Method failure

Homepage Forums Technical issues Engine Method failure

Viewing 4 posts - 1 through 4 (of 4 total)
  • Author
    Posts
  • #51973
    Steve Lord
    Member

    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

    #54329
    Patrick Carroll
    Participant

    Oh 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

    #54330
    Steve Lord
    Member

    You’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

    #54331
    Steve Lord
    Member

    Well 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

Viewing 4 posts - 1 through 4 (of 4 total)
  • You must be logged in to reply to this topic.