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First time filing piston rings, need advice #715721 11/19/17 2:47 am
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Mark Z Online Sleepy OP
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Doing an upper-engine job on a TR5T, and measuring four of the new Hastings rings, I'm finding that the end gaps are .006", so I assume I will have to file them.

As the title indicates, I've never filed rings before, so I'm wondering exactly what sort of file to use. Also, any tips on clamping or filing techniques would be appreciated.

And, what about grinding with a Dremel tool instead of filing? This would seem less likely to leave burrs, and would not require tight clamping.




Mark Z

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Re: First time filing piston rings, need advice [Re: Mark Z] #715725 11/19/17 3:11 am
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Yes, that makes perfect sense, thanks. I don't think I have any really fine files, so I'll probably have to buy one. Anything in particular to look for, like double or triple-cut?

What's a good gap to shoot for?



Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: First time filing piston rings, need advice [Re: Mark Z] #715735 11/19/17 8:08 am
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Ring gapping tools are available eg eBay $44. Filing by hand makes it very easy to remove too much material and difficult to maintain square ends due to the very small surface area. I always refer to manufacturers specs. sheet that comes with rings regarding ring gap, same with piston to bore clearance.

Last edited by Simon Ratcliff; 11/19/17 8:10 am.

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Re: First time filing piston rings, need advice [Re: Mark Z] #715739 11/19/17 9:45 am
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Stop and think why the gap is small. If the cylinder has been bored to less than the recommended skirt clearance (at least 3 thou at bottom of skirt for late Unit 500, I think), then your engine will seize.

Don't panic if you file a bit bit more off the ring than you meant to. It'll still be fine.

Rings can be easily distorted, affecting their sealing effect.

For better ring sealing in use, make the second ring gap 30% bigger than the top ring gap.



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Re: First time filing piston rings, need advice [Re: triton thrasher] #715751 11/19/17 12:47 pm
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Originally Posted by triton thrasher


Don't panic if you file a bit bit more off the ring than you meant to. It'll still be fine.

For better ring sealing in use, make the second ring gap 30% bigger than the top ring gap.



Ring gaps are there to allow for expansion when hot but leave minimum clearance between the ends of the rings thus providing optimum sealing. Therefore stick to the manufacturers recommendations.

Ditto your tip re 30% bigger gap for the second compression ring - bigger gap means increased blow-by and subsequent loss of power. It also contradicts ring manufacturers specifications.

P.s Google Hastings piston rings tech for relevant info.

Last edited by Simon Ratcliff; 11/19/17 1:05 pm.

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Re: First time filing piston rings, need advice [Re: Simon Ratcliff] #715754 11/19/17 1:04 pm
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Originally Posted by Simon Ratcliff
Originally Posted by triton thrasher


Don't panic if you file a bit bit more off the ring than you meant to. It'll still be fine.

For better ring sealing in use, make the second ring gap 30% bigger than the top ring gap.



Ring gaps are there to allow for expansion when hot but leave minimum clearance between the ends of the rings thus providing optimum sealing. Therefore stick to the manufacturers recommendations.

Ditto your tip re 30% bigger gap for the second compression ring - bigger gap means increased blow-by and subsequent loss of power. It also contradicts ring manufacturers specifications.


Don't dish out bad advice.

You are quoting old manuals that have been shown to be wrong. About 40 years ago in the case of your first erroneous point.


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Re: First time filing piston rings, need advice [Re: triton thrasher] #715755 11/19/17 1:21 pm
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Originally Posted by triton thrasher


Don't dish out bad advice.

You are quoting old manuals that have been shown to be wrong. About 40 years ago in the case of your first erroneous point.


I haven't stated any points of reference. Info actually comes from people who manufacture piston rings: www.totalseal.com. www.hastingspistonrings.com and www.cppistons.com

Last edited by Simon Ratcliff; 11/19/17 1:23 pm.

