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Re: Cylinder bores

Hi Hedd,

An entirely different possible use for this 'Timesaver Lapping Compound' - I want to gently remove a thin very old (1950's) top layer of paint to reveal the sign written paint layer below, as on a sign written van door. Any thoughts on whether you think this compound may have that desired effect on old paint ? It's probably going to be a case of me buying a tin and giving it a try. I see Craftmaster Steam Supplies sell it for £14.95 for a 3oz tin.

Jeff.

Location: Almost but not quite, the far North East of England

Re: Cylinder bores

Save yourself grief, do it right, do it once is the best way.

Location: Centre of the Universe

Re: Cylinder bores

Where has all this "impecunious enthusiasm " gone? I thought Austin Seven enthusiasts liked the tinkering aspect of owning one. 💣

Location: Sheffield

Re: Cylinder bores

Dave Wortley
Where has all this "impecunious enthusiasm " gone? I thought Austin Seven enthusiasts liked the tinkering aspect of owning one. 💣



At Last, a man after my own heart! This sort of makeshift, shoestring engineering idiocy was what Austin Seven owning was all about when I started playing with them 45 years ago!

I should have explained that the reason for building this engine on the cheap (my budget is £100)is that the RP's engine now has about 80,000 miles on it since its last major overhaul and is starting to rumble a bit. As this is the original unit that was fitted when the car left Longbridge I want retain it and do a proper job on it. I need a temporary engine to keep the car on the road, but my previous spare suffered a crankshaft failure and was knackered anyway. The cheapo project is a replacement for this.

I have built up a couple of engines this way in the past. My only problem with this one is that the available parts are far less worn than in previous exercises and I'm concerned that the pistons may be a bit tight for the bores. I have a set of +040" pistons, but they're much too loose.

Location: Herefordshire, with an "E" not a "T".

Re: Cylinder bores

What kind of honing tool do you have Martin?

Re: Cylinder bores

Martin , I am with the others as regards to rebore and new piston if you want to be sure your rebuild will be ok first time. However if you are like me and do not take your time and effort into account go ahead the most you can loose is the time of doing it all again together with the cost of rebore and new Pistons together with a few new gaskets.
As to your bore measurements over size normally go +2. +4.+6. Try measuring more than one bore and measure top bottom and centre of the bores. Also measure different diameters as worn bores tend to go oval in shape.
Following that assemble your block and piston ( with rings) together with rods to the crank and crankcase well lubricate bearings,big ends and bores and see how it turns. It should turn very freely as there is no compression.

John Mason

Location: Nottinghamshire

Re: Cylinder bores

Martin

Mr Dunfords question in pointed.

We made the bores on my traction engine which were 80tho barrelled, both round and parallel using a 3 armed lorry honing tool and much time and measiring. Took a set of new stones mind.

3tho should be 10mins work

Re: Cylinder bores

Martin

What we dont know is what size the +60 pistons are in reality

Just been reading an old book here.

It says cast ali pistons need 1.5 to 2 tho clearance per inch diameter. As a general rule.

Lets say 2. This suggests 5 tho clearance needed give or take max.

You can easily measure this with feeler gauge. Measure top. Middle bottom.

5 is a nice easy number.

4 is in the range. 3 is too tight.

Re: Cylinder bores

Courting controversy and with the greatest of respect to the other contributors on this thread I say why not. It appears that Martin is well aware of the limitations when going down this route, and as anyone who has been around Austin sevens for any length of time will know nice loose clearances make for a quick engine. I have on more than one occasion gone down this route on a budget engine rebuild with success. So IF the bores are round and parallel why not, sure the life of the engine will be reduced but as long as you accept this whats the problem. I disagree that it will reduce performance in fact I suggest it may actually improve performance, my quickest race engine ran with quite large clearances, and those who know me will appreciate just how quick that engine was.

Location: NZ

Re: Cylinder bores

Ruairidh - it's a basic, new 3-arm honing tool. I've run it through just enough to clean off some very light surface rusting.

John, as I mentioned above, this is meant to be a cheap stopgap so I can spend some real money on the RP's original engine. I simply can't afford a full job on two engines.

I've measured all four bores top and bottom, side-to-side and fore-and-aft using a vernier caliper. 13 out of 16 measurements were 2.257", the remaining three, all on the rear cylinder, are 2.260" to 2.261". I've checked for lips and barelling with a back-illuminated steel rule and the bores appear to be straight.

I have standard, +020", +040" and +060" pistons to hand. The +060" are a good fit and slide comfortably with light resistance when fitted with rings.

