What the heck has happened now (photos attached)

[Simon Jones]

Bear in mind it's run fine for nearly 1000Km, so unless the timing belt jumped a cog (or snapped), then it is unlikely to be an assembly issue. Another option is a valve spring has broken so the valve did not return fully into it's seat.

[timorr]

Here is a little more info on its last day that might add some interest.

It started running with a heavy chug (shaky and loud on low reeves but seemed to smooth out with a bit of reeves) and giving out white smoke or steam.
I was about 2 miles from home. The journey back was very sluggish on power. Got home and left it for the night.
Next day started it up, same heavy chug and smoke. Let it run for a few minutes no change and no rise in temperature.
Decided I would be able to drive it down to my local garage less than a mile away (not the garage that did the work).
After about 500m of driving, big puff of smoke a bit like a back fire, and then the engine was running smooth as ever. Full power back, normal sweet sound to engine and no smoke. Went on to the garage which was closed.

As everything was running smooth and all seemed normal, I decided that I should get it to the original garage that did the work which was about 250km away. Rang the garage first and explained the problem. They seemed to think it would be fine as long as the smoke and noise stayed away and the temperature stayed down.

After about 240km the engine started to chug again, but no smoke. Temperature normal but power lessened. I drove about another kilometer like this when suddenly the noise became like a cement block in a washing machine. Pulled right over into the hard shoulder in a panic as I though the whole thing was on fire with the amount of what i thought was smoke, but obviously turned out to be steam.
And then that was it...garage came out the last 9km and carried it home, opened it up and the photos tell the rest...or do they????

[dandywarhol]

Where do you see TWO damaged valved allidelta?

Have you checked the glow plug on that cylinder yet?

[AlliDelta]

Where do you see TWO damaged valved allidelta?

I may have got confused but thought the poster had said a couple were bust...

[dobby]

Gutted for you mate

The photo only shows the underside of the head so assuming it was assemble correctly, it must be component failure.

I guess you need to speak to the supplier but I would consider an engineers report asap to accurately record what has been discovered and then offer opinion. May even advise on legal action? Hopefully the supplier will be helpful?

An option would be to buy and a second-hand engine for now if funds(visa) will stretch and then once the row of the head is resolved either refit the rebuilt original and sell the old engine or get a full refund on all parts?


Hope it all works out

[The Great Pretender]

i know nothing me but, in pic 1 of the head it looks to me like the area betwwen the valves has got really hot and melted towards the piston/chamber,this has damaged the seat,and snapped the valve.
looks like the heat came first then the damage was done.
like i say-----i know nowt me, .

After enlarging the photo I think you hit the nail on the head.
My theory is that the casting was faulty. I could be totally wrong BUT............ There is or should be a waterway there above the chamber. So if there was coolant there it shouldn't have melted.



Circled is the waterway above the position that it melted. If there was a problem when casting (I don't want to go into how the hollow parts are cast) that isolated the highlighted portion from the cooling system you would have a sealed pocket. As the metal here is at its thinnest (expecting the coolant to remove the heat) you have an expanding superheated pocket of air ready to blast out as soon as the alloy reaches a soft state, hence the eruption.
This may have happened before the problem became terminal.
The valve seat could have at first been compromised allowing 'steam' that was unburnt fuel due to lack of compression causing the original problem.
Valve stems can become soft and it is possible it was trying to seal on the second journey before it cried ENOUGH and snapped. As that cylinder is then dumping unburnt fuel into the exhaust you get 'steam' or white smoke.

How would I test this head to try to prove my theory?....................Simpeeeeeels
I would trickle water into the eruption, if it didn't run out or just dribbled out, problem solved.
No need for an engineers report, just get the head cut in half across the centre of the problem. Steve Widdowson did it.It's his cut out pic that I posted.
I may have got it wrong so feel free to shoot me down guys.

[timorr]

So...anyone interested in an update.

Waiting to hear back from the part suppliers now. They have all the photos as well as the ones below of the other side. Anyone got any more thoughts on what happened?

[scanner]

Valve retaining collett popped out and allowed valve to drop?

I.E. whoever installed the valve didn't make sure the colletts were seated properly ?

[321Away]

Valve retaining collett popped out and allowed valve to drop?

I.E. whoever installed the valve didn't make sure the colletts were seated properly ?

Where was the stem of the valve found? even without the head of the valve, the stem shouldnt be able to drop as spring pressure would just push it against the cam? assuming thats the scrubbing on the cam lobe in the picture and the mishapen valve guide?

Julian

[widdowson2008]

Can you check the tightness of the spherical seat (rocker seat) opposite this valve?
Reason for asking is that when we fitted a new head recently, we had a note through the post 24 hours after the head was delivered, to check the tightness because 'some' had been delivered in an 'unset' state.
If it IS incorrectly set, could this unscrew itself gradually? and in doing so, effectively cause the valve to work progressively lower in the cylinder bore and eventually smack the piston (and smash its head off)?
Have a read through this topic and see if any applies to you.
http://www.igmaynard.co.uk/bongo/forum/ ... =3&t=50086

[rita]

Valve retaining collett popped out and allowed valve to drop?I.E. whoever installed the valve didn't make sure the colletts were seated properly ?

[dandywarhol]

Valve retaining collett popped out and allowed valve to drop?I.E. whoever installed the valve didn't make sure the colletts were seated properly ?

Second that - were the collets and spring retainer still lying in the cam cover?

Collet has sprung out, valve dropped, piston had smashed into the dropped valve and cleaved the valve head off........IMO

[Velocette]

There have been cases on here where built up heads have been supplied with incorrect valve clearances and or loose parts. Did the garage check this? I believe a tight valve clearance can cause this sort of damage.

If this is bollocks, sorry I am surmising what I have seen on here and my experience of petrol engines!

[widdowson2008]

There have been cases on here where built up heads have been supplied with incorrect valve clearances and or loose parts. Did the garage check this? I believe a tight valve clearance can cause this sort of damage.

If this is bollocks, sorry I am surmising what I have seen on here and my experience of petrol engines!

No - aint a load of bollocks - see the link a few post ago.
We stripped the head back to get at the 'possibly' loose bits only to find they had been correctly torqued. However, the supplier was concerned enough to tell us to check.

[rita]

Valve retaining collett popped out and allowed valve to drop?I.E. whoever installed the valve didn't make sure the colletts were seated properly ?

Second that - were the collets and spring retainer still lying in the cam cover?

Collet has sprung out, valve dropped, piston had smashed into the dropped valve and cleaved the valve head off........IMO

That was the last thing that we done after fitting/springs/caps and collets...............Gave the top of the valve stem a Great Wallop with a 2lb hammer.