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Re: First time filing piston rings, need advice [Re: Mark Z] #715758 11/19/17 1:52 pm
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From your links:

Hastings appear to stick to the old factory advice on maximum gap, which is misleading when someone finds that new rings in new bores have an 18 thou gap. The gap can be much bigger without affecting running.

Hastings may have a mind to possible causes of big ring gaps, such as worn bores, which can certainly affect running and could show replacement rings in a bad light. Carillo may have similar thinking, but I can't read their mind.

Total Seal's product appears to have no gap at all, so may not be awfully relevant.

Did you read the bit in your link where Carillo recommend bigger gap on 2nd ring than 1st ring?



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Re: First time filing piston rings, need advice [Re: Mark Z] #715762 11/19/17 2:11 pm
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I didn't invent this stuff, though I've worked to it, with good results.


Originally Posted by Pete Russell
Don't use less than the minimum on the top ring (0.010").It hardly matters if it's bigger,even up to 0.060",but try for 0.010".
Current thinking is to use a 30% bigger gap on the 2nd ring,about 0.003"-0.004" bigger if the top ring is 0.010".
Oil rings aren't critical,and 0.040" would be OK.I'd make it the same gap as the 2nd ring.

Bigger gap on the lower rings helps the top ring to seal,and reduces oil consumption.http://www.speedwake.com/forums/arch...p/t-34413.html
Please read that link,if you want to build good engines.There is a good (and reasonably long) post by Barry R,near the bottom of the page.


Originally Posted by indirect report on AE (Hepolite) tests
http://www.diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php
Even worse is the preoccupation with the size of the ring gap. Yes, there is a minimum but this varies considerably depending on the material used. Normally 0.003"/0.004" per inch of bore size is given but where, for example, low expansion SG (spheroidal graphite) iron is used, it can be considerably less.

It’s no problem if the gap is too small because it can, in the final analysis, be filed bigger but what do you do if it's too big? You cannot stick a bit extra in there!

Well, the answer to that was that you melted them down and started afresh – until AE research asked the question, "What is too big?" and set out to quantify that. The results were interesting – very interesting – and what you are about to read was kept quiet because it bestowed an enormous commercial advantage on AE. This is probably the first time the information has been published although the research was undertaken in the late 1970's – almost 25 years ago.

A Ford Kent engine was stripped and fitted with compression rings which had end gaps of 0.015" when fitted in the bores. The engine was wired up with the usual telemetry to measure blow-by and oil consumption and then run in one of the test cells. After making due note of the blow-by and oil consumption, the engine was stripped and fitted with new compression rings with gaps of 0.025" and the test cycle repeated.

These rings were subsequently replaced by ones having end gaps of 0.035" and the test cycle repeated again. It had been planned to stop at 0.035" gaps ----------> but the results were so interesting that it was agreed to proceed to 0.045” and then not to 0.0055” but to 0.0625” – 1/16"!

Whoever heard of rings with 1/16” gaps – a ridiculous figure – but the interesting thing was that the increase in blow-by and oil consumption at 0.0625” was only marginally above the figures obtained with 0.015” gaps.

Practical tests established that the gap was not the villain of the peace. To all practical purposes the size of the gap didn’t matter. It is important to stress at this point that we were dealing with compression rings that were brand new when fitted to the test engine.


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Re: First time filing piston rings, need advice [Re: Mark Z] #715797 11/19/17 5:36 pm
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I go for manufacturers specifications over a forum posting every time. They're the ones that have done the research and development. Total seal make conventional as well as 'gapless' rings. All the info is there, you just need to read it.


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Re: First time filing piston rings, need advice [Re: Simon Ratcliff] #715801 11/19/17 5:59 pm
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Originally Posted by Simon Ratcliff
I go for manufacturers specifications over a forum posting every time.


I think you now know there's more behind it than just a posting by some nonentity like me. To ignore what you read today would be very stubborn, not that it's any skin off my nose.