Given that the valves and seats are clean and in perfect condition, I'm pretty confident that I have a reconditioned nominally +060" block with close to zero miles on it.

I'm not worried about potential lack of compression; it's whether the apparently slightly undersize bores will cause trouble, but Hedd's response probably addresses that.

Location: Herefordshire, with an "E" not a "T".

Re: Cylinder bores

I would hone it a little more and suggest it will be fine for your stated purpose.

Re: Cylinder bores

Ruairidh Dunford
I would hone it a little more and suggest it will be fine for your stated purpose.






Like Mr Trump, Ruairidh, I'll hire and fire experts until they give me the answer I wanted in the first place!

Location: Herefordshire, with an "E" not a "T".

Re: Cylinder bores

Like Mr Trump, Martin, you missed out loads of facts when you asked the opening question!

Re: Cylinder bores

Since I'm not an expert I'm in no danger of being hired or fired. The Austin 7 engine is a simple robust device which is why so many have survived despite being worked on by people like me. I learned everything from the Austin Seven Companion book which is full of advice for the impecunious or mean. Have a go, it's all good fun, and it will probably work.

Location: Isle of Wight

Re: Cylinder bores

Martin Prior
Ruairidh - it's a basic, new 3-arm honing tool. I've run it through just enough to clean off some very light surface rusting.
.


Hi Martin,

Have you bought a honing tool, or a deglaze bar.

A £30 deglaze bar from machine mart. Will not be man enough to hone.

It would probably brake the three grinding stones of there glued basses before you can take 3 thou out. And would probably take six weeks to do it.

A deglaze will help the rings bed in. But if you have 3 thou variation I doubt the bores were done with an experienced hand. So would expect there to be plenty of gaps for the rings to run over.

Although for what you need this won't really matter.

Location: Huncote on the pig

Re: Cylinder bores

Tony,

It didnt take 6 weeks to take 80 tho out of the bore of my traction engine. That is 8 inches diameter.

I should know, I was paying by the hour.

Re: Cylinder bores

A vernier is not accurate enough of checking bore diameters and I expect the sizes you have taken may be misleading, you would be safer checking clearances as Hedd suggested

Location: NZ

Re: Cylinder bores

Hi hedd,

Thought you sed you used a honing tool.

A 3 finger deglaze bar from machine mart is not a honing tool.

It would take weeks to take out 3 thou,

Tony.

Location: Huncote on the pig

Re: Cylinder bores

So the standard size for a Cylinder bore is 2.2" not 56mm, if its the latter they are probably .050 oversize. I'm sure this is common knowledge in these parts, but just checking...

Location: Fremantle Australia

Re: Cylinder bores

While it might not stand accounting scrutiny of the time spent, cobbling up an engine from discarded bits can be very satisfying when successful and is in the Seven spirit of old. If things rust through or go bang from other causes the loss is less. And if your own labour not a big deal to repeat.

Vernier callipers tricky; the slightest pressure leads to errors. Difficult to assess cyl state without mikes, and then using separate internal and external mikes can accumulate errors. Bore size and wear can be established with lengths of nail, wire etc fitted to length or some simple telescoping gadget and measured with the same external device as used for pistons. The exact point of maximum wear can take some searching. Measuring change of ring gap gives an indication, although taper will be more than 1/3 the change. If an engine has genuinely parallel bores, seems a pity not to utilise. Mikes now very cheap, esp 2nd hand inch.

There are various reasons bore may not be a standard oversize. Split skirt pistons typically need and have at least .003 clearance across gudgeon and .0015 across faces. The skirt needs only collapse .0015 as prone to do and may enter .003 under bore. The diameter at gudgeon may be greater than skirts. Must not operate with small clearance across and near gudgeon axis. I don’t think Austin ever fitted split pistons and do not know what typical life of split pistons is; solid ones are everlasting. Inspect closely for worn grooves and cracks at the ends of the split. Significant collapse suggests high mileage.

Bores can be accurately expanded with a rigid hone but few have these. It is not good practice but if already parallel with care could expand bores .003 with a ring resurfacer hone, which you apparently have.(Not a ball hone!) These are used after rebores to finish and remove nearly this. A range of stones are available. An elaborate cleaning with soap and water after any honing is recommended.

My limited experience has been that with the original Austin wide rings satisfactory operation and oil consumption is obtainable with considerable wear, but I found low oil consumption elusive with modern narrow ring split pistons even after rebore. Using one piece oil rings.

