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Hone v rebore
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alanb



Joined: 10 Sep 2012
Posts: 431
Location: Berkshire.

PostPosted: Wed May 23, 2018 11:11 am    Post subject: Reply with quote

Not really any more difficult than from the top though a ring compression tool is a must, plenty of older cars with long stroke small bore engines the pistons had to be removed from the bottom as the conrod big end was larger than the bore, the 803cc version of the A series engine was one I believe. Anyway Good luck with whatever needs doing.
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Penman



Joined: 23 Nov 2007
Posts: 4129
Location: Lancashire

PostPosted: Wed May 23, 2018 12:16 pm    Post subject: Reply with quote

Hi


Just make sure the valves on that cylinder aren't both closed when withdrawing or inserting piston.
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Bristols should always come in pairs.

Any 2 from:-
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jp928



Joined: 07 Jun 2016
Posts: 247
Location: Australia

PostPosted: Wed May 23, 2018 1:47 pm    Post subject: Reply with quote

Yes it would be difficult to get back in from underneath - how would you compress the rings? A small home made strip that you tightened with a jubilee clip might do it. Modern engine assemblies I have seen on youtube use a tailored plastic item, like a funnel with a VERY light taper, which probably engages in a tiny shamfer at the top of the bore - drop the piston and rod assembly into it, sit it over the bore, smack the piston with a mallet, all over.
A home leakdown test would at least confirm the ring diagnosis. And you have to take the sump off wither way, so you might see if bottom removal is possible.
jp 26 Rover 9
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peter scott



Joined: 18 Dec 2007
Posts: 6179
Location: Edinburgh

PostPosted: Wed May 23, 2018 8:26 pm    Post subject: Reply with quote

I was not able to get a ring compressor into the space on my engine but as with most engines the bottom of the cylinders have a chamfered entry. Carefully compressing each ring with a screwdriver I did manage to get them all in although it wasn't easy.

Peter
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Penman



Joined: 23 Nov 2007
Posts: 4129
Location: Lancashire

PostPosted: Wed May 23, 2018 9:13 pm    Post subject: Reply with quote

Hi There are some engines which don't have clearance for the pistons to pass the crankshaft.
These can sometimes be identified by the big end journals being divided on an angle thus allowing the top of the journal to pass up through the bore.
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Bristols should always come in pairs.

Any 2 from:-
Straight 6
V8 V10
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peter scott



Joined: 18 Dec 2007
Posts: 6179
Location: Edinburgh

PostPosted: Wed May 23, 2018 9:38 pm    Post subject: Reply with quote

I really only suggested removing the piston downwards because it saves disturbing the head.

The angled big ends can be a real pain as I discovered when trying to unseize a Wolseley 6-80 engine that had lain full of water for years. With all the pistons locked into their bores it was essential to disconnect the big ends so that each cylinder could be tackled separately rather than trying to free all six at once. Unfortunately the angled big end bolts that were high up in the block were inaccessible to any socket and also to the normal offset ring spanners.

Although not relevant, trying to remove the head proved equally challenging because you needed to remove the overhead camshaft to access the head nuts but the camshaft journals are not split so it needs to be withdrawn lengthwise. There are special tools to compress all the valves simultaneously to facilitate shaft withdrawal but I'll bet the designer didn't recon on every valve being seized in its valve guide!

The 6-80 engine looks quite nice on the drawing board but it's pretty gutless on the road and a nightmare to work on.

Peter Twisted Evil
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Kleftiwallah



Joined: 27 Oct 2016
Posts: 222
Location: North Wiltshire

PostPosted: Thu May 24, 2018 6:12 pm    Post subject: Reply with quote

I've used this bit o' kit quite often when peering into "Crooks and Nannies" on various H.M.t.Q's aircraft.

I've always known it as a 'SHUFTISCOPE' !

Surprised

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