Thornycroft T80 Rebuild or not???????

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rich201283

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I have a Thornycroft T80 with a shattered piston, It looks like the gudgeon pin has shattered. I have looked at the other cylinders and 1 of the other gudgeon pins is cracked, What could have caused this? I have spoken to a engine builder and he rekons these engines are designed to be thrown away not rebuilt. Am i better off re-building this engine or putting a 1.5 bmc in?
 
take a lok at the pin note the colour
it does sound like as others have said head gasket failed heated up head distorts causing gasket to fail letting water in hence the major damage
the whole engine has to be stripped to clear any debri from the oil ways sump and so on
I'd be thinking the crankshaft may be damaged as well

Might be as well to compare costs of another engine especially if heads cracked or to badly warped same re block, there is only so much that can be skimmed off a head

cheers
Mick
 
What sort of "engine builder" is he, throwaway? sounds more like a "box" shifter to me.
Have a look at www.asap-supplies.com for the price of bits. Be aware that it sounds pretty catstrophic, question, have you seen the damage or are you relying on the engine builder for info?
Stu
 
Yes i have stripped the engine today, i found the crown of the piston intact and the skirt in bits, also the gudging pin in bits, however the con rod appears ok and has one mark on it.

I thought i would check all pistons and gudging pins and found another which had split.

Although all bores look in good condition, even the one with the piston damage, what i can see is that there are marks where all four gudging pins have moved and marked the bores lightly, strange because they are not designed to have circlips, anyone seen this idea before?
 
They used to do tight fit gudgeon pins in vauxhalls years ago, no circlips, if they have moved then its got very hot as has been posted by others. if the pin has scored the bores then end of game, if they have just marked them then maybe a light hone will fix it. Prob is a set of pistons will cost in hundreds of pounds, gasket set the same, and so it goes on. You need to post some pics for us to give an opinion.
Stu
 
Err.......not perhaps? I've got a Thorneycroft 1.8 BMC in my Ocean 30 ex-hire. It is as good after probably 40 odd years as a hire boat as when it went in although probably the hire fleet owners could have rebuilt it
I suppose.

However, to the point, most Thorneycroft engines are marinised car lumps they told me, mine, it might be the T80, I'm not sure, is the same lump as in the old Sherpa van and you can still get those engines in reasonable nick in the scrappie yards. If your is the same I suggest you get hold of one and swap all your bits across and scrap the old unit.

Like the other poster says, talk to Thorneycroft, I find them really helpful. Tel. no. is 01772 611144 and fax no. is 01772 616364. Good luck.
 
The T80 is one of the modern thornycrofts based on Mitsubushi engines, if you want and older one the T90 is the one based on the BMC 1.5. They turn up from time to time usually for less than £1000, but Thornycroft do a part exchange scheme.
 
Have just seen your post. If the gudgeon pins (note spelling) are this damaged I would agree that the engine has overheated (coolant failure?) and the pistons have partially siezed causing over stressing. For the pins to have moved in the piston it is clear that overheating has indeed taken place. If you have had the pins hit the cylinder wall you wont get this out by light honing which is only designed to bust the glaze. I would suggest that you need to strip the whole engine, check the big end bearings and shells, have it rebored and fit oversize pistons at least. You should also check that all coolant passages are clear and the heat exchanger is not blocked as this is the most common cause of overheating. Is it worth it? Well if you are confident to do the work yourself it really depends on the cost of pistons, rings, gaskets, and main bearings (assuming these are shot too) Check with Mitsubishi agents and auto spares places (like autopart) before making a decision but I would think just fitting new pistons without a rebore would be a false economy. If its not too old and the head and other bits are in good nick I would think a rebuild is economically viable. I would forget second hand engines unless you know precisely where they have been. You might well buy more trouble.
 
Leer,

Boatmike is pretty much on. Gudgeon pin (properly known as the wrist pin) has blued indicating oil starvation. The lube pressure path is from pump, then to mains, big end finally small end which is at the end of the food chain. However this is all sematics, as small Japanese engines of any flavor although feasable to rebuild are rarely practical. Very reliable and durable but never cost effective for the individual to rebuild.

Going back to clunking old BMC is not the answer either.

Getting Thornycroft involved is just another mouth in the food chain as they purchase their base engines from Diamond Diesels the Mitsubishi U.K. agent who have a far better handle on the product than Thornycroft.

Suggest you find out Diamond Diesels have, perhaps a long motor to hang your marinising bits on. http://www.diamonddiesels.co.uk/marine.htm
 
Agree absolutely.... interesting link to Diamond too. I have a Vetus 4 cylinder based on Mitsubishi. Never required spares for it but seems Diamond might be useful if I ever do....
 
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