I don’t know what piston clearance and bore taper is considered the tolerable max for ordinary Sevens. For cars in general .007 taper was often quoted as rebore limit, but now much less. I had an engine with bores .003 barrel shape, pistons generous clearance, and consumption was notably high.

Clearance across gudgeon diameter can be increased by hand. (Some aftermarket solid pistons were round and needed this treatment to match the original Austin ones)

The one oversize cyl is a puzzle. Reminds of a mechanic we knew who used to do rebores on owners premises using a coarse rigid hone. Said he went for afternoon tea, came out, and did a cylinder a second time! Perhaps that is why the block has been set aside.

Location: Auckland, NZ

Re: Cylinder bores

If you must do it with the 3 stone springy job then do it lightly, fit the pistons and rings and push each piston 1" down the bore. Fill each bore to the brim with paraffin and see how quickly it leaks down.

Re: Cylinder bores

Tony betts
Hi hedd,

Thought you sed you used a honing tool.

A 3 finger deglaze bar from machine mart is not a honing tool.

It would take weeks to take out 3 thou,

Tony.


Call it what you like. It was a 3 finger tool. But a commercial vehicle one, not a car one.

It took a bit of time. But nothing like the time you suggest. Done in situ with a large electric drill drive, but operated by a man.

Re: Cylinder bores


Thanks Hedd. I've only had the chance to check one bore so far, but on that I can get a 0.0015" feeler in on both sides of the piston all the way down. 0.002" won't fit at any point, so that appears to confirm my suspicion that the bores are a little tight.

I'll have a gentle go at it with the three-armed thing (hone or not?) and will see what happens.

Location: Herefordshire, with an "E" not a "T".

Re: Cylinder bores

Mark Dymond
So the standard size for a Cylinder bore is 2.2" not 56mm, if its the latter they are probably .050 oversize. I'm sure this is common knowledge in these parts, but just checking...



Now there's an interesting bit of confusion to add!

I work in Imperial, so I'd cheerfully assumed that the original bore was 2.2" - it had never occurred to me that usually-quoted 56mm isn't an exact conversion.

So, can anyone confirm with absolute authority that a +060" rebore should finish at 2.260"?

Location: Herefordshire, with an "E" not a "T".

Re: Cylinder bores

2.200" converts to 55.88mm

56mm converts to 2.2045" only 0.0045" ( 41/2 thou.) oversize from standard.

Ian Mc.

Location: Shropshire

Re: Cylinder bores

I had always understood it to be 2.2 bore. 3 inch stroke.

This works out to be 747.48CC assuming pie to be 3.1415.

If you do it with 56mm and 76mm you get 748.73CC

That seems to confirm the imperial dimensions.

Re: Cylinder bores

Martin,It seems a lot of interest in your project and although I agree with some of the opinions as to "doing it correctly" I understand your initial request for an economic rebuild option. There is obviously some confusion as to the measurements of both bore and piston diameters and their compatibility,there is really only one definitive answer and that is to get both measures professionally. I just googled Precision engineers in your locality and there would seem to be quite a selection. I'm sure one or two would measure the dimensions for you at a reasonable cost. Camcraft in Bishops Frome may be a good start. Once you have good compression, do you have a crank and rods good enough to take the load? Trouble is when the ball starts rolling nobody can say where it will stop. Best of luck.

Location: Piddle Valley

Re: Cylinder bores


Thanks Peter.

I think that the excitement caused by bores and pistons is enough for one decade!

The full horror of what I'm doing with crank and conrods will remain a secret between me and my engineer's blue!

Location: Herefordshire, with an "E" not a "T".

Re: Cylinder bores

Hi Bob

Thanks for the tip. However my Phoenix crank and matching Austin conrods were supplied by a very well known Austin 7 engine builder and I know that they are OK. Like Martin, I cannot get more than a 2 thou feeler between the piston and the bore. I intend opening this out to 5 thou and see how the pistons slide in the bore.Also, due to inexperience I did not gap the rings. All these good things will be done when I re-build the engine for the second time.

Hedd, thanks for the tip about the Timesaver compound. Appears to be a great product. If my big ends are still a little tight, I will invest in some, probably the fine grade.

Location: About 40 km SW of Limoges

Re: Cylinder bores

TIMESAVER LAPPING COMPOUNDS

order on line
add to cart
yellow can

PRECISION FINISH ON BEARING SURFACES
GUARANTEED NOT TO IMBED - WILL NOT CONTINUE TO CUT!

