Trouble with oil space rings

(Jim XK140 FHC) #1

Having trouble with the oil spacer rings, what is my problem?

(Jim XK140 FHC) #3

With the compressor as tight , as I can get it , it is still standing off the piston. The picture shows 35 tho feeler gauge in the gap

(Roger King) #5

Jim, are you gapping the rings, or are they supposedly correct? I always check ring gaps myself and adjust if necessary with a diamond wheel in a gapping jig.

To check gap, place a ring carefully down into the bore and push it down gently about 1" into the cylinder using the top of an inverted piston. This should get it square in the bore. There should be a fine gap left between the ends of the ring, which you can measure with a feeler gauge. If there isn’t, and the ends overlap (or have a huge gap), you have the wrong rings for your oversize. The paperwork that came with the rings should give gapping dimensions.
The scraper rings that you are looking at in the video often fit a bit differently from the compression rings. What they must not do is hang up on themselves once they have heat-expanded in the bore. You could try installing one scraper ring on a piston and compress it into the bore, then check with a torch that there is still a gap between the ends - but you should be able to tell if things are right by the method I gave at the top of this. Another thought - oil scraper ring inserts sometimes interlock in position. Check you have them assembled exactly as in the instructions, there are various ways of doing it.
Haven’t actually played with Jag rings yet personally but have fitted countless other makes - they can be a bit quirky. And any manufacturer who numbers their cylinders after industrial diesels is definitely on the spectrum.

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(Jim XK140 FHC) #6

Here is a vid of all the checks I can think of.

(Paul Wigton) #7

That gap should be ~0.003"/inch of bore diameter.

(Phil.Dobson) #8

the ring compressor needs to be parallell. i ‘sit the piston’ on the block (rod hanging into the bore, piston offset) then lightly tap the ring compressor down until it touches the block. (not so easy to describe) then final tightening of the ring compressor. then just do as paul w says

(Jim XK140 FHC) #9

Mmm… the ring gap when in the bore is a little tight , I have 12 and it should be 15-20 . That is odd as my bores will be worn a little so should be a generous gap ?
Phil I have tried as you describe , but I still feel it is too big , I have levelled it up and put as much force as I dare to tap it home .

(Robin O'Connor) #10

It sounds to me like you have an interference with the depth of the piston groove? Either that or things are just not quite sitting correctly. Have you tried another piston? I know the definition of insanity is tryin the same thing over and over but you have six of them to do :slight_smile:

(Paul Wigton) #11

Good point. If, when you put the ring into the groove upside down, does if all fit under the skirt of the piston?

(Jim XK140 FHC) #12

Is this what you meant Paul ?
When I fit the oil ring and both spacers it is definitely noticeably proud . Hard to show on a photo.

(Roger Payne) #13


Is that a 3.4 litre 9:1 cr piston?
If so, can you advise part number stamped on the top, and a few more photos.
Trying to identify the differences between the four or five different part number 3.4 litre 9:1 pistons, first fitted to a handful only 1953/1954 XK120SE with -9S engine numbers.


(Mike Eck) #15

Hi Jim,

I once tried to use rings like that in my
3.4 Mk1. The rings consisted of 3 pieces, two thin scrapers and a
spreader (wavy thing) that fit behind them and pushed them outwards. The
scrapers stood proud of the spreader, so when installed the spreader needed to
be smaller than the cylinder. Assembled that way, there was no way I
could get them into the bores using my ring compressor. As a reality
check I tried to simply insert the wavy thing in the bore, without the
scrapers. I put the two ends together with the rest of the loop up at an
angle, and used an inverted piston to push the loop down so the spreader was
level. It took a lot of force, and when I looked at it I discovered that I
had scratched the bore getting it in. There was no way that the spreader
could be compressed any tighter, as it would need to be when it was installed
with the two scrapers. My engine had already been bored .040” over
so it wasn’t a case of incorrect oversized rings. My solution was
to cut the ends off the spreaders, since that was the only way I could get the pistons
into the bores. Bad idea, since that rendered the oil rings totally
ineffective. I was a teenager at the time, with severely limited funds,
so my solution was to buy a set of J. C. Whitney .020” over rings for $10
and use the oil rings from that set. They worked fine for the next
100,000 miles.

To summarize, I still have no idea how to
get those rings into your cylinders. Try putting the spreader in alone
and see what you learn.

Mike Eck

New Jersey, USA

'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2

(Lee140FHC) #16

They sure look like 8:1 pistons to me…also, I had mentioned earlier that I went with Hastings single-piece oil control rings…SO much easier to install.

(Roger King) #17

Jim, if you’re re-using old pistons, is the lateral clearance for the rings still OK with your new rings?

(Jim XK140 FHC) #18

I believe the clearance is 1 to 3 thou. I can’t get a 3 thou feeler in so I am ok .
I think I have got to the bottom of my problem. 5865 was the first set I was supplied which is listed for 120 140 150 and others
5782 is my new kit with the oil ring is much thinner and fits below the surface ok.

(Roger King) #19

Aha. Looks like you ordered a ring set for a 4-groove piston:

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(Jim XK140 FHC) #20

They told me the kit was the same, just dont use the forth ring.
It is a lot easier with the right parts, that is the second time they have done that to me, they supplied OS crank bearings instead of standard.

(Robin O'Connor) #21

Great to hear that you have a resolution on that problem.

(Jim XK140 FHC) #22

Thanks for all your contributions.
To recap
3.4 standard bore 3 ring
Hastings 5782
I think Grant are 1036 prefix C is chrome, not sure want prefix P is.