K series let go

[Wrightpayne]

I think Stu is right - you need to sort out the oil system. The apollo was a reasonable upgrade for academy cars on standard power sealed engines. More power and more cornering G force, especially with grippy tyres, I’m not convinced its enough.

If you cannot afford the dey sump system I’d be inclined to use standard spec engines and just enjoy the power thats available. A friend with an R500K said my 1.6 supersport K was nearly as enjoