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molemot

Cylinder liners and piston clearances

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Hi

Today I measured my old Lotus liners and all 4 measure 3.7525


 

"Belief is the enemy of knowing" - Crrow777

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Upgrade today to remove Google ads and support TLF.

Had a chat with Steve at S&J this morning. He tells me that all the Esprit specialists source their liners from the same place, and said he'd used over 50 of them himself and sold lots more, with no previous complaints. He said he would check all his stock...especially the 4 he was about to install! At least a genuine reason for my 3&4 seizure has been found. I think that without the heat and stress generated by a lengthy period at 200+ horsepower, no problems would have arisen.And how many people go that fast for that long? Normally it's a quick burst followed by braking, so the engine doesn't get the same degree of sustained high power as I gave it.

Anyway, I've got all the liners out and the old sealant cleaned off now; that Loctite 572 really holds them in...not much chance of the liners shifting if you turn the engine with the head off with THAT stuff! Now have 12 liners in review order, but since they are all the same height I can't say "Tallest on the right, shortest on the left, in single rank, SIZE!" Before I get to the ones I'm intending to install, I will be able to get a good feel for what's needed in the honing process. Another new skill!!


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Steve,

Did you obtain both the bigger pistons and liners from the states? And was the supplier JAE?

It seems you have a reliable tested setup and I'd rather follow that path than shell out for dodgy UK liners and then have to pay someone to machine them. I accept that some honing will be required to achieve a particular clearance though. In the long run it is probably a cheaper option.

Thanks

Ambrose

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Typical finish honing after rough boring and honing will increase the bore by around 3 to 4 thou inch / .075 to 0.1 mm. This would move the rough finished sleeves you have been supplied with to the correct bore dimension.

The fact that the supplier has provided a set of sleeves and pistons without clarifying or appearing to even understand they are not a finished match set is the concern. But then precision machining and matching of components and why you do it and how you specify it is not understood by many even those in the business who should know.

cheers

Rohan

forgot to mention

Typical professional honing equipment will remove around .010 inch of material a minute so it is not a long process.

Home hand held drill driven honing tools are really just toys and glaze breakers at best. Take your sleeves to a professional engine machining shop with the right equipment to produce a straight and circular bore with the correct diameter and surface finsh

Find a race engine machining shop that is interested in doing historic racing engines - these are the places that care and do the best work ( if not the cheapest cost)

cheers

Rohan

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Hi Ambrose

Pistons & (rebored) Liners were supplied, ready to fit, by 'Claudius'. (I think a well known Californian dealer) Pistons are forged and manufactured by Venolia (seem to be well respected in the performance community if you look at their website - They also list 'Lotus' fitment in their catalogue).

Although its a few years ago, I paid around

Edited by 910Esprit

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Thanks for the information Steve, I'll see what the current price is for matched ready-to-fit set of pistons and liners. Given that the liners from UK suppliers will likely be 250 and that a set of UK forged pistons upwards of 450 the potential extra expense of shipping a known good solution from the states is likely to be a small percentage of the total cost... and worth paying.

Regarding the honing of freshly acquired non-matched liners, these UK liners are deliberately too small since it is expected that you hone down to achieve a particular clearance with your chosen piston - this and the amount now confirmed by Rohan's post. I have also looked up honing in my "Four Stroke Performance Tuning" book and I'll quote since it may help John

"The actual honing process varies a little from engine to engine but a fairly standard method using the Sunnen CK-10 automatic hone is as follows. First using 220 grit stones, about 0.003 in of material is removed to bring the bore to 0.001 in from its final size. Then another 0.0005 in is taken out with 280 grit stones and finally 400 grit stones are used to bring the bore to its final diameter. This results in a very accurate bore with a fine finish that requires very little break in"

So the options appear to be either buy the UK liners and hone them to suit or buy a matched piston liner set from a knowledgeable supplier. I am surprised that some UK suppliers are not stating that the liners they sell are only rough honed given that a lot of their customers are non-expert enthusiasts (like me).

Ambrose

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Ambrose may what you are saying maybe was right about 20 years ago but liners should be supplied correct to use. The suface rougness is something else that should be correct too. Should be rough enough with the correct cross hatch pattern to retain an amount of oil.

Buddsy


 

"Belief is the enemy of knowing" - Crrow777

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Buddsy,

The problem is that the suppliers do not give enough information about the liner. ideally they would either state that the liner is supplied rough honed to a particular diameter and tolerance, or that the liner was ready to fit of a particular diameter and surface finish(10-12 micro-inches a good compromise according to my book). The problem it seems to me with ready-to-fit is that it may narrow your choice of pistons, a JE piston will most likely require a different clearance to the original cast or a forged Mahle. The supplier would then need to stock different sizes depending on the piston being used. It seems quite reasonable/sensible for the supplier to either offer the rough honed undersize liner or ready-to-fit matched piston liner assemblies.

I suppose you could argue that the liner should be a ready-to-fit straight replacement of the lotus part which is reasonable though the lack of availability of A or B grades communicates to me that either a 'one size fit all' approach has been taken - which strikes me as being a little risky and not exactly exacting or the liner needs honing.

Still, Im much clearer about the way forward now and even if I go for the matched piston-liner assemblies I'll be sure to measure everything at least twice!

Ambrose

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When I had a chat with Steve at S&J, he seemed to think that the liners and pistons he was selling were matched, in the sense of the piston/cylinder clearances should have been correct. He certainly didn't think he was selling parts that were "rough honed " and had to be honed to size by the purchaser. Thanks for the reference on honing...as you might have thought, I've been devouring everything Google can find me on the subject!!


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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As Molemot says the SJ liners we are discussing are for the standard cast pistons not the HC ones or anything else. Other pistons will require a liner to suit that.

Buddsy :)


 

"Belief is the enemy of knowing" - Crrow777

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John,

I assume that you are referring to the Omega forged pistons you obtained from SJ being matched to the liners rather than your original cast pistons. Anyway it sounds to me like you have a path to follow with your honing experiments and a method to measure the results so it should all fine in the end...

Incidentally you may find this interesting,

http://www.guy-croft.com/viewtopic.php?f=1...it=honing#p5899

and more of the same

http://www.guy-croft.com/viewtopic.php?f=1...it=honing#p5318

In fact the whole site is very informative and the chap certainly seems credible.

Ambrose

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Thanks for that, Ambrose...just love the toilet brush for bore cleaning, brilliant idea!! Much better than the old nail brush I've been scrubbing away with..and you're right about the liners supposedly being matched to the Omega forged pistons, not the original cast Lotus items. My measurements show they aren't matched to ANY specification, be it Lotus or Omega...hence my problems. I'm intending to start off honing one of the old, original liners to get some idea of speed, stroke and rate of cut..then have a bash at one of the new liners from the first iteration which seized..finally, when I'm up to speed on the technique, I'll start in on the ones I'm going to use. Got a nice fixture all made up to hold the liners, with built in lube feed, and all I'm waiting for now is for la Poste to deliver the hone...!! Got bags of snow here at the moment, so it might take some time!!


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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IF the SJ liners are supposed to be finish honed for the standard cast pistons then SJ should be able to tell you the bore size and torelance and surface finish of the sleeves and the diameter and tolerances of the standard cast piston that matches the sleeve and the resultant tolerances on the bore clearance and how that is within the required specification. If SJ cant tell you this data then they are not finished sleeves as SJ believed.

From the bore measurements and tolerances data supplied for the measured sleeves they would not fit any piston specification I am aware of. The only pistons that would fit these sleeves would be fractionally undersize and no one makes undersize pistons that I am aware of. The tolerances on the bore between the sleeves would also require individual sizing of pistons to match the wide variation in the sleeves bore to get acceptable piston to bore clearances. That is why I have said they are not finish honed or matched to any set ot type of piston.

