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Re: Rebuilt engine seized

Hi Adrian,
That measurement Should have been point one of a mm 3 to 4 Th.

getting past my use by date.
Cheers Colin

Re: Rebuilt engine seized

This may be a silly question for you.are the pistons split skirt and are they the right way round?
can we see a photo from the valve side ?

Location: Centre of the Universe

Re: Rebuilt engine seized

Good morning Adrian,
"Removed the block to find one of the little ends solid,has anyone heard of this before?"
Well yes! the last two engines I rebuilt I found the gudgeon pins to be unacceptably tight, which is why some time ago I advocated the practise of reaming them to fit.
However my suggestion was met with howls of derision!
"I rest my case M'laud"
J

Location: As far east in Kent as you can get

Re: Rebuilt engine seized

Howl of derision

Re: Rebuilt engine seized

Good morning all
Many thanks for all your replies. These replacement pistons appear to be universal ones as they come with circlips for use with floating gudgeon pins. I wonder if the tolerances are a little tight for our flexible 2 bearing engines. I have found another thread by John Mason with the same issue so it doesn't appear to be a one off. As far as I can remember (you start to doubt yourself after a while) the pins were all well lubricated but were not easy to slide the piston from side to side so tightness could be the cause. Picture below hopefully shows the pistons the right way round or could start another argument!
The pin is seized solid co I cant even get to the pinch bolt to undo it so will have to cut the skirt off.
I will let you know the outcome but will certainly check the fit on the replacement piston.
Many thanks again for all your input.
Adrian.

Location: The New Forest

Re: Rebuilt engine seized

Sorry Alan,
Didn't quite hear that!!!
J

Location: As far east in Kent as you can get

Re: Rebuilt engine seized

Surely worth soaking in diesel, baking in the oven, etc before scrapping the piston? Of am I just a cheapskate?

Re: Rebuilt engine seized

What make of piston are they ? JP pistons used to need a large bore/piston clearance.Looking at them would suggest a low silicon high expansion piston (Dull finish)

Location: Channel Islands

Re: Rebuilt engine seized

Adrian,
A re-metalled rod on a re-ground crank shaft must be able to fall under its own weight,
and the same applies to the pistons they must be able to rock to and fro without
any interference, otherwise they have the nasty habit of seizing solid!
J

Location: As far east in Kent as you can get

Re: Rebuilt engine seized

they look like seven workshop.

but put me right if they are not.

seven workshop pistons were always good quality for the austin 7. although the rings were suspect on there early supply. so be cearful when buying old stock on ebay.

as far as i remember they were always high expansion. so as austin suggests larger sizes should be given a bit more in the bore.

jamie may be able to give you more info on this if they are his pistons.

i did read austins suggestions many years ago. and have in my head something about 2 thou in the bore to every 20thou oversize. although that sounds alot.

so please someone put me right if im wrong.

i think like others im getting past my sell by date.

also only my choice. but i would have aimed at 8 to 10 thou on this type of ring. and ideally closer to the 10 thou.

Location: huncote on the pig

Re: Rebuilt engine seized

Agree with Tony. I've used seven workshop Pistons many times over the years with no problems. I'd use 2 to 3 thou bore clearance and 10 thou ring gap. The gudgeon pins should push in easily, and should rotate with no discernible tight spots. If the aren't like that, don't use a reamer, lap them gently with brasso and an old pin. Don't use grinding paste. If that doesn't fix it, get new pistons.
And, I wouldn't be too bothered about saving the seized piston. I don't think I'd want to use it again.

Re: Rebuilt engine seized

Once again, many thanks for your input.
Tony,you are quite correct the pistons were from The Seven Workshop. The seized one was not salvageable and had to be cut off. The pin seized in the piston and then caused some rotation of the pin in the little end but is ok. The pistons did have a little rock in the bores so I think the machining was done correctly. I will certainly check the fit of the pin in future.
Adrian.

Location: The New Forest

Re: Rebuilt engine seized

Hi All,
there has been a lot talk about Tight pins in pistons and how to remedy this.
the one obvious and not mentioned one is the manufacturer and Quality control,
And this needs to be addressed buy the retailer but they will only know if you take the piston back and not do a quick fix which lets the manufacturer of the Hook

Just my Rant for the Day
Cheers all Colin

Re: Rebuilt engine seized

That is a valid point , Colin .

