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Hone v rebore
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trampintransit



Joined: 09 Aug 2010
Posts: 166
Location: Edinburgh

PostPosted: Mon May 21, 2018 2:29 pm    Post subject: Hone v rebore Reply with quote

AS Star Sapphire.....smoke from crank breather and rocker breather....engine sounds / runs fine. ... compression 160 or thereabouts on 1,3,4,5,6 but 120 on 2, oil down bore and it's uyp to 160 ...so ..it's a ring bore problem. I understand that the real answer is head off and look but in order to maintain a psitive outlook...what's the chances of getting awy with a hone in situ and new rings?
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alastairq



Joined: 14 Oct 2016
Posts: 1295
Location: East Yorkshire

PostPosted: Mon May 21, 2018 3:03 pm    Post subject: Reply with quote

It's all a case of..you won't know until you look?

I don't know whether this would 'work', but Lidl have been selling those wee cameras on flexi stalks, for inserting into places never seen before? [Also, various sorts on ebay? Endoscopes,Borescopes, Whateverscopes?

Might be worth one of those down the spark plug orifice?


Might be nothing more worrisome than busted rings?
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trampintransit



Joined: 09 Aug 2010
Posts: 166
Location: Edinburgh

PostPosted: Mon May 21, 2018 3:23 pm    Post subject: Reply with quote

The scope thing kinda doesn't get me anywhere though does it? Whatever happens I've got to take the head off?

I know I'm kind of answering my own questions here...

If it's a busted ring and I've already done a couple of hundred miles like that ..will I not have scored the bore?
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alastairq



Joined: 14 Oct 2016
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Location: East Yorkshire

PostPosted: Mon May 21, 2018 3:28 pm    Post subject: Reply with quote

Not necessarily.

The rings will have gaps in them anyway.

The camera thing can be inserted via spark plug holes....no need to lift the head at that point.
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trampintransit



Joined: 09 Aug 2010
Posts: 166
Location: Edinburgh

PostPosted: Mon May 21, 2018 3:29 pm    Post subject: Reply with quote

But WHATEVER I do , the head has to come off..I can't establish the real extent of the damage just with a scope can I? ..
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Minxy



Joined: 22 Sep 2010
Posts: 230
Location: West Northants

PostPosted: Mon May 21, 2018 4:05 pm    Post subject: Reply with quote

If you take the head off you won't see a fat lot in all honesty. You might have a cleaner piston from the blow-past but what then? Ultimately you will need to remove the piston to examine it and the rings, possibly remove the rings and slide them down the bores to measure the gaps. You will also need to measure the bores for ovalness. As I'm sure you are aware the Pistons need to be removed even for a honing.

In my previously life as a specialist motor repairer I always experienced poor results from honing and replacement of rings and my opinion I would prepare for a rebore and treat anything less as a bonus.
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ukdave2002



Joined: 23 Nov 2007
Posts: 3491
Location: South Cheshire

PostPosted: Mon May 21, 2018 4:08 pm    Post subject: Reply with quote

You could perform a leak down test, to asses whether the cylinder is sealing satisfactorily, but if the cylinders are not holding pressure, then the head will have to come off, and also to measure wear or any ovality in the bores.

Dave
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Rootes75



Joined: 30 Apr 2013
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Location: The Somerset Levels

PostPosted: Mon May 21, 2018 4:21 pm    Post subject: Reply with quote

Head off sounds about right but as Minxy says ideally that means removing the piston/rings too. A lot of work.
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petelang



Joined: 21 May 2009
Posts: 246
Location: Nottingham

PostPosted: Mon May 21, 2018 11:18 pm    Post subject: Reply with quote

It could be that there is a valve not completely seating that could give a lower reading.
It might also be the orientation of the ring gaps is increasing blow by.
As you say though, it's really got to come apart to do anything and confirm.
I have had an engine apart that had many broken rings and not a mark on any of the bores.
Also, if oils have not been regularly changed you could have rings gummed up and stuck in the grooves. You might be able to overcome that with an oil change and flushing oil or some additive treatments but it's pot luck.
Peter
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MVPeters



Joined: 28 Aug 2008
Posts: 679
Location: Northern MA, USA

PostPosted: Tue May 22, 2018 12:17 am    Post subject: Reply with quote

Does it smoke (much) from the exhaust tail-pipe?

I think I'd soak #2 cylinder with carb cleaner for a day or two & see if that frees off the rings.
Meanwhile, clean all the breather hoses & filters.
Then fresh 20/50 oil.
Then take it for a nice long run & see what you've got.

One thing I don't see mentioned very often is the use of a vacuum gauge to diagnose many engine problems. Inexpensive & straightforward to use - try this link, but there are plenty of others:

http://www.crankshaftcoalition.com/wiki/Vacuum_gauge_engine_diagnosis
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Rootes75



Joined: 30 Apr 2013
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Location: The Somerset Levels

PostPosted: Tue May 22, 2018 8:25 am    Post subject: Reply with quote

That's a good interesting link.
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peter scott



Joined: 18 Dec 2007
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Location: Edinburgh

PostPosted: Tue May 22, 2018 10:16 am    Post subject: Reply with quote

Rather than disturbing the head you could possibly take the sump off and withdraw the piston downwards. It all depends on whether it's possible to get the piston past the crank. Even though the crankcase is a confined space it is sometimes possible to get a piston out by rotating the crank and keeping the piston with the crank as you rotate it.

It is easier if you only have 4 main bearings (which I think is the case with your engine) but I have managed it with my 7 bearing SS Jaguar.

Peter
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MikeEdwards



Joined: 25 May 2011
Posts: 1869
Location: South Cheshire

PostPosted: Tue May 22, 2018 10:22 am    Post subject: Reply with quote

alastairq wrote:
I don't know whether this would 'work', but Lidl have been selling those wee cameras on flexi stalks, for inserting into places never seen before? [Also, various sorts on ebay? Endoscopes,Borescopes, Whateverscopes?


Off-topic I've got an eBay one. The camera might be OK, but the software for displaying the image is rubbish, locking up every few seconds and needing to be restarted. Probably what I should expect for the money.
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jp928



Joined: 07 Jun 2016
Posts: 247
Location: Australia

PostPosted: Wed May 23, 2018 9:17 am    Post subject: Reply with quote

A leakdown test is best way to diagnose where the problem is. Basically, remove dipstick, air cleaner, any PCV valves; get sylinder on TDC firing (valves closed), in gear so engine cant rotate, apply air pressure through spark plug hole. If you can hear air escaping from air inlet, its an inlet valve; if from dipstick or PCV valve, its rings; if out exhaust pipe, its an exhaust valve. I havent done it myself, but have been told its quite easy to hear any air leaks. Now that you already know which cylinder is down on comppression, you know where to start, and do one other cylinder as a comparison.
jp 26 Rover 9
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trampintransit



Joined: 09 Aug 2010
Posts: 166
Location: Edinburgh

PostPosted: Wed May 23, 2018 10:47 am    Post subject: Reply with quote

Blimey...that kicked off didn't it! Lots to think about...but to some extent I already know some of the answers. the fact that putting oil down the bores immediately puts the cylinder back up to 160 as per all the others pretty much confirms it's not a valve. Iterestingly, it's the hassle of taking the head off that I assumed was unavoidable ( apart from anything else it's a muckle head ...I've seen one off a car and believe me ..I've MOT'd things that weigh less than that head! )

BUT ..the most interesting thing here is the idea that maybe the pistons might come out down the way? Didn't think about that!1 But surely getting the damn things back in would be tricky as hell wouldn't it?
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