len1 Posted October 6, 2017 Report Share Posted October 6, 2017 Before i start gapping my Grant piston rings i thought i would double check the info i have to hand. tr6 0.020 .....leaflet says gap of 0.003 - 0.004 per inch......my maths says 0.009 - 0.012 anyone care to confirm so i can get some sleep tonight ! thanks Len Quote Link to post Share on other sites
Motorsport Mickey Posted October 6, 2017 Report Share Posted October 6, 2017 Stick 15 thou in there Len, as long as it's not too tight it's not at all critical, no power will be lost or oil burnt or crankcase compression caused. Mick Richards Quote Link to post Share on other sites
RogerH Posted October 6, 2017 Report Share Posted October 6, 2017 (edited) Hi Len, the gap has no need to be precise. 0.020" is fine in my opinion. The compressed air in the top is not there for long enough to squeeze by three small gaps. .leaflet says gap of 0.003 - 0.004 per inch is this per inch diameter or length of ring (circumference.) So at 2" diameter the gap would be 6x 0,04 = 0.024" (not sure what a TR6 bore is but must be more than 2"_ Roger PS - just seen Micks post - go with that. Edited October 6, 2017 by RogerH Quote Link to post Share on other sites
len1 Posted October 6, 2017 Author Report Share Posted October 6, 2017 Thanks Mickey and Roger Roger....leaflet says 0.003 - 0.004 per inch of cylinder diameter .......book says diameter of bore 2.9405 + my bore of 0.020 len Quote Link to post Share on other sites
Guest ntc Posted October 6, 2017 Report Share Posted October 6, 2017 +20 over it needs to be 4 thou. Quote Link to post Share on other sites
len1 Posted October 6, 2017 Author Report Share Posted October 6, 2017 what do you mean Neil Len Quote Link to post Share on other sites
Guest ntc Posted October 6, 2017 Report Share Posted October 6, 2017 You have gone +20 in the block? then the gap is 4 thou Quote Link to post Share on other sites
RobH Posted October 6, 2017 Report Share Posted October 6, 2017 http://www.diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php Quote Link to post Share on other sites
GT6M Posted October 6, 2017 Report Share Posted October 6, 2017 (edited) and wot ye gonna doo with the oil rings / thin ring || spacer 1 this / || / 2 this \ || \ 3 this \ || / 4 this / || \ me self, went for 2, as logik says it,ll scrape better get it wrong, like once did wid Cords, an engine drank oil M Edited October 6, 2017 by GT6M Quote Link to post Share on other sites
len1 Posted October 6, 2017 Author Report Share Posted October 6, 2017 oh .....now its getting complicated ! i will stick with Mickey ......thanks all. the rings i bought are + 0.020 ...so i havent a clue any more ! I am only a joiner cheers Len Quote Link to post Share on other sites
RogerH Posted October 6, 2017 Report Share Posted October 6, 2017 Hi Marcus, can you explain your little drawing of what looks like stick men. Are you saying the flat rings above and below the oil ring are angled !!! Roger Quote Link to post Share on other sites
GT6M Posted October 6, 2017 Report Share Posted October 6, 2017 correct Rodger, recaal me engine build on CT,!! not the rings above oil rings, but the thin oil rings ones that fit onto the oil spacer it stumped me for a while, even the makers did,nt realise it med a difference and could,nt say which way, !!! butt, recaaled the olde Cords rings wer different frae side to side ye bung em on a flat surface an press doon it, either go upwards or doon wards best way t,describe it is like a saucer I put both rings facing doon wards, so t,scrape better M Quote Link to post Share on other sites
RogerH Posted October 6, 2017 Report Share Posted October 6, 2017 Hi Marcus, so that would be (1) in your little list. assuming that moving down is to the right. I will look at that on the next strip down (this winter). Roger Quote Link to post Share on other sites
Waldi Posted October 7, 2017 Report Share Posted October 7, 2017 Hi Marcus, I guess it is my lack of english (I hope????), but think I'm about to learn something from you. Can you explain a bit more about the angled rings please? I do not understand. Thanks, Waldi Quote Link to post Share on other sites
RogerH Posted October 7, 2017 Report Share Posted October 7, 2017 Hi Waldi, I think Marcus is saying that the top and bottom flat rings that go either side of the shaped oil ring have a dish shape to them (they are not flat) So position them as if the dish was upside down - the rim of the dish pointing towards the sump - as in image 1 of his post. I can see how this would work but have never seen it before. Roger Quote Link to post Share on other sites
