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ghostlymoron

ghostlymoron

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I'm in the process of re building a Volvo Penta MD1. I've removed the head which looks in surpringly good condition but there are some carbon deposits to be removed. Is there some solvent that can be used or should I just wire brush it and then lap the valves in.
Is it worth honing the bore while its apart and is this a DIY job?
 
I've always just used white spirit or paraffin or whatever to soften the carbon and then scrapers, wirebrushes etc to remove it.

Honing is possible with the right equipment but I reckon you would need to remove the block.

If there was no problem with compression or running it's probably not worth the extra work.

Richard
 
leave a small amount of carbon around the circumference of the pistons. If you clean it all off you may lose compression. Mine did - and the resolution was quite tricky.
 
Not a rebore . But I had to introduce engine oil into the combustion chambers to provide some initial compression at start up. As there were no heater plugs, the oil had to go in through the injector holes which meant bleeding the system before starting was attempted.
 
tjbrace said:
Not a rebore . But I had to introduce engine oil into the combustion chambers to provide some initial compression at start up. As there were no heater plugs, the oil had to go in through the injector holes which meant bleeding the system before starting was attempted.
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Surely the rings should have been oiled when you put the thing together?
 
No. Head off, valves ground, injectors sent away for service. To my mind the rings were untouched so still lubricated. This was 1996,the engine was from1981. Three further owners later and the engine and boat are still in regular use. I think my fix was ok.
 
ghostlymoron said:
I'm in the process of re building a Volvo Penta MD1. I've removed the head which looks in surpringly good condition but there are some carbon deposits to be removed. Is there some solvent that can be used or should I just wire brush it and then lap the valves in.
Is it worth honing the bore while its apart and is this a DIY job?
Click to expand...

I'm surprised by the lack of responses to this thread so I presume these engines normally go on and on forever?
I've no experience of marine engines but generally, I would use wire brush attachments on an electric drill to remove the carbon from the head including the ports. Be careful around the valve guides and a compressor is useful for blowing away the mess. I have a bench grinder with wire wheel for removing the carbon from back of the valve heads and stems.
I agree with not removing the carbon from the piston(s) but then you don't want to leave heavy deposits which could glow and cause ignition problems.

There is honing and there is glaze busting. Glaze busting is honing, but just a tickle, where honing is about removing material. If the bore has become highly polished it may be worth glaze busting: a quick up and downer with honing stones in an electric drill. It'll produce a less shiny surface and emphasise any "lip" at the top of the bore not swept by the top ring. Too much glaze busting will remove too much material and could cause piston slap so be careful. There should be something on Youtube I would think.

I hope some of this helps.
 
Many years ago there was a local machine shop - literally a high street shop - run by a very experienced guy. Being a mechanical inspector, I had miced up the bores of my Triumph 500cc engine and decided it was rebore time. Looking at my figures and the bores he said he could get me at least five years use by glaze busting and fitting 0.010 o/s rings with the ends ground to the correct gap. As that amounted to a quarter of the cost I went for it, but asked about the ridge and the top ring. He was using a stepped top ring to increase the clearance. As far as I know the bike is still running like that, though it is a fair weather machine nowadays.

I wonder whether such specialised people and repair parts are still around? The business went to the dogs when the old guy died and his son took over. He'd never come up to his dad's standards whilst he was alive. Dad liked a fine tolerance challenge, son liked it easy.

Rob.

P.S. Marine engines tend to run too cold and if left unused it is not unusual for the rings to get stuck in their grooves so they don't seal. A little oil to improve compression for the first start and then the thermal cycling sorts them out.
 
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I've now taken the barrel off and examined briefly the piston and rings. The rings seem a bit stuck in their grooves but I'm reluctant to remove them for fear of breaking them and not being able to get replacements.
 
It may be possible to free the rings off simply by squeezing them and wriggling them. I'd suggest you squirt some WD40 or similar into the grooves whilst you're working at them to keep them lubricated and hopefully flush out the gunge. Lube them with engine oil once you've finished, though. Don't forget the rings are excellent scrapers and the piston is only ally!

Rob.
 
rob2 said:
It may be possible to free the rings off simply by squeezing them and wriggling them. I'd suggest you squirt some WD40 or similar into the grooves whilst you're working at them to keep them lubricated and hopefully flush out the gunge. Lube them with engine oil once you've finished, though. Don't forget the rings are excellent scrapers and the piston is only ally!

Rob.
Click to expand...

+1
If you have time, give them a good squirt and retire for a bit while it penetrates, then wriggle.
 
When I removed my engine block there were two areas of concern regarding re-assembly first was to obtain the correct lower shim gasket thickness which determines the compression ratio and clearances. I also found it difficult to secure the feed that is screwed into the lower base and lubricates the valve gear. The main difficulty was supporting the block weight whilst tightening the connection with little room for a helper to avoid shim s being damaged here.
I used Keyparts for my spares who sent me lists of current MD1 items. new piston rings came from a German source I think.

Good luck!

ianat182
 
Ianat, I've got a VP head gasket and bottom gasket but will have to make some of the others. A set of piston rings is over £100 so I'm not going to change them. AFAIK compression was OK but it was seized up. It's free enough now so probably just corrosion twixt piston and barrel.
 
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