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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Mon Jan 26, 2009 5:07 pm    Post subject: stuck Reply with quote

Hello all

Generally cleaning pistons, rods and caps etc today ready for replacement. I am changing conrod bearings and main bearings while I'm at it. I have a small problem with the assembly pictured in that the pin is stuck in the piston in that position. It is currently soaking in WD40. I only removed these a couple of weeks ago and the engine tuned by hand quite freely. If lubricant doesn't do the trick is it worth trying some gentle heat although I have to admit to doing this on an aluminum piston doesn't appeal to me.

What are your opinions about changing the rings while I am here? They look OK to me!
Any suggestion gratefully accepted.

Thanks
Brian


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47p2



Joined: 24 Nov 2007
Posts: 2002
Location: Glasgow

PostPosted: Mon Jan 26, 2009 7:01 pm    Post subject: Reply with quote

I would think if it is seized to that extent then I would be removing it to inspect for the cause and any damage before a rebuild.

Easier to fix it now rather than later
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peter scott



Joined: 18 Dec 2007
Posts: 6221
Location: Edinburgh

PostPosted: Mon Jan 26, 2009 7:18 pm    Post subject: Reply with quote

The gudgeon pins are normally only a push fit at elevated temperature.

I think you'll find things much easier if you just put them in a bucket of boiling water for five minutes then get someone to hold the piston in gloved hands whilst you hit the pin with a heavy hammer via a suitable sized socket on a 6 inch extension. Give it sharp but controlled blows. Clearly you don't want to knock it out of your assistant's hand.

I just did the same job a few days ago but found that just sitting the pistons in front of a fan heater was sufficient and no assistant was required.

The rings should be fine. Just adjust the gaps to be oriented apart from each other when you re-assemble. Assuming none is broken then you have nothing to gain by changing them. If you do have to change any then you will need to use a glaze busting tool on the relevant bore or the new rings will take a very very long time to bed in.

Actually, reading your post again it's not clear to me whether the conrod is stuck on the pin. If so then it might be worth applying a very small oxy-acetylene flame to the small end of the conrod. The pin should be fairly solid in the piston. Try puting the piston in a bore of your block and apply some torque on the rod.

Peter
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Mon Jan 26, 2009 8:09 pm    Post subject: Reply with quote

Ok thanks chaps

Sorry Peter it's the pin that is stuck but that obviously in turn seizes the rod until the pinch bolt is undone.

The hot water worked a treat! Loosened up enough to move the conrod and managed to knock the gudgeon the few millimeters from the side of the piston. But as it cools it is becoming stiff again. I've orientated the conrod so as I can now undo the pinch bolt. Is it just a case of knocking the pin straight out to see why it is so stiff?

Re the rings. In my ham fisted way I have managed to break one of the oil rings. What is precisely does a glaze busting tool look like and how is it used?
OK now found one. Three legged affair that fits a drill or the like.

Brian
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peter scott



Joined: 18 Dec 2007
Posts: 6221
Location: Edinburgh

PostPosted: Mon Jan 26, 2009 9:11 pm    Post subject: Reply with quote

Hi Brian,

I'm glad things worked with the heat.

Yes, cast iron rings are incredibly delicate and especially the ones with gaps in them. You want to have a sort of criss cross pattern of small scratches spiralling down the bores. You can do it by hand but the tool makes it very much quicker and easier.

Peter
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peter scott



Joined: 18 Dec 2007
Posts: 6221
Location: Edinburgh

PostPosted: Tue Jan 27, 2009 2:32 pm    Post subject: Reply with quote

Another thought... With the need to bed in new rings don't run your engine on synthetic oil for the first 1000 miles, buy the cheapest 20W50 you can find
and only put in decent oil thereafter.

Peter
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Tue Jan 27, 2009 5:49 pm    Post subject: Reply with quote

Blast!! Nothing is ever easy!
As I mentioned the pin started to seize again after cooling but I had orientated the conrod so I had better access to the pinch bolt. Carefully holding the conrod in a vice, with plenty of protection the bolt was very tight, slowly undone then broke!!!
What to do? I remembered I had a heat gun so applied heat until the pin freed up again and the proceeded to knock it through. It came out with a bit of a struggle but as it went through it scored itself against the broken half of the bolt, picked up and in turn scored the piston bore. Arse!
Thought I might be able to ream the piston again and buy a new gudeon pin. Rang around and got wildly differing quotes. Can't buy a pin without the piston. Haven't got +.030 only standard. Can't split a set! Anyway upshot is I had to buy a full set of NOS pistons,complete with pins and rings.
I still have to remove the broken bolt from the small end and definitely buy a deglazing tool!!
Feel like I've played my part bailing out the UK auto industry today!
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peter scott



Joined: 18 Dec 2007
Posts: 6221
Location: Edinburgh

PostPosted: Tue Jan 27, 2009 7:43 pm    Post subject: Reply with quote

Hi Brian,

Sorry to hear of your further troubles. Your "Nothing is ever easy" message rings very true for me too if you've seen my recent odyssey. Crying or Very sad

You weren't conned (sorry about the pun) with the pistons. Pins are normally only standard size.

Well done though on your single-handed support for the industry.

With these clamped gudgeon pins the pin is meant to revolve in the piston but you can expect them to be tight at room temperature. Looking at the Austin Sheerline specs it says "thumb push at 70F".

Peter
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Tue Jan 27, 2009 8:08 pm    Post subject: Reply with quote

Hi Peter

All the other pins move freely in their respective pistons but not too loose or slack in any way. I cannot find any unwanted movement. However this piston in particular was in my opinion far too tight and certainly not how my sheerline handbook shows the pin to be, a short of push fit with your thumb.

No I didn't think I was conned at all. In the end it was not a bad deal really and I'm happy knowing that it'll be a good rebuild. And I've loads of spares!

Oh, and I've read your threads. Why on earth do we do it!

Brian
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ukdave2002



Joined: 23 Nov 2007
Posts: 3522
Location: South Cheshire

PostPosted: Wed Jan 28, 2009 11:24 pm    Post subject: Reply with quote

Hi Brian

I rebuilt a Morris 8 engine a couple of months ago, it had NOS rods pistons and pins, 3 of the pins pushed in fine, one too a bit more force and was very stiff, I ended up running a reamer through the piston, there must have been a tight spot, and it was then all ok, I wouldn't think the pins will get much oil in a running engine so a tight one may well give future problems...
Dave
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Thu Jan 29, 2009 5:33 pm    Post subject: Reply with quote

Hi Dave

Looking at the gudgeon pin now it is out, there is clearly some pick up in both spots around that would be in contact with the piston. Due to this fact I'm glad I did investigate further because as you have said it would almost certainly cause problems at some stage and for nothing else but peace of mind. I have managed to get the broken pinch bolt from the small end out successfully without damaging the thread so that's a bonus!

New pistons arrive tomorrow hopefully so things can start going back soon. At least it takes you're mind off the depressing state of the economy!

Brian
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Kelsham



Joined: 18 Jan 2009
Posts: 349
Location: Llandrindod Wells Powys

PostPosted: Fri Jan 30, 2009 2:58 pm    Post subject: Piston rings Reply with quote

Dont forget to remove the rings from your new pistons and enter them into the bore to check you have the correc t ring gap.
I recently fitted new rings to my Morris Landcrab and found they were too tight. regards Kels
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Fri Jan 30, 2009 8:05 pm    Post subject: Reply with quote

Cheers Kels

The gap from the Sheerline book gives .011" - .015" for 'the rings' but doesn't differenciate between compression rings or oil rings.

I have double checked using the formula bore diameter, 3.4375 x .004" for comp rings = .01375" which is in tolerance.

and bore diameter 3.4375" x .005" = .01718" for oil rings, which is out of tolerance.

unsure what way to go with that. I assume the rings are easy to file if too tight?

Regards
Brian
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peter scott



Joined: 18 Dec 2007
Posts: 6221
Location: Edinburgh

PostPosted: Sat Jan 31, 2009 5:53 pm    Post subject: Reply with quote

Just to add to the confusion The Motor Trader does separately quote gaps for compression and oil control rings but both are 8 to 12 thou.

Peter
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