Piston broke.......

[John Liddle]

..... so am I mate, so am I.

Produced for submission in another place.



Piston broke by John Liddle, on Flickr

[ST-EOS]

That seem to have gone though some trauma John, it may make a handy paperweight

[Trev B]

A bit beyond it me thinks - the piston not the picture!

[Bill53]

Someone's made a right mess of that John, nice lighting though.

[ST-EOS]

Out of interest what caused the damage John?
Interesting sort of crown shaped rather than flat top piston.

[John Liddle]

Out of interest what caused the damage John?
Interesting sort of crown shaped rather than flat top piston.

The piston was in a 2.5 litre Daimler V8 which a pal & I had in our small dragster many years ago. The car was originally built by Mark Stratton and had a 6.5 litre blown engine (Chrysler I think). He sold the car, but kept the engine and the new owner, Dave Prior, fitted the Daimler. On one occasion Dave had to move the car between garages and in the absence of a trailer, drove it down Barnet High Street in London.


Metronome2.jpg

The normal Daimler piston is relatively low compression and more or less flat-topped. It turns out however that the 2.5 V8 was designed by the same chap who designed the engine for the Triumph Bonneville and there is some commonality between them. Whether the Bonneville was 1/4 of a V8, or the V8 was four Bonnevilles, I do not know.

Thus it is that Bonneville pistons (which have a pronounced raised hemisherical head) fit pretty well straight into the Daimler, with the proviso that you need to machine some space into the piston crown to allow for the fact that the valves are mounted at different angles in the cylinder head.

Our problem came when we were testing the engine (along the car park of the Recreational Society at the Atomic Weapons Research Establishment at Aldermaston) and at max revs (circa7,500 rpm) the valve springs went into resonance and started just floating around the valve stem instead of doing their job. As a result, the collets on one valve became dislodged and the valve fell down the hole into the cylinder bore and met the piston coming the other way at high speed.

The engine coughed a bit and then picked back up, but we noticed there was unburnt fuel coming out of one exhaust pipe and the horrible truth became apparent!

We did a lot of work to find and get rid of all the little bits of piston and valve which had been distributed around the inside of the block, had the bore lined, dressed up the head and fitted much stronger (double) valve springs. After that, all was well.

Glory Days!!!

[ST-EOS]

Thanks for the background John, I did wonder if it was valve/piston trauma.
the Dragster looks like it was made to look like Del Boys Reliant Robin

[John Liddle]

Thanks for the background John, I did wonder if it was valve/piston trauma.
the Dragster looks like it was made to look like Del Boys Reliant Robin

It was actually a special purpose lightweight Bond Bug (qv) body made by the Reliant Co. for Mark Stratton

[El Sid]

Great picture and fascinating background details.

Says a lot about the quality and standard of engineering that it kept running despite this level of damage...