I suspect a proper measurement of surface finish would also demonstrate they are not finish honed. i.e.The surface is both too rough as only coarse stones for an initial rough hone have been used and the bore has not been finish honed with fine stones and also not plateau honed and brushed to remove the sharp peaks.

Very difficult to achieve the correct tolerance and surface finish with home honing tools but if you have got the time and skill and measuring equipment worth a try I guess

cheers

Rohan

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Rohan...dead accurate summation, although I would say that they have been finish honed, but not plateau honed. The liners I have are not the correct size to fit ANY piston intended for the Esprit. Cockup, methinks. As for honing them myself, well I'm a pigheaded sort of bloke and like to do EVERYTHING myself..so I'll give it a go. If it becomes obvious, after attacking the scrap sleeves, that I'm not going to be able to do it, I'll hie mesel tae a machine shop with explicit instructions!!


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Time for a bit of an update..!! The idea of using my pillar drill to drive a hone failed miserably, as in the event I couldn't get a long enough stroke; maximum I could get was 2" and it needed at least 3". Anyway, nothing ventured, so I tried freehand, with the liner holding jig at about 45 deg held on a Workmate. A mixture of 30w oil and kero to lubricate, in went the hone and away we went .. round and round and up and down... all going nicely! Now, I had read in my researches that one should never stop the hone rotating before withdrawing it, as that way one left scratches up the cylinder walls..which is exactly what one was trying to avoid. So, in a fit of geriatric lunacy, I withdrew the hone whilst it was still going round..and the world went mad!! Of course, this being one of the tripod, spring loaded type hones...as soon as the pivot point of the stones came out of the top of the cylinder....!!!

It sprang apart, my nice perspex jig front cover flew in splinters across the workshop, followed by bits of shattered honing stone and the odd piece of mangled plywood. No damage to self, fortunately. Older and wiser by now, I changed the stones and carried on, checking the measurement with my bore gauge as I went.

In the end, I had managed to hone one of the set of cylinders that seized out to the correct size. Sadly, I found it impossible to get a decent surface finish, and it became apparent that this was not going to be possible with the equipment to hand. I was now faced with finding some machine shop who could do the job...remember, my workshop is in France and I didn't even know the French word for "hone"..and it doesn't feature in normal English-French dictionaries! (For anyone interested, the word for "honing" is "alesage" with an acute accent over the "e"!)

After much searching, I found a precision engineering outfit at the other end of my village, and went down there for a chat. Spoke to the "Man in the Office" and explained what was necessary..he thought it shouldn't be a problem, and they would be done by the end of the next week. O Joy!! Success....or so I thought. 0830 the following morning, the phone rang..it was the "Man in the Office" on the phone; some problem had arisen...so I dragged myself out of the pit , dressed and drove to the Works. Met the "Man in the Workshop"...found that the French can do the tooth-sucking bit with just as much emphasis as the Anglo-Saxons!! After some more chat, it appeared that they couldn't do the job, as they couldn't mount the liners on to their CNC machine. But..they did suggest somewhere else that might be able to do it...

So off I trogged to this other place, a 35 mile drive....they were very helpful and agreed they could do the task...but wanted 170 euros for the job!! At this, my Caledonian blood rebelled, so - in the famous words of the "News of the World"...I made my excuses and left. After some phone calls, I have shipped the 4 new-but-defective liners back to Steve at S&J (which I should have done at the outset, except I wanted to get the engine BUILT). He tells me he has inspected his liner stock and, as a consequence of that inspection, rejected all of them..so he doesn't have any at the moment! He has promised that as soon as he has new liners of the correct dimensions he will ship the first 4 to me. So all I can do is wait.....

Edited by molemot

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Hi John,

Sorry to hear the trouble you are having with your honing efforts. It appears to be a tricky thing to do yourself, although I do wonder whether you may have had better luck with the flexihone thing. Anyway I suspect your supplier will make some effort to check the parts they send now...