Quote
They're the ones that have done the research and development.


Yes they are and like AE/Hepolite in their day, they don't tell everybody everything about their research and development.


Quote
Total seal make conventional as well as 'gapless' rings. All the info is there, you just need to read it.


I gave up looking for it in your link, but I've read the stuff you've recited here, fifty years ago.


I gave the OP two little tips: (1) don't fret if you go over max spec gap; and (2) open up the 2nd ring gap wider than the 1st. They are good tips and you have been a bloody nuisance about it, just because it's new to you.


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Re: First time filing piston rings, need advice [Re: triton thrasher] #715805 11/19/17 6:14 pm
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Originally Posted by triton thrasher

I gave the OP two little tips: (1) don't fret if you go over max spec gap; and (2) open up the 2nd ring gap wider than the 1st. They are good tips and you have been a bloody nuisance about it, just because it's new to you.


Your 'tips' are not only new to me they're apparently new to at least three current piston ring manufacturers.


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Re: First time filing piston rings, need advice [Re: Simon Ratcliff] #715806 11/19/17 6:33 pm
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Originally Posted by Simon Ratcliff

they're apparently new to at least three current piston ring manufacturers.


Don't you believe it!


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Re: First time filing piston rings, need advice [Re: triton thrasher] #715809 11/19/17 6:42 pm
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Originally Posted by triton thrasher
Stop and think why the gap is small. If the cylinder has been bored to less than the recommended skirt clearance (at least 3 thou at bottom of skirt for late Unit 500, I think), then your engine will seize.

Don't panic if you file a bit bit more off the ring than you meant to. It'll still be fine.

Rings can be easily distorted, affecting their sealing effect.

For better ring sealing in use, make the second ring gap 30% bigger than the top ring gap.



Bores were professionally bored and honed to provide .004" clearance to +.020" pistons. (Off subject a bit, you may remember a while back I posted pictures of MY honing job, which was accurately described as "pathetic". After that I took the barrel and pistons to a competent machinist. Fortunately, when I brought it in, the piston clearance was only .0025-.003", so he was able to clean up my bad honing job, get everything nice and round, and properly coarse-hone, leaving .004" clearance).

I'll read Hastings' documentation on the subject and take your recommendations under advisement.

Using NickL's prescribed filing technique, it seems that I should be able to get the ends square, so I'm not inclined to purchase a $40 gapping tool at this time.



Mark Z

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Re: First time filing piston rings, need advice [Re: Mark Z] #715815 11/19/17 6:52 pm
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Originally Posted by Mark Z
Originally Posted by triton thrasher
Stop and think why the gap is small. If the cylinder has been bored to less than the recommended skirt clearance (at least 3 thou at bottom of skirt for late Unit 500, I think), then your engine will seize.

Don't panic if you file a bit bit more off the ring than you meant to. It'll still be fine.

Rings can be easily distorted, affecting their sealing effect.

For better ring sealing in use, make the second ring gap 30% bigger than the top ring gap.



Bores were professionally bored and honed to provide .004" clearance to +.020" pistons. (Off subject a bit, you may remember a while back I posted pictures of MY honing job, which was accurately described as "pathetic". After that I took the barrel and pistons to a competent machinist. Fortunately, when I brought it in, the piston clearance was only .0025-.003", so he was able to clean up my bad honing job, get everything nice and round, and properly coarse-hone, leaving .004" clearance).

I'll read Hastings' documentation on the subject and take your recommendations under advisement.

Using NickL's prescribed filing technique, it seems that I should be able to get the ends square, so I'm not inclined to purchase a $40 gapping tool at this time.



Well, you've got more than one opinion to consider, now.

There are recent(ish) ring seating recommendations too.