Please see Precision Finish Booklet (PDF)

Timesaver Lapping Compound does not contain emery, aluminum oxide, silicon-carbide or similar charging abrasives.
They are unconditionally guaranteed not to imbed into any metal surface.
Prepared in powder form, to be mixed with oil as used.
Timesaver first acts as an abrasive, then the particles diminish to a polish, and finally to inert material.
Directions for use in each can.

.........So hopefully does exactly what it says on the tin.....?

Location: Herefordshire, with an "E" not a "T".

Re: Cylinder bores

Mine is not in a tin. Its in a plastic box

Location: not north wales any more

Re: Cylinder bores

Location: Herefordshire, with an "E" not a "T".

Re: Cylinder bores

hedd jones
Bob and Dave. Please research the 'Timesaver' it does not embed or continue to lap.


Hi Hedd,
Which grade of Timesaver would you suggest for Martin's job - there are 4 listed.

Regards,
Steve V.

Location: Polegate, East Sussex, United Kingdom

Re: Cylinder bores

More info on the incredibly useful product.

 photo 113CBEE0-3F38-473D-9FA4-AB0B173043EF_zpsgr5vp2ml.jpg

 photo 816EB107-9978-41B2-B890-D92F053B3FDB_zpsxdtnugsd.jpg

Re: Cylinder bores

Stephen Voller
hedd jones
Bob and Dave. Please research the 'Timesaver' it does not embed or continue to lap.


Hi Hedd,
Which grade of Timesaver would you suggest for Martin's job - there are 4 listed.

Regards,
Steve V.


I use the medium on bronze and it works out well. But I would be tempted to use the fine on white metal. But its all about how much material you need to remove. If Martins conrod is hellish tight starting with the medium may be an idea.

In anycase the paste gets finer as it is used, to a point where it is almost doing nothing.

Location: not north wales any more

Re: Cylinder bores

Thanks Ruairidh and Hedd.

Steve V.

Location: Polegate, East Sussex

Re: Cylinder bores

For info. Adam Brown who runs Craftmaster has a ruck of vintage tack. Including a 1930 AE Chummy just like mine.

Location: not north wales any more

Re: Cylinder bores

Strayed somewhat from bores!

The 1920s idea of fitting b.es. so rods just drop was based on scraped bearings with high spots. If the crankpin unworn all around, it would now be considered too close for precision mated surfaces, given todays trend to hard use.

Applied to cars driven reasonably, belling must greatly reduce life. Close fitted parallel bearings looked fine on my RP held often at 50 mph and 30 mph in 3rd, 35 on occasions. I guess adequate piston side clearance is a factor.

Years ago significant filing of b.e.s and rescraping was regarded as a ritual part of any overhaul. The idea seems to have been to remove the hard abrasive layer which forms without a filter and thus extend crank life. (But in any case, with reasonable oil changes, the wear life of Seven cranks will likely extend beyond their fatigue life!)

I don’t know what standard practice of machinists is, but it would seem prudent to provide slight relief at the parting line, as built into shells.

Location: Auckland, NZ

Re: Cylinder bores

At the risk of becoming a "cylinder bore" I thought I would share a recent experience.
I am in the process of rebuilding my RP engine. The engine was as it had finished our trip from BA to NYC in 2013. Although it produced a miasma of oil haze in the cabin, it went like stink, but the lubricant inhalation was probably not conducive to good health, so in anticipation of a trip beginning with the 750 Euro Tour to Salzburg and then down the Adriatic coast to Albania, by ferry to Italy and then Spain and home from Santander, it was time to rebuild.
I obtained another block and had it bored to +40, pistons and rings supplied by Jamie at the Seven Workshop. The actual bore size being as required on the ring packet. The advice from Jamie was to gap the rings 3 to 4 thou, however once bored and the rings inserted, the gaps were already 8 to 9 thou. I spoke to Jamie then went back to the machine shop, Guardias engine Services, where the bores were checked for finished size as well as the pistons and rings. The bores were actually a fraction undersize, the pistons exact, it turned out to be the rings that were too small/short.
Having discovered the source of the error I asked both for advice on what to do. Guardias are of the opinion that 9 thou is fine, he suggests 12 on a normal road engine. He has machined Austin 7 race engines with less clearance, but his experience is that it promotes bore and ring wear. Jamie would have replaced the rings if I wanted to try others, however I have settled for the existing items. There are two compression and two oil control rings per bore in split skirt pistons.
I want to emphasize that I have spoken to the supplier and engineer, both of whom were patient and thoughtful in giving their opinion and advice, I have no issue with either. Guardias say that in his experience of dozens of rebored engines each year, the rings are often supplied shorter than required to allow small gaps. Jamie reports that he is supplied by two different manufacturers and passes on their recommendations as to bore size and ring gaps.
I suppose you pays your money and takes your choice! Watch this space,in this instance 0.009".
(Answers on a postcard please to MR R.Dunford, Up North, Beyond the Artic Circle, Kiltshire)

Location: Foggy Cotswolds

Re: Cylinder bores

There are many ways to skin a cat, my preference is to measure each piston individually and then bore to suit. The rings can then be adjusted, if required, to suit the bore.

