is a new one on me ...and I have been around engines all my life and I am nearly 70. My Father ran a garage and was convinced that nearly all the broken rings in Mark 6 engines that he saw were caused by the short (Brichrome 30%) chrome liners. The different wear characteristics of the two metals are incompatible and he did sometimes find a ridge but these were not cars that had sat idle for long periods; they tended to be driven regularly ; some - but not all - had covered high milages. Normally, when rings fail it is due to wear. Taper in the cylinders cause wear in the piston grooves allowing the rings to move in and out and twist up and down. ...or overheating; causing the top ring to close it's gap to the point where it has nowhere to go but outwards and break as a result. I suggest this excessive heat would have been exacerbated by the chrome surface being particularly poor at oil retention and heat dissipation. As it happens, one suggestion I have heard that may help to conserve the top rings in engines where cuff liners are still present, would be a good shot of upper cylinder lubricant; like the old Redex that used to be available at filling stations. I expect a dash of Diesel in the petrol would have similar benefits. In the end though, one has no idea if, or when, the rings might fail as a result of a poor engineering design that was eventually discarded. (Message approved by david_gore) | ||
| ChristopherCarnley Unregistered guest Posted From: 86.183.174.254 |
B40PV, owned previously by both Terry Unwin and Giles Usher has a "bitsa" 4.9 litre engine with a MK VI sump. Built by a well known site holder, this work is well documented. The extra heat from the 4 ring pistons has to be witnessed. The ill informed suggestion that the piston travel over millions of cycles in the MK VI engine suffer colossal damage due to micro variations between the parent iron and the chromed top liner is alarmist fantasy. There is not a shred of physical evidence. (Message approved by david_gore) | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
Many thanks Jason. I feel we are on the same page. I have restored quite a few cars over the years...and not just superficially but chassis up last nut and bolt jobs. Until just recently I have been able to scrape by and just about break even but my latest project has turned into a money pit. I bought a 1949 MG TC which looked to be a good running resto until I got it home and found out the truth. I had been sold a lemon. The new interior trim was hiding a rotten Ash frame; the "new wood" was basically firewood. That was just the beginning of the clever deception which had even fooled so called "experts" from the MG car club. Cutting a long story short I should have sold it on immediately but my pride got in the way and I embarked on a rebuild to beat all rebuilds with every upgrade going and I now have receipts for nearly £50k on top of the purchase price for a car that will probably not reach £40K no matter how good it turns out. I foolishly allowed myself to wear those rose tinted spectacles when I should have walked away. I won't be making that mistake again. The Mark 6 I said I was interested in had been subject to a very expensive and thorough restoration and sold for £38K at auction. That's the sort of thing I am looking for and in today's world it could just happen again. If it happens it does; if not, then it's probably not supposed to. I have hankered after a Mark 6 ever since seeing them in daily use and would love to own one ...but it has to be the right one. (Message approved by david_gore) | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
ChristopherCarnley. The last thing I would wish to do is spread alarmist fantasies!!!!!!! Let us assume you are right and the cuff liners are not the cause of top ring breakages, do you suppose condensation corrosion of the ring grooves affects only these engines... or have you evidence that it is commonplace? If so I would very much like to see it. As I like to say, one is never too old to learn. (Message approved by david_gore) | ||
| Jason Watson Experienced User Username: crikeydawn Post Number: 115 Registered: 07-2023 |
Ahhh sorry to hear that Ray. You are not the only one and I'm sure many on here have a similar experience. I know I have. Good on you for having a go at saving it, many would have just parted it out. What got mine in the garage was it had manuals, suspension, gear box, radiator, chassis, already done. The motor is also done just needs assembling. The upholstery is surprisingly good for a car that has had a swim, but I will still change all the padding due to its age. I hope it all works out for you | ||
| David Gore Moderator Username: david_gore Post Number: 4256 Registered: 04-2003 |