Waldi Posted October 7, 2017 Report Share Posted October 7, 2017 Thanks Roger (and Marcus), I did not know they are "cupped". Regards, Waldi Quote Link to post Share on other sites
len1 Posted October 7, 2017 Author Report Share Posted October 7, 2017 I have had a good look at the thin rings that go either side of the oil ring and have to say the Grant ones I have are flat..and that's with my glasses on... Len Quote Link to post Share on other sites
GT6M Posted October 7, 2017 Report Share Posted October 7, 2017 (edited) Len , put the rings ona flat surface, an press doonwards wid yer finger if it dont move, turn it over, an press Rodger, its No 2 , as both ar pointing down the bore this,ll mebe help folk see it better,!!! https://www.google.co.uk/search?q=cords+piston+rings&client=firefox-b&dcr=0&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiamvzT3N7WAhVLahoKHenNBKcQ_AUIDCgD&biw=1055&bih=622&dpr=1.62#imgrc=6JPOTmef8DOwcM: the grants rings I got deffo had a tilt whenst pressed doon butt, nee where near as cupped as a Cord was, { still is } M Edited October 7, 2017 by GT6M Quote Link to post Share on other sites
RogerH Posted October 7, 2017 Report Share Posted October 7, 2017 Hi Marcus, my bore was pointing the other way Roger Quote Link to post Share on other sites
Waldi Posted October 7, 2017 Report Share Posted October 7, 2017 Thanks Marcus, I see the Cord rings date back a "little" in time....1940. Interestingly I suddenly realize a variation of that design is still used for large reciprocating compressors in industry for stuffingboxes (to seal the piston rods). Regards, Waldi Quote Link to post Share on other sites
len1 Posted October 7, 2017 Author Report Share Posted October 7, 2017 Thanks Marcus. Unfortunately my pistons are in now...next time Cheers Len Quote Link to post Share on other sites
lee Posted October 16, 2017 Report Share Posted October 16, 2017 Reading with interest as this is one of my next jobs. Quote Link to post Share on other sites
Peter Cobbold Posted October 16, 2017 Report Share Posted October 16, 2017 The ring gaps on supercharged engines should be increased over standard - they can get hotter and expand more. I think one TR6 owner has experienced pistons failing....and photos to show. Peter Quote Link to post Share on other sites
Waldi Posted April 13, 2018 Report Share Posted April 13, 2018 and wot ye gonna doo with the oil rings / thin ring || spacer 1 this / || / 2 this \ || \ 3 this \ || / 4 this / || \ me self, went for 2, as logik says it,ll scrape better get it wrong, like once did wid Cords, an engine drank oil M Just some more experience to share: I bought a new set of piston rings from Grant. They came with clear instructions, the compression rings all marked "TOP". The thin oil rings (called oil rails in the instruction) were cupped, as indicated earlier by Marcus. The "worst"ones had up to 2.5 mm lift (on the opposite side, when pushed down on one side on a flat hard surface. So I called Grant-USA, and was immediately connected to an engineer. He said that they should not be cupped, and was honest enough to apologize and indicated this was probably due to a worn tooling issue. I do appreciate when companies are honest like this. He offered to send me a new set of oil rails, free of charge, which I received in 1 week; excellent service! I checked the new ones, and these were also cupped a bit, but the "worst" still less than 1.5 mm. So some cupping is acceptable, and I feel my 2nd set is ok. Now it is just a matter of finding the best method to fit. So I asked the Grant engineer again, and he answered as follows: "No real order, but I might try putting the cup up on the bottom and down on the top. Does that make sense. See how they rotate. You should be good". I drafted this idea in below picture on the right side of the piston (I think) I'm not sure what that method will do/how it works, clearly dynamic behaviour of oil rings in combustion engines is out of my league... During movement, the cupping (angle) will be increased in one direction, and reduced in the other direction due to the friction, but this effect may be marginal. I drafted a schematic view, see below. If I understand corrrectly, I think Marcus recommends to install both rings with the cup "facing down", so both rings as the bottom ring in the left hand side of the pic. I think I will go with that, you can't beat experience when in doubt. If somebody has other idea's, I'm interesed to hear. Regards, Waldi Quote Link to post Share on other sites
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