The gap you have is not extreme by any means and will most likely serve you well.



p.s. I used to send my Grandmother a postcard from every holiday - another tradition bites the dust!

Re: Cylinder bores

The ring gaps in my current Chummy engine are 0.010" - 0.012". I didn't build this engine, but a well respected Austin 7 man did. Runs well, with no problems.

Location: Wales

Re: Cylinder bores

Ruairidh
Where did you find the 2 pages of info on that Timesaver compound.......I would like to do a printout but cant find that info on the company webpage.....also just trying a print of the forum page just wants to print the entire forum subject.

Dennis

Re: Cylinder bores

It came with the powder when I bought it Dennis.

I will email you a copy of the photos to print out.

Re: Cylinder bores

At one point it was very difficult to get. Newman tools in the states have all the guff on their website.

Re: Cylinder bores

I have often been annoyed with replacement rings for other makes. To simplify work for mechanics and avoid comebacks rings were supplied gapped for smallest tolerance bore and gaps are generous on others, esp any honed. For worn engines many ordered rings .010 oversize.
Most textbooks and ring manufacturers recommend at least .003 per inch dia, altho the Seven and other oldies originally much less. Quite large gaps make surprising little difference to performance. The used refit limit for many cars was given as about .030. ACL ,major manufacturers in Oz, quote .005” per inch plus .001 as max for new rings pus another .010 for rehoning and wear. I supect large intial gaps are favoured for modern very slow wearing rings whereas most c.i.rings develop extra gap in first 10 minutes.

Location: Auckland, NZ

Re: Cylinder bores

Hi Martin and others

My new Moore & Wright digital calipers and my new 3 prong glaze buster/hone have just arrived via Amazon, so have been doing a quick check. Initial results are cylinder bore in block 2.2285" and piston dia below rings at 90 deg to gudgeon pin 2.2285". No wonder my engine was tight. I hasten to add that the block is one that I obtained with the rest of the heap of spares and had already been bored. Not being used to A7 engines, I didn't think to check the bore size, but as it came with a new set of +30 thou pistons, I assumed that it would be OK. Anyway, now have to hone the bores to give the correct clearances.

When searching the internet for a 3 prong hone, I noticed that a couple of suppliers recommended using brake fluid as a lubricant whilst honing. Did you use anything as a lubricant when honing out your block?

Location: About 40 km SW of Limoges

Re: Cylinder bores


From the sound of it, Tony, you did well to get the pistons in at all!

I used a few drops of light machine oil while honing, but I imagine that brake fluid would be just as good.

Location: Herefordshire, with an "E" not a "T".

Re: Cylinder bores

I am very surprised, Tony, that you are able to obtain an accurate reading with a digital caliper.
I recently purchase a brand new bore gauge / comparator from Machine-dro.co.uk for around £40. Superb quality for the price, with a range from 2.0" upward.
The obvious usefulness is that it will accurately measure the whole length of a bore, ovality etc.
Chris

Location: Melton Mowbray

Re: Cylinder bores

Hi Chris

I have a set of locking telescopic spring loaded bore measuring gauges. Basically a T shaped thing, the top of the tee being the spring loaded bit that fits inside the bore and the vertical of the tee being the handle containing a threaded rod that locks the bit that fits in the bore in position. Using this combined with the digital caliper allows the measurement of the bore at various points over the full length. I am sure that your bore gauge will be a bit more accurate but I think that what I have will suffice for now. I will insert a piston without rings in the bore tomorrow and see of I can get a feeler gauge between the piston and the bore and also carry out a more comprehensive survey of the diameter of the bores. Hope this makes sense!!!!!

Location: About 40 km SW of Limoges

Re: Cylinder bores

I have the same gauge as you Tony. It's tricky to use but with care it gives good results indeed.

Location: Unsunny Brittany

Re: Cylinder bores


This discussion seems to have gone full circle!

I'm with Tony and Renaud.

We've already established that with care, calipers can give an accurate result - mine isn't even digital!

Location: Herefordshire, with an "E" not a "T".

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