Christopher Carnley has provided the following contribution for me to post on his behalf: "The first question is, Ray, have you ever witnessed the ridge? This idea comes partly from the older plain iron blocks which had worn bores, and a ridge at the top. New ring sets used instead of a rebore had special ridge dodger top rings. In the early years of the MK VI, specialist retailers and others would bore out for the chrome liners, but a very few left a tool point fillet at the bottom such that a small gap was left between the top liner and the bore. Evidence for ring damage here is more anecdotal than real. The post war engine up to 1955 is almost unique in having this liner, designed to give 100,000 miles before first major overhaul. Many cars were short journey and the engines rarely got hot. These parts shown come from a 1953 R Type engine B205U, rebuilt by me with assistance from the capable owner and my assistant Dan, with the tats. The car had been stored at 62,000 miles for about 48 years. It was resurrected by a former specialist, turned unrepentant scrap dealer. The mileage is genuine as I rebuilt the gearbox, found to be in as new condition. The main shaft was renewed for the thicker 3rd speed thrust washer. He had taken the pistons out due to heavy oil consumption and low compression. All of the top rings were in fragments, the grooves had corroded oversize, so he had the grooves machined and fitted double steel rings to compensate. The dotted line is to show my client where the actual contact faces are. He had attempted to remove the head studs for a rebore, but they were too tight. Dan is shown removing the studs with a Stillson type pipe wrench. The broken rings had scored the bores which were treated to a Service Manual rebore and hone and new + ,010" pistons. The nonsense, new, full length soft Meehanite iron liners are not used."    | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 601 Registered: 07-2018 |
Isn't that pipe wrench a little barbaric, I think there should be at least a piece of wood or some heavy card-board to protect the deck ? I use this from Snap-On, the M10 1.25 (from memory) fits the BSF threads well enough. https://shop.snapon.com/product/Stud-Remover-Set-Components/M10-1.25-Taper-Collet/CJ500-42 About those RR pistons with their soft alloy and that deep skirt. I had some modern forged custom pistons made up with a short skirt. Modern alloy is where it's at. | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
Jason. Thank you for your kind words and encouragement; I need it! This "originality" thing is something of a misnomer, isn't it? I have seen a couple of early cars advertised. I know that a 1947 Mark 6 would originally have eschewed spats over the rear wheels; indeed there are no wing fixing points for them... but on one car I noticed they have been added...as has the chrome trim on the doors. The giveaway, of course was the interior. The early cars had plain - as opposed to pleated - leather seats with no pull down tables in the back. Indeed the very first ones had rather nice front arm rests that were later omitted. The passenger side also has the quick action window lever. I am sure there are many other details but originality can be quite tricky to get right. Of course, I am reasonably familiar with the differences between the 4.2 and 4.5 litre cars. As the Mark 6 is just 16 feet it fits my garage nicely so dismissing the R type has limited my options somewhat. Another early car I have seen advertised belonged to someone whom one might have expected to get things right. However, while it correctly had no spats or chrome side trim, the interior had been re done with pleated seats and (sadly) contrasting piping. I don't know why people do this. It's a personal thing but I sometimes cringe at gaudy piped seats. Then there is the problem that some trimmers - despite generally doing good work - lack attention to detail. One irritation seen on some very expensive offerings has been (where pleating is appropriate) the rear seat back and base pleats don't line up. That makes for a potentially expensive correction and one which would limit my interest. Of course, I like a nice original car but some sellers confuse genuine patina with sheer neglect. If one considers - that due to our climate and salt laden icy roads - many British survivors have been at rock bottom at some point, that they have survived at all is, in my opinion, more due to their faded glory than anything. A thorough under body examination may not be possible but I have an idea that a good root about in the boot might expose terminal corrosion. In particular, I have seen a near side rear inner wing rusted through. It may hidden by carpet so I would get permission first - but I would take a look in there!. I would assume a mechanical restoration is likely even if the records suggest otherwise. Garages, as I know from my own experience, don't always get it right. Some take short cuts and others can actually leave things in a dangerous condition. I spent the 1970s working in a garage (unfortunately not my Dad's one) and saw things done that would make your hair curl.!! . (Message approved by david_gore) | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
