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30 September 2015 at 8:04 am #51973Steve LordMember
Things don’t always go to plan where our cars are concerned, do they – just as in the rest of life. Looking back over my posts on this site, there are many which tell of successful mods I’ve made to my MS. Well I don’t always get it right so I think I ought to recount failures as well, when they occur. I have fitted a Mercedes engine in my car, taken from a 1959 Fintail saloon. It’s a type I’m familiar with & I’ve made a lot of alterations to it to make it more economical so I can afford to run my car as a full-time daily-driver – which I have done, for the past 2 years. But because I’ve forced the economy-efforts too far, my car now sits in the garage with its cylinder-head removed, while I await the arrival of rare & costly spare parts from Germany.
Problems began last week with a rhythmical misfire at idle, telling of a leaking exhaust valve which was confirmed by a compression test. I removed the cylinder-head & was dismayed to find severe wear in 3 of the 6 exhaust-valve guides, that were brand-new in this head only 20k miles ago. The leaking exhaust valve came from a cylinder whose guide wasn’t worn, suggesting there are at least two un-related causes of the faults. All the exhaust-valves were found to have pits in their faces, some worse than others & the pitting was the cause of the initial leakage, which would have gone on to full-scale burn-out had I continued to use the car.
I am guilty of not practising what I preach, in that I’d used cheap cast-iron valve guides which cost £6.50 each instead of the genuine Merc phosphor-bronze ones which then were about £57 each. As I’d had to considerably de-rate my engine to enable the rest of the MS to reliably cope with it, I felt I had a sporting chance of getting away with this economy. Bad call.
I have now ordered the real deal, along with 6off new sodium-cooled valves to run inside ’em. The pitting is likely to have been caused by my running the engine with its ignition-timing over-advanced & with an excessively-weak mixture, as these tweaks used in conjunction with modern gas can produce big gains in fuel economy in some old-fashioned engines. Just not big enough to swallow up the cost of new guides, valves & associated parts every couple of years – a solemn warning!
Steve Lord
30 September 2015 at 8:48 am #54329Patrick CarrollParticipantOh dear – sorry to hear about that Steve – false economy indeed I’m afraid. Looks like your engine swap just changed one type of exhaust valve failure for another!
Good luck with the repairs & improvements – look forward to hearing that it’s back on the road very soon.
Pat
30 September 2015 at 1:57 pm #54330Steve LordMemberYou’re dead right Pat, I can assure you the irony is not lost on me. Regarding time to finish the repairs & get the car going again, in the first instance it’s in the hands of my parts suppliers. Steve
22 November 2015 at 8:56 pm #54331Steve LordMemberWell all is now fully sorted; the car was back together & running before the NEC show in fact, but I forgot I’d left this thread hanging unfinished. My grateful thanks go to club-member Terry Handley for his splendid first-hand product knowledge of my car’s 1950s Mercedes engine & its limitations. His willingness to share this in detail with me in many emails must have taken great chunks of his time. Cheers mate, I owe you.
Steve Lord
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