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Re: First time filing piston rings, need advice [Re: Mark Z] #715818 11/19/17 7:37 pm
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I was working at the AE R&D Center when the tests referred to above were carried out.
In fact I was sharing an office with the engineer who was the project manager for the project.
I can confirm that no discernible increase in blow by or decrease in power was measurable for ring gaps of between the specified amount and .100-.125".
So, Mark--just file the ends carefully and square, make sure that there are no burrs and make sure that you have ring end gaps of well above the minimum specified.
Within reason--do not be worried if you file off a bit too much.
HTH

Re: First time filing piston rings, need advice [Re: Mark Z] #715828 11/19/17 8:25 pm
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This forum has (and has had in the past) some impressive resources of knowledge and experience.


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Re: First time filing piston rings, need advice [Re: Mark Z] #715863 11/20/17 12:57 am
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I happened to be near Harbor Freight today, so I wandered in and picked up a 12-piece set of needle files, for $2.99! (If I had known they were that cheap, I would have had a set a long time ago.)

I'm thinking, if I use a thin, flat, double-sided file, clamped in a vise, and file both ends of the ring at the same time, making sure to hold the ring perpendicular to the file, the ends should come out about as square as can be. And yes, I'll be sure to dress off any burrs.

I haven't yet read the factory documentation, but it sounds like I have a wide margin of error. Interesting, my Chilton book for BSA, published back in the early '70s, specified a maximum end gap of .008" for A65s, which have a bigger bore than this TR5T. Unless I see something to the contrary, it sounds like I'll be fine with anything from .010 to .015.

As far as seating goes, all I can say is, I've read John Healy's dissertations on the subject multiple times, and I employed the prescribed procedures on the last rebuild of my A65, with great success.


Mark Z

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Re: First time filing piston rings, need advice [Re: Mark Z] #715874 11/20/17 2:26 am
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I've used a flat miniature mill bastard Nicholson while securing the ring in a nylon jawed Panavise .
Go slowly, check fit in the bore frequently.

On the last few top ends I've stroked the piston with rings thru the bores slowly by hand to "prehone"..
Up and down, just enough to feel (and see) it all gliding smoothly through the bore. Worked out well for me.

Don in Nipomo

Re: First time filing piston rings, need advice [Re: Mark Z] #715882 11/20/17 6:16 am
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My point regarding going by the ring manufacturers specifications is that they're based on the rings being produced today and not when your engine was made. The CP pistons site also contains info on boring and honing, the bore needs to be no more than 0.0002" out of round and the surface finish after honing is such that bedding in of the rings to the bore takes seconds - not hours.

P.S An additional $40 on top of the engine build cost is money well spent to ensure the rings are gapped accurately in my opinion.

Last edited by Simon Ratcliff; 11/20/17 6:19 am.

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Re: First time filing piston rings, need advice [Re: Mark Z] #715883 11/20/17 6:29 am
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Originally Posted by Mark Z
I happened to be near Harbor Freight today, so I wandered in and picked up a 12-piece set of needle files, for $2.99! (If I had known they were that cheap, I would have had a set a long time ago.)

I'm thinking, if I use a thin, flat, double-sided file, clamped in a vise, and file both ends of the ring at the same time, making sure to hold the ring perpendicular to the file, the ends should come out about as square as can be. And yes, I'll be sure to dress off any burrs.

I haven't yet read the factory documentation, but it sounds like I have a wide margin of error. Interesting, my Chilton book for BSA, published back in the early '70s, specified a maximum end gap of .008" for A65s, which have a bigger bore than this TR5T. Unless I see something to the contrary, it sounds like I'll be fine with anything from .010 to .015.

As far as seating goes, all I can say is, I've read John Healy's dissertations on the subject multiple times, and I employed the prescribed procedures on the last rebuild of my A65, with great success.


8 thou on an A65 sounds more like a rather tight minimum gap than a maximum.


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Re: First time filing piston rings, need advice [Re: Simon Ratcliff] #715884 11/20/17 6:32 am
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Originally Posted by Simon Ratcliff
the bore needs to be no more than 0.0002" out of round


On a 1970s Triumph?