Let me in the first instance remind readers that I am making assumptions, not based on first hand experience, but on the research carried out Norman Geeson who, in my opinion, has as much - if not more - experience of these matters as anyone. I am referring to page 8 of his technical guide in the Ashley James blog https;//kda132.com. which is the section dealing with the crankcase and liners. I quote: "the efforts, from 1948, to almost eliminate top end bore wear by the use of these short Brichrome 30% chromium liners was catastrophic to piston rings. Wear steps also occurred at the joint of the liner and lower parent bore, causing piston ring breakages. This was due to the difference between the hardness of the liner and the natural cast iron lower bore. The step was actually present, albeit only to a small degree, when the engines were produced. Little wonder that service life was found wanting. The plagues of piston ring breakages and ring scuffing were well known from inception." My own personal experiences are limited to a memory of my Father (an engineer of some standing) who ran a small garage for 'selected' customers back in the 1960s. He knew his way around a Mark 6 (amongst other better quality vehicles) and I remember him talking about these short liners being responsible for piston ring breakages in otherwise good engines. If the above has been comprehensively disproved then it removes a sizeable obstacle in my mind which has for many years been only equalled by tales of woe regarding overheating due to a misguided reduction in fan size. . (Message approved by david_gore) | ||
| ChristopherCarnley Unregistered guest Posted From: 217.43.52.51 |
It is "magic" then, that so many MK VI/R Type engines have covered colossal mileages on the Brichrome liners? The archival extracts do not bear out the reality of 14 years of production. There are no ridges. See the facts and ignore the speculation. Jeff, the studs are so hard that the Snap on tool would not bite. The iron is too hard to scuff. (Message approved by david_gore) | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 602 Registered: 07-2018 |
I have a 4.5 litre block sitting in my basement now as I type this with 2 last studs that won't budge. The tool doesn't slip, but it was springing the stud so much I didn't want to twist it off. I will try the pipe wrench, I was planning on gently heating the block up in that area with oxy/acetylene, but that is very time consuming and uses much gas. I used 2 pairs of vise grips some 30 years ago when I did my 4.25 litre and thoroughly chewed the crap out of the studs, and I replaced those. I may have even used a pipe wrench, but I can't remember. Keeping in mind that the 4.25 litre block had many studs right into the water jacket that were rusted right in there, where RR fixed the "screw up" on the new block. I would have liked to been a fly on the wall watching the RR mechanics doing a first time decoking service and struggling to get the head off. | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 603 Registered: 07-2018 |
Is that corrosion or pitting in the casting from poor quality alloy, impurities, and/or a bad casting ? From the looks of it, things went wrong due a quality control problem in the pistons them selves. That top ring is very thin compared to modern rings, it would be especially susceptible to failure once those landings started to grow larger. I can even see the gap with my naked eye. I still have my pistons around, I'll take a look and post some photos later. They're in pretty bad shape.  | ||
| ChristopherCarnley Unregistered guest Posted From: 217.43.52.51 |
This is an original R-R piston as supplied by Wellworthy, for the majority of EPW cars. The corrosion pits are part of the ring breakage problem, corrosion worn groves leading to loose brittle rings and their fragmentation. I have had to use the "Barbaric Stillsons" on several cars as the tight studs were fitted in Crewe, when men were men who never listened to fanciful fairy tales. (Message approved by david_gore) | ||
| RayWhite Unregistered guest Posted From: 217.39.199.162 |
So there we have it. Two contradictory arguments from two experts. Meanwhile I am left non the wiser. For what it's worth, I doubt there are reliable records anywhere of how often piston rings needed to be replaced; regardless of how many miles were covered or how hard the driving when these cars were in regular use; so documented evidence in support of either argument is probably non existent. Where I think were do all agree is that leaving a car standing for years without use is as bad if not worse for the engine as thrashing it. . (Message approved by david_gore) | ||
| Jason Watson Experienced User Username: crikeydawn Post Number: 116 Registered: 07-2023 |
"So there we have it. Two contradictory arguments from two experts".....and who would have thought. All I know from observing cars for sale a surprising amount of them have had engine rebuilds and not even seen 100,000 or anywhere near. So something is up. | ||
| RayWhite Unregistered guest Posted From: 217.43.17.131 |
Jason. I think that mileage 'per se' has less to do with engine life than continuous mileage. Many cars have survived by being stored in a garage or barn and not turned a wheel for many years only to be pressed into service without adequate preparation. We have all seen these TV shows where the first thing they do is try to get the engine running. No thought seems to be given to the years of rust build up on the cylinder walls and piston rings which act as an efficient grinding compound when they are forced into action. The drag that is exerted on the piston ring grooves must be considerable and the cylinder bore wear rapid. Cuff liners or not, I am not at all surprised that the rings break up. . (Message approved by david_gore) | ||
| Jason Watson Experienced User Username: crikeydawn Post Number: 117 Registered: 07-2023 |
I should go down and find my pistons from my 4.9. The car was running before flooded, but the pistons indicate not running well. | ||
| RayWhite Unregistered guest Posted From: 217.43.17.131 |
Another engine killer is - as Christopher Carnley has mentioned - is condensation. If you add sulphuric acid from the products of combustion into the mix it can play havoc unseen.  . Even with cars that are used regularly, they often are only used for short journeys and never get warmed up enough. I imagine all those cold starts - especially in colder temperatures - where the choke is used extensively, any protective oil is simply washed away with the unburned petrol. What chance do the poor old things have? (Message approved by david_gore) | ||
| RayWhite Unregistered guest Posted From: 86.131.47.52 |
https://www.kda132.com/technical-problems-with-the-mark-vi/ What are we to make of claims such as these when they are presented by experienced Bentley restorers? I want a Mark 6 that will be capable of sustained 70 mph journeys. I can perhaps handle a rear axle upgrade but I don't want to pay out for an engine rebuild costing perhaps as much as the car is worth. (Message approved by david_gore) | ||
| TimNorth Unregistered guest Posted From: 31.53.146.243 |
Buying a 65-70 year old car must necessarily be a gamble. As far as the engine is concerned there is a risk of over-thinking things. If having carried out all the usual checks (compression, oil pressure, running temperature etc etc) everything appears ok then there is little point in worrying whether the liners are short or long. Even if they had been changed or fitted with them from new an old engine can fail. Accepting that a full flow oil filter is desirable the absence of the same should surely not be a deal breaker if the engine seems ok. s I understand it not all the oil flows through the full flow filters on these engines in any event. If a regime of frequent oil changes is employed and the car is used in a manner approaching the way it was designed to be used-which most are not, sadly, I suspect that a by-pass filter will not increase the chances of a failure to any or any significant degree. To reduce the gambling element there must be incontrovertible proof of the engine having been recently rebuilt to a high standard or you do or have done the same yourself, in which case what length liners are fitted would be academic. (Message approved by david_gore) | ||
| RayWhite Unregistered guest Posted From: 86.131.47.52 |
Thanks for your contribution, Tim. I am not naïve enough to imagine that buying one of these cars would be without any issues. What I am trying to establish, however, is whether or not claims that the short chrome liners being responsible for piston ring failure are true or false. I seem to have hit a nerve. Some experienced people are saying they are a disaster waiting to happen while others are strongly refuting such claims. For my part, I don't mind either way. If a car has not had a documented engine rebuild after all these years then I will not buy it. I would prefer to pay a bit more for a car that has been cared for. If, when an engine rebuild has been carried out, all I am told is that it has been rebored, I would not trust it to last long as these liners are so thin already. Someone hoping to sell their car might have saved on the expense of re - lining the engine... and I don't want to find that out just a few months later.! If the engine has been re lined I would expect full length liners to have been used; wouldn't you? (Message approved by david_gore) | ||
| joeguttridge Unregistered guest Posted From: 82.69.47.200 |