It may interest you to know that there are MATCHED HC piston liner assemblies (liner,piston,rings,pin) on Ebay direct from Lotus for

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Thanks Ambrose...the new liners from S&J will be finish honed and matched to the Omega forged pistons. The piston box actually states "Bore 95.30" so that's a bit of a clue! The last lot were supposed to be too...but the sizes were wrong. The honing finish was fine as supplied but they'd got the diameters too small...how, I don't know!! I agree about your suggested clearance, 5 to 6 thou is the figure I've seen quoted.


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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A brief update...the new liners from S&J have got as far as TNT at Orleans; they tried to deliver them yesterday but I was out buying stuff for the Edge Devil kit car. They are delivering them tomorrow morning, so I'll have the dial bore gauge in operation in my Goods Inwards Inspection facility..hopefully the sizes will check out and I can have an engine assembly blitz.


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Hi all,

just to put forward another experience for future reference: Im just finishing a rebuild of my 1981 S2.2 after deciding it was a little to tired to go on as it was. I decided to go for the .030" oversize forged piston route ( from the Jensen Healey Preservation Society Shop) I set up the CNC mill at work with a jig and torque plate and bored the old liners within .003" of size, Then using a micrometer adjusting hone ( not the spring loaded type)honed to finshed size, then ran the 400 grit ball hone through to plateau the bore finish. This all went well and the interesting thing is that the recommended piston/bore clearance for the CP Pistons was 0.0025" ( I called and confirmed this) all to do with the new alloys and cam machining of the pistons apparently. Any way Ill be in a better position to give feed back soon since its almost ready to go. The honing process isnt to bad if research is carried out and measurements are taken at regular intervals.

Phil

1981 Esprit 2.2

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What material are your forged piston? If they are ally and your liners are steel I would say your 2.5 thou would be a bit on the tight side. Just my gut feeling!

Buddsy


 

"Belief is the enemy of knowing" - Crrow777

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Hi Buddsy,

While the clearances are tighter than normal lotus recomend, I did check with the manufacturer instructions and they stated 0.0025" . An interesting aside, each piston weighed 94grams less than the original cast type and was a fantastic piece of kit. when placed in the bore after honing without rings, while the skirts had the stated clearance at the tightest point the ovality and taper of the piston was quite a bit more obvious than the standard type. Some thing was also mentioned about Hypereutectic alloy and silicon content.

Phil.

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G'day Guys,

just a quick update on the engine rebuild, The engine runs exceptionally well with lots of torque, at first the accelerator pumps were set way to rich and I ended up winding the nuts almost to the end of the thread (5mm) which improved things lots. The cars covered about 1800km since the rebuild and puts out lots of power,( even with the slightly restricted rev limits) regarding the piston clearances, the forged CP pistons exhibit no slap even when the car is started from cold and rev freely with no sign of raised temperature at all. The SJ tubular manifold seems to work well allbeit a bit loud with the new muffler. I have revved the engine under acceleration up to 6000 rpm a few times (its hard not to get to carried away) and as I said the power is impressive it was worth fitting the oversize stainless valves. It may be my imagination but balancing of the pistons and rods seems to have payed off too, the car is very smooth even at at idle when you can hardly feel it running at traffic lights.

Altogether Im really happy with the result and wouldnt hesitate to reccomend the components used in the rebuild.

Edited by tarnish1

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Mine has 870 miles on it at present, rev limiter is set to 3600, pulls like a train. Will do a compression check at 1000 miles, to see how things are going, but no rattles and all the needles poin to the right places; 60 psi at 3500 rpm and temperature steady at just below 90 deg indicated, even on a nice hot day like today. I'm really enjoying getting the miles on it!! Hopefully, she'll do for a bit...I've just started fitting the 6 speed box to the Audi V8 for the kitcar....


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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