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Thread: R500 Duratec valve spring failure

  1. #11
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    Sep 2020
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    Thanks guys, my plan is to take the engine to them; I’m sure they will have a clearer picture of the spec when they have it apart. In fairness it was a quick telephone call after 5pm on a Friday

    Thanks for the info on the cams & springs John; not sure what work I’ll have done, I’ll be lead by the engine builder.

    Croc, thanks for following up, always good to get other opinions.

  2. #12
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    If it helps, in the UK there have been several failures of valve springs (usually with fairly catastrophic consequences) in 'early' R500D engines. These seem to have been the single parallel Kent springs - they were fine at the very start of R500 builds but later became unreliable.

    As a consequence, Caterham Cars moved to a Cosworth conical spring and standard cap set-up (around 2010/11, so it sounds as though your engine might be one of the last pre-Cosworth spring ones), and this remains the current build spec for all of Caterham's performance engines - so 420 and up, including all 620s (which, whilst lower revving, are subject to a hard duty cycle).

    The recommendation from Mic Attree (well known as Caterham's main man when it comes to the build of these engines) is to replace the Kent springs with Cosworth conical springs and standard caps. He is not aware of any failures with the Cosworth springs.

    Sorry that I don't have part numbers to hand!

    James

  3. #13
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    I wish I had heard of this issue prior to my rebuild. Neither Raceline nor Kent mentioned it and Kent does sell double spring kits for their cams more extreme than the DTEC35. Were the failures on track day cars that spent a lot of time north of 8000rpm, or did the issue also affect street cars that just saw brief forays to high revs in the lower gears?

    Thanks,
    John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  4. #14
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    John - I'm not an expert on this but valve spring failures on early R500D's are pretty well known, at least here in the UK. From what I know there is a mix of usage cases, ranging from people who do very little track-time through to others where trackdays are a common occurrence.

    I think there have also been issues with the double spring arrangements, too - though disaster can be prevented in the event of the main spring failing by the second spring that saves the day. But then you have to realise that something is amiss as the surviving second spring can mask the primary failure. I will look out what I can, but I think the flaw in the two-spring set-up is due to interference between the two springs. I can vouch for this being an issue as I have personally witnessed the strip-down of an engine where a second spring had failed (this followed an earlier failure of a single spring, requiring a major rebuild that included fitment of the double springs - doohhh).

    If you search BlatChat (likely in TechTalk) and/or the main Facebook Groups you will pick up this stuff quite easily.

    James

  5. #15
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    Quote Originally Posted by Shortshift View Post
    The recommendation from Mic Attree (well known as Caterham's main man when it comes to the build of these engines) is to replace the Kent springs with Cosworth conical springs and standard caps. He is not aware of any failures with the Cosworth springs.
    Hi James - Did Mic write anything up on the topic so as to read more? Would be interested to study in more depth. Thanks Mike
    Mike
    2021 Caterham CSR "CatKong"
    2010 Caterham CSR with Cosworth 2.3 Duratec
    2018 Caterham 420R with 2L Duratec 210hp at Donington UK
    1975 BMW CSL Group 4 (restoration finished - track set up time)
    1977 Holden Torana "A9X" (awaiting restoration)
    1985 Holden Commodore SS Group A (suspension restoration)
    1985 Holden Commodore Group A (suspension set up)
    1982 Ferrari 400i (radiator replacement)
    1965 Ford Mustang Fastback "Holman Moody"
    1992 Ford Escort RS Cosworth WRC (dyno time)
    1990 Range Rover 2 door Classic


  6. #16
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    May 2020
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    Mike - I was carrying out my own research into this and, as part of that, I reached out to Mic. He replied with some background and a touch more detail and I have published (above) as much of what he told me as I think is right to reproduce in a private forum without his express permission. But I've no problem in sharing his note on a private basis so I'll send that to you as a pm (actually, it really adds very little to what I've said).

    James

  7. #17
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    Thank you James!
    Mike
    2021 Caterham CSR "CatKong"
    2010 Caterham CSR with Cosworth 2.3 Duratec
    2018 Caterham 420R with 2L Duratec 210hp at Donington UK
    1975 BMW CSL Group 4 (restoration finished - track set up time)
    1977 Holden Torana "A9X" (awaiting restoration)
    1985 Holden Commodore SS Group A (suspension restoration)
    1985 Holden Commodore Group A (suspension set up)
    1982 Ferrari 400i (radiator replacement)
    1965 Ford Mustang Fastback "Holman Moody"
    1992 Ford Escort RS Cosworth WRC (dyno time)
    1990 Range Rover 2 door Classic


  8. #18
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    James, would you mind sharing with me too, please? I just completed a long, somewhat painful, 2.0L build using Kent DTEC20 cams which are halfway between the DTEC10 in the R400/420 and the DTEC35 in the R500. Based on other input, I reused the Kent single coil springs from my prior build (Kent DTEC10), which are apparently the old R500 springs prone to failure, so I'm, um...concerned.

    Thanks,
    John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

  9. #19
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    May 2020
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    John - no worries. PM sent.

    James

  10. #20
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    Krtypton: The Belmont NC tuner is a member of this forum and goes by 1TurboFocus here. He is known as TurboTom on the Focus Forums. He is a long time Zetec builder and tuner and is also very involved in Duratecs. Since your engine is so rare, I doubt that he knows of it or its spec.
    Kitcat:AKA, Sir Spinsalot
    '97 Caterham Super Sprint, 1700 Crossflow-sold
    '09 Birkin S3, Duratec-sold
    '03 Caterham Zetec track car
    '19 Honda Type R, sold
    '19 Miata Clubsport

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