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help needed....piston related
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Jason



Joined: 12 Nov 2008
Posts: 623
Location: Todmorden, Lancs.

PostPosted: Tue Aug 12, 2014 4:33 pm    Post subject: help needed....piston related Reply with quote

I've had some issues with the crankcase pressurising and spitting oil out through the crankcase breather pipe, so today I've began stripping the engine to see whats what.....pics later.

its an Alvis TA14 4 cylinder and after removing the pistons to check the bores and rings....
the bores are glazed and the rings are clean.

there is no sign of a wear lip at the top of the bores, they're just badly glazed / shiny.

now this is where I need a bit of help.....
the pistons are stamped '+0.30' so it has been bored or honed out before.
(the original bore was 74mm)

Do I hone the glazed bores and fit new rings?, if so what size rings? and where do I get them from, I've spoken to red triangle (Alvis agents) and they are unable to help.

Or could I hone the cylinders and reuse the old rings ?

Or do I send the lot to a engine builders and get them to do it?

I'd prefer to reuse my old pistons as there is no sign of any wear or damage.

any help on this matter would be great
thanks in advance
jason
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Phil - Nottingham



Joined: 01 Jan 2008
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Location: Nottingham

PostPosted: Tue Aug 12, 2014 6:10 pm    Post subject: Reply with quote

Thorntons will have the new pistons - find out the cost and weigh up with the use you want out of it. That will clarify your questions
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V8 Nutter



Joined: 27 Aug 2012
Posts: 587

PostPosted: Tue Aug 12, 2014 8:06 pm    Post subject: Reply with quote

If the bores are in tolerance, a light honing just to break the glaze and probably a new set of rings should sort out your problems. When the engine is running again don't leave it idling for any length of time, the bores will just glaze up again. Take it out on the road as soon as you can.
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Tue Aug 12, 2014 9:27 pm    Post subject: Reply with quote

If your rings are intact I wouldn't bother to replace them. Glaze busting possibly since you're in there. Breather design is sometimes not that good at preventing splash from exiting. Check to see if you can improve things with a suitable baffle.

Peter
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Jason



Joined: 12 Nov 2008
Posts: 623
Location: Todmorden, Lancs.

PostPosted: Wed Aug 13, 2014 5:06 am    Post subject: Reply with quote

thanks for the replies

Phil, I've emailed Thorntons to see what stock they have and cost

Peter, the rings are intact and look in good condition, I have a honing tool with various grit stones....which grit would be best for glaze busting?
pardon my ignorance, but whats a baffle?

jason
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ka



Joined: 03 Dec 2007
Posts: 600
Location: Orkney.

PostPosted: Wed Aug 13, 2014 6:35 am    Post subject: Reply with quote

Use the finest grit, you are just trying to break up the shine, although in my view, if you are not putting new rings on, leave things alone, a mirror finish on the bores is what we should strive for, this gives maximum compression, whilst the cast iron and micro holes retain oil to lubricate.
A baffle is something that stops direct access. In this circumstance, I think there are two ways to go, a baffle made of a ball of wire, so it looks something like those shiny aluminium look scouring pads, this allows air/gasses to flow easily, whilst trapping oil to allow this to run down into the engine, plan 'b', is to extend the breather to above/level with the rocker cover, this means that gravity will reduce the oil flow, then catch the residue in a beer can, chosen to suit liking, but always promotes a conversation. (I use Ruddles County)
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peter scott



Joined: 18 Dec 2007
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Location: Edinburgh

PostPosted: Wed Aug 13, 2014 8:09 am    Post subject: Reply with quote

Jason wrote:
, but whats a baffle?

jason


I was just thinking of a metal plate that prevents splashes going straight down the breather pipe but still leaving a gap around the edges where air/gasses can pass unimpeded.

Peter
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V8 Nutter



Joined: 27 Aug 2012
Posts: 587

PostPosted: Wed Aug 13, 2014 7:44 pm    Post subject: Reply with quote

I have to disagree with with Ka on bore finish. You should be aiming for a cross hatch honing pattern. Too smooth a finish the rings will never bed in and you will have an oil burner.

The old Van Norman portable boring bars produced a finish with very slight pits that supposedly did not need honing, but when I worked in the engine reconditioners we allways honed for finish. First with fine stones, then with cork sticks with gave the optimum plateau honing finish.
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PAUL BEAUMONT



Joined: 27 Nov 2007
Posts: 1281
Location: Barnsley S. Yorks

PostPosted: Thu Aug 14, 2014 1:00 pm    Post subject: Reply with quote

I entrust this sort of stuff to a proper engine reconditioner. I know it is a bit of a leg for you but I highly recommend Bland's in Barnsley. I have no association with them, but they have done some first class work for me.

Paul
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ka



Joined: 03 Dec 2007
Posts: 600
Location: Orkney.

PostPosted: Fri Aug 15, 2014 7:06 am    Post subject: Reply with quote

I have no issue with V8 comments, if you are fitting new rings, hone, if not leave well alone.
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KA

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Jason



Joined: 12 Nov 2008
Posts: 623
Location: Todmorden, Lancs.

PostPosted: Sat Aug 16, 2014 11:00 am    Post subject: Reply with quote

I've decided to remove the engine and rebuild the lot.....new rings, bearings, seals etc etc.....so I will be honing it out.

and whilst its in bits, I'm going to get the clutch relined as well....


I've just got the engine out, so after a brew, a complete strip down will be on the agenda for today...... I'll post some photos tonight.
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Jason



Joined: 12 Nov 2008
Posts: 623
Location: Todmorden, Lancs.

PostPosted: Sat Aug 16, 2014 7:06 pm    Post subject: Reply with quote

photo's will appear here shortly.....
http://www.oldclassiccar.co.uk/forum/phpbb/phpBB2/viewtopic.php?p=120420#120420
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