Hi Guys, i was just about to fit my newly bored cylinder, its bored to an NOS piston 60+ with the rings in the cylinder the oil ring end gap is 12 thou but the other 2 are at 20 thou, what do you recommend? getting +40 rings and filing them ?
the piston to cyl gap is 5 thou
email (option): taybrig@shaw.ca
Hi Kevin. Ian has posted the engine clearances in the technical section. But I just checked in the standards book which quotes:- from new 008"-012" acceptable at overhaul 014" and condemned at 030". It seems to me that yours are well past acceptable and on their way to condemned. I would suggest new rings from a source that will not be over gaped. + 40 rings wont work. You'd need to go at least to your +60 size.
Ron
email (option): ronpier@talk21.com
I believe 0.040"oversize rings would be a bad move. While your present gaps are not ideal, it would be OK to fit them. You may have marginally higher oil consumption. Ring gaps given in manuals should be considered a minimum rather than a maxinimum. It is far better to be a few thou over than a few thou under.
email (option): pvlietstra at gmail
Yes, plus .040" rings won't be any good...Regapping rings will work if you were fitting rings the next size up, such as +.040" rings to a +.020" bore..It's an old dodge if the correct rings weren't available...
I was advised it could be done by an 'old boy' back in the early 70's..(and now I'm the 'old boy'..:laughing:)...Ian
email (option): ian@wright52.plus.com
thanks guys, ill order another set of +60 from Draganfly, someone close by me has what he thinks is an NOS cylinder and head for an M20 and is asking 200 quid for them, i dont need them (yet) lol but is that a good deal and what should i look for other than bore size of 82mm
email (option): taybrig@shaw.ca
I bought some +60 rings (for a +60 rebore) from Draganfly a few years ago and the endgap on the compression rings was around 65 thou although the oil ring was OK. A replacement set was the same and I was informed that only the lower limit on the gap was important and a larger gap was OK. :face_with_rolling_eyes:
I got another set from somewhere else that were OK (can’t remember where from though :thinking_face: )
email (option): petercomley@web.de
I got another set from somewhere else that were OK (can’t remember where from though :thinking_face: )
A piston ring seal by allowing the air to get behind the ring and then push it against the bore
If the gap is too big then the air will just pass through it rather than try to squeeze down the side of the ring then under it .
This is why side clearance is so important to a well running engine.
Also rings are precision ground to the bore diameter.
When you fit oversized rings with the gaps filed down the ring does not touch around the full circumference .
When in use it will be forced to conform but the spot where it touches , usually the gap & directly opposite will wear a lot lot lot faster .
SO it is a bodge that is done to get you to work, till the correct size rings are obtained.
If left in too long the rings wear unevenly then either come out of the groove or break, neither of which makes the bore particularly happy.
And for those who think this is my anus talking, get a set of oversized rings, square them in the bore then hold the barrel up to the light and see just how much is touching the barrels .
Do the same with a ring that is the correct size
email (option): bsansw1@tpg.com.au
I agree regarding ring gaps...The tolerances are there for a reason...
As far as fitting filed rings of the next size up it certainly couldn't be argued that it's best practice and should only be regarded as a 'get out of jail card' if the correct rings aren't available...
However, I was told of this 'trick' by a chap who was very well known in motorcycle circles when I went to his shop for some rings for an A7...He didn't have the correct size and looked at me as if I was a young simpleton when I didn't seem to be aware of 'clipping' rings as he called it...
He supplied the 'oversize' rings and I went and fitted them as instructed...Frankly, it worked fine until I stripped the top half of the engine to do some other work around 12 months later.... Theoretically a bad move, I wouldn't argue against that, but it worked. Of course every effort should be made to acquire and fit the correct parts!!....Ian
email (option): ian@wright52.plus.com
In my opinion both Trevor and Ian are correct, different over sizes of rings are different if only because in new condition they aren't "round" in the normal sense however the difference is small and most will happerly bed down if used sympatheticaly. As far as the gap is concerned the ideal ring wouldn't have one but as their temperature varies a gap is required to acommodate the associated expansion. Thus as long as it is big enough to avoid the ends contacting under the hottest conditions thats fine, if it's a bit larger its no big deal as the rings still opperate as a labyrith seal despite the theoretical lost of gas.
Richard.
I don’t see why Trevor decided to reference my post when making his comments.
I would have thought it obvious from the text that I was not in agreement with the claims by Draganfly that what we (and BSA) would consider excessive end gap on a new set of rings was acceptable. I was merely trying to alert the original poster that his reliance on Draganfly for a ring set with the characteristics he was seeking, might be overly optimistic. Particularly as he appears to be in California so postage could be a cost factor to consider.
In my opinion, Draganfly do offer a valuable service but one has to be alert to the occasional differences of opinion.
cheers
Pete
email (option): petercomley@web.de
new rings arrived today from Cox and Turner, and the gaps are 12-13thou so cylinder is now on
so now onto the clutch and gearbox assembling
thanks again guys
email (option): taybrig@shaw.ca