If no one complains then nothing will improve . Any supplier worth their salt will listen to your legitimate concerns , because their livelihood depends on satisfied customers .

Merv

Location: New Forest

Re: Rebuilt engine seized

Rather than use a reamer on slightly tight piston small ends where there's a risk of the reamer chattering in the softish alloy, I've found that using Flex Hone with a pistol grip drill does the job with a good finish. Flex-Hones are hugely cheaper bought from the USA (even once the international shipping is paid) than buying them here. http://www.ebay.com/itm/1-2-13mm-Flexhone-flex-hone-lifter-bore-240-grit-/351954884089?hash=item51f22555f9:g:SuQAAOSwZ8ZW6bq1&item=351954884089&vxp=mtr

BTW, as the Seven Workshop pistons seem to be a copy/replica of the Hepolite pistons that used to be available, I've always used a scan of the data sheet that used to come in the Hepolite box to gap these pistons and rings in the bores on A7 engines. Here's that scan

Location: N W Kent

Re: Rebuilt engine seized

All parts now on order so with a fair wind should have it back together by the weekend.
I must say, in all my dealings with our cherished suppliers including this case, I have always received first class service and excellent backup when things have not gone according to plan, usually above and beyond what is expected. Long way they continue for all our benefits.
Adrian.

Location: New Forest

Re: Rebuilt engine seized

Stuart Giles
Rather than use a reamer on slightly tight piston small ends where there's a risk of the reamer chattering in the softish alloy, I've found that using Flex Hone with a pistol grip drill does the job with a good finish. Flex-Hones are hugely cheaper bought from the USA (even once the international shipping is paid) than buying them here. http://www.ebay.com/itm/1-2-13mm-Flexhone-flex-hone-lifter-bore-240-grit-/351954884089?hash=item51f22555f9:g:SuQAAOSwZ8ZW6bq1&item=351954884089&vxp=mtr


Stuart - I am quite taken by the Flex-hone, thank you for sharing it.

I noticed a similar product from Gunson https://www.machinemart.co.uk/p/gunson-77075-3-piece-flexible-honing-brush-se/?da=1&TC=GS-040217775&gclid=CPui1pvDx9ECFUI6GwodHEAJcQ

I think however that I will save up for the real thing.

Re: Rebuilt engine seized

I too have had a new rebuilt engine seize on me and it was due to a tight pin in the piston. This engine turned easy on the handle and started only to seize on becoming warm. I put this down to expansion of the pin on becoming hot as the engine warmed. When stripped down I had to break the piston to remove the pin (piston shot anyway). I made sure the new piston was really free on the pin by using clean oil and diesel to free things up before re assembly. It has now been running now for months without a problem.

John Mason

Location: Nottinghamshire

Re: Rebuilt engine seized

A quick update.
The engine went back together without hitch, and took it for a run of about 15 miles without any problems.
Hopefully that is the end of my troubles.
Many thanks for your help.
Adrian.

Location: The New Forest

Re: Rebuilt engine seized

Well done Adrian - I hope everything is trouble free from now on!

Re: Rebuilt engine seized

John you must be in thanet, I live in hoath,you interested in sorting my ruby engine out ?

Location: canterbury kent

Re: Rebuilt engine seized

Andrew I have sent you an "E"Mail.
J

Location: As far east in Kent as you can get

Re: Rebuilt engine seized

Thanks John , have replied to your mail, andrew

Location: canterbury kent

Re: Rebuilt engine seized

hi adrian,

did you find out what caused the problem.

tony

Location: huncote on the pig

Re: Rebuilt engine seized

Not really Tony, the new gudgeon pin and piston were a good sliding fit and the conrod was straight and true. I can only assume either I assembled it dry or I mixed the pins up if they are supplied as a pair. I guess it could have been a bad part, we will never know.
Thanks again for your input.
Adrian.

Location: The New Forest

Re: Rebuilt engine seized

Did you by any chance fit the circlips as well as the clamping bolt.
If you did this MAY be the source of your problem.

Location: Bristol

Re: Rebuilt engine seized

Hello Ian
No, I didn't fit the circlips. Your mind plays strange tricks when you try and think back. I vaguely remember one of the pins was a little stiffer to insert through the conrod than the others. It could be possible that it pushed up a slight burr on the pin or pushed a sliver of metal into the piston bore. A little more care on assembly probably the order of the day.
Adrian.

Location: The New Forest