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Re: First time filing piston rings, need advice [Re: Mark Z] #715886 11/20/17 7:38 am
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Ref. Tt's and NickL's comments. For a competent/professional machine shop boring a cylinder to within 0.0002" of round is not a problem - the problem is finding a competent/professional machine shop. I ended up buying a Mercer bore gauge (graduations of 0.002mm) to check the accuracy of a suspect cylinder. I eventually found a competent machinist who could bore and hone to within these limits.

I recently worked on a 1979 T140D Bonneville with a genuine 4,500 miles on the clock. The bores were standard diameter and the out of round was within 0.0002". With the correct surface finish this allows the rings to seat very quickly and in addition ring to bore blow by is down to 5%. This results in more power, torque and oil consumption down to 2,000 miles/pint. A simple indication of engine condition is to wipe a finger inside the exhaust tail pipe. Does it come out clean or covered in sticky soot.


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Re: First time filing piston rings, need advice [Re: Mark Z] #715983 11/21/17 12:02 am
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Plus 1 for Nickl

Simon there is a very good reason the aftermarket does not supply .010" oversize pistons for most of the popular British cylinders. In only rare situations will the bore clean up at .010". Rarely is the bore at right angles to the base and you have to go to .020" just to get it trued up. Of course this assumes for this to be an improvement the crankcase mouth needs to be parallel with the center line of the crankshaft.

Even taking light cuts using a Kwickway bar, with a sharp tool most of these air cooled cylinders will not come of the bar to a .0002" tolerance from top to bottom. And if it does, and you come back in a couple of days, often it will have changed.

Stress in the casting built up during the heating and cooling cycles get released when you remove the surface tension. Then the vary thickness of the casting below and just above the cylinder base is quite thin and offers little resistance to the pressure of the tool. Above and below the base the tool takes a lighter cut, where the base is rigid and takes a heavier cut. If you are not paying close attention to your work it is very easy to be working to a .002, rather than a .0002", tolerance. The same can happen when you are doing finish honing.

Triumph did the right thing to the T140 when they installed the center 5/16" head studs. They installed them with the long thread and "tit" into the cylinder. When it came to doing the 4 inside 3/8" studs they put them in with the short end down. When they tightened them into the cylinder, the end of the stud's threads bottomed out and distorted the cylinder bore. At least in the end BSA got it right on the A65.

A modern engine is designed so that it is round to .0002" when it is at operating temperatures. All of the water ports are flowed specifically to insure the cylinder stays round to the .0002" tolerance at operating temperatures. Any measurements I have taken on a warm old British cylinder bored to +- .0002" is anything but round and true once the engine warms up. Torquing plates or not. An air cooled cylinder, where the front is receiving a flow of cool air and the back is getting none or more accurately the heated air from the front, isn't conducive to holding a .0002" tolerance!


Re: First time filing piston rings, need advice [Re: Mark Z] #716022 11/21/17 7:35 am
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Any competent machinist with the appropriate knowledge and machine tools fit for purpose should have no problem boring and honing to within 0.0002" of round. I was surprised how many machinists appeared confused when I questioned what limits they worked to and I was equally surprised how many admitted they didn't even bother to check for cylinder roundness after boring and honing. I spoke to about 6 machine shops within a radius of 30 miles before finding Bradbury Automotive Engineers www.bradbury-engineers.co.uk

I'm aware that any air cooled cylinder will be subject to distortion but the further out of round a cylinder is after boring and honing then the greater the amount of wear that has to take place before the rings can provide an acceptable seal - in many cases they never do going by the layer of oily soot inside the average classics exhaust tail pipe/s.

Many people are not aware that there is more than just piston to bore clearance to consider when cylinders go in for a rebore. Out of round tolerances are as important as is appropriate surface finish after honing. With these dimensions to correct tolerances then running in is virtually obsolete.

Last edited by Simon Ratcliff; 11/21/17 7:40 am.

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