I don't pretend to be an expert here, but the top ring in the photo seems odd. It looks to comprise 2 rings in a single groove, where I would have expected a single 3/32" thick ring. Or are the big bore engines different to the old 3.5" ones. The ring gaps also look a bit loose to me, even allowing for the rings being free in the piston. On another matter, is the excellent Australian technical site down for good (bulletins, w/s manuals etc.)? I haven't been abe to access it over here (UK) for a while now. Or am I just not doing something correctly? (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 4263 Registered: 04-2003 |
Hi Joe, The Australian Technical Library server has been shut down pending possible relocation to another server and a change in Administrator. At this time, I have no information on when this is likely to take place however you can be certain any future information in this regard will be posted in this forum. | ||
| Jeff Martin Frequent User Username: jeff_r_1 Post Number: 629 Registered: 07-2018 |
Joe, here's a quote from the post above where the guy with the tats is using a pipe wrench to remove the studs, it explains what's going on. "He had taken the pistons out due to heavy oil consumption and low compression. All of the top rings were in fragments, the grooves had corroded oversize, so he had the grooves machined and fitted double steel rings to compensate". | ||
| Bill Vatter Experienced User Username: bill_vatter Post Number: 167 Registered: 09-2004 |
The direct cause of broken rings is the ring groove has become overly wide. The rings flex rocking up and down in the groove that allows it because of too much clearance. The top rings break because it is the top groove that wears. Two causes of the excessive wear are possible and have been proposed. corrosion and mechanical wear from friction. Most likely, IMHO, it is a combination of both. Y'all can argue about which factor is the most influential. Both mechanisms are enhanced at the top ring groove. There is more vertical force on the top ring because it is holding almost all of the compression and combustion pressure. Therefore more friction between the ring groove and the ring as the ring moves in and out following the contour of the cylinder, and therefore more mechanical wear. The top ring and groove possibly have more exposure to corrosive combustion gasses, although IMHO, that isn't certain. The top ring and groove will be much hotter than the second ring and groove, and heat usually accelerates corrosion. I agree with those who think the wear step below the bottom of the liner is less of a problem than stated by many. However, it does cause the ring to move in and out rapidly at that place as the ring follows the cylinder. Most certainly the ring will move less in a very straight bore than in a cylinder that has significant taper. It is very reasonable to conclude a straight bore will challenge the rings less than a worn bore. Oil has a lot to do with it. Modern oil is so far superior to what was available in the early postwar years there is really no comparison. Modern oil has anti-wear and corrosion inhibiting additives that weren't there back in the day. All forms of engine degradation, whether it be mechanical wear or corrosion will be greatly reduced compared to what was typically the case back in the day. As evidence, a modern engine can be expected to last 300,000 miles or more, which was unheard of in the early postwar years, even though the materials and design fundamentals of the engine are little changed. If your engine has broken rings, the ring grooves are certainly over-wide and new pistons are needed. To fit new pistons, you will need to rebore the block, and that will produce nice, straight cylinders. IMHO, that reconditioning combined with modern oil will result in the engine running well for well over 100,000 miles, regardless of liners or no liners, which is likely going to be more than any owner today will need. Buying a car today is risky if you don't know the maintenance and overhaul history. However, you can take out a spark plug and look inside with an endoscope. With the piston down in the cylinder, it is possible to see the lower boundary of the short liner, if it is there. Perhaps it has been removed in conjunction with an overhaul. If so that should give you some confidence. The terminal condition of a broken ring is a broken bit of ring chewing its way up into the combustion chamber. That will almost always cause frightful knocking when the broken bit of ring gets caught between the piston top and the cylinder head. However, the car will still run with the second ring holding the pressure, and after a while the knocking will diminish and eventually vanish either from the broken bit of ring being hammered into the cylinder head or piston or or being blown out the exhaust. I have seen engines where broken rings have done all of that in multiple cylinders. If it has happened in an engine and not yet repaired, you can see it with the endoscope. |
