How important to check ring gap

Discussion in 'Mech Tech' started by jmarchant1970, Jan 9, 2020.

  1. Hello again

    I have now finished building up my 16oo tp long block. Hooray!
    Loads of new bits including new AA pistons and barrels.
    Now having re-read a few engine build threads I now realise that I didn't check the ring gaps.
    I realise the implications of them being too tight, however as a fairly good quality parts supplier, would AA really send out a set of pistons (with rings already fitted), and barrels that were already out of tolerance?
    I hope not as I really don't want to strip the whole thing apart again. : (
    Has anyone ever had to adjust the gaps on this product or is everything always good?

    Cheers

    John
     
  2. It’s something I would lose sleep over. The gap is too tight you’ll crack the ring and destroy the engine. To loose . You get blowby I’ve always had to file rings on my Harley Davidson’s. But I am always. Using a bored out cylinder..and the pistons must be Matched to each cylinder. And you have four. Were they numbered? Marked with a pen ,corresponding 1 to four.?. Usually the Pistons are matched to the cylinders. But when you add the rings. You must check the gap.. I hope someone here proves me wrong. But if not. Open it up and star5 over....sorry
     
    Last edited: Jan 9, 2020
  3. Just checked my AA piston rings and all apart from 1 which was a tight tolerance were pretty much spot on what AA recomended. But they were fitted into my own pots so could have been my cylinder was tight.

    There's a few other AA sets on here sure they'll comment soon.



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    jmarchant1970 likes this.
  4. No not numbered, but the piston, rings and barrels come ready fitted
     
  5. Call them up!, I’m sure you know the questions but you’re asking the wrong people for the answer, I would be very nervous to put any engine in the world together without knowing the gap tolerances on the piston rings as they are in the bore, it’s engine building 101
     
    Last edited: Jan 9, 2020
    Iain McAvoy and 77 Westy like this.
  6. I contacted AA via their website contact form they replied overnight..

    Jonathan at aapistons was very helpfull

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  7. 77 Westy

    77 Westy Supporter

    Yes. AA quality is unreliable, they might be okay, they might not – are you feeling lucky? Send a message so you have their answer in writing, but even if they say it’s correct, I’d still take it apart.

    Never assume any new part is correct and checking the ring end gap and side clearance is an essential step in building an engine.
     
    Last edited: Jan 9, 2020
  8. Yeah, I emailed them this morning so fingers crossed
     
  9. 77 Westy

    77 Westy Supporter

    Please tell us what they say.
     
  10. Will do


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  11. I've just asked about their ring side clearance spec too as they're a lot tighter than stock... down at the 0.03/0.04mm end! Or 0.0015" in old money

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  12. So here is there response :-

    Hello John

    The gaps are done but you did pull the pistons out and clocked them right?


    Jonathan

    AA Performance Products
    —————————————————————

    I assume by “clocking” he means setting the position of the ring gaps at 10pm, 12, and 2pm?

    John


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  13. I would say he does mean positioning the ring gaps in a staggered arrangement.
    Don’t know if “the ring gaps are done “ sounds positive or not. What will they say when you email them to say its nipped up?
     
    jmarchant1970 likes this.
  14. JamesLey

    JamesLey Sponsor

    I'd just do them for peace of mind. What's an extra day or two given you've gone to the trouble of building an engine?
     
  15. 77 Westy

    77 Westy Supporter

    Side clearance is typically 0.001”- 0.003”, I’d be happy with 0.0015". And I’m certain AA will be too.:)
     
    Deefer66 likes this.
  16. 77 Westy

    77 Westy Supporter

    He does. Did you?
    The exact position isn’t important, they rotate when the engine is running, but the gaps shouldn’t be adjacent to each other.
     
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  17. Yeah I did that.
    How I didn’t think to check the gaps is beyond me


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  18. 77 Westy

    77 Westy Supporter

    AA says it’s okay, and the chances are it will be fine but I’d take it apart for peace of mind - I wouldn’t like to run an engine with my fingers crossed.

    Are the AA pistons marked for direction?
     
    dubsurftones likes this.
  19. 77 Westy

    77 Westy Supporter

    Incidentally, what the gap should be varies from one ring manufacturer to another and one piston manufacturer to another and one engine builder to another.

    Something to consider when you decide what is correct – if it’s too small the ring could seize in the bore and tear the top off the piston, if it’s too big they’ll be some blow by and loss of efficiency, but the engine won’t be damaged.

    For what it’s worth on the 2316cc Type 4 I used 0.0075” per inch for the top ring with KB Hypereutectic pistons and Hasting rings.
    Piston ring installation.jpg Piston ring gaps KB Hypereutectic.jpg
     
  20. Looked all over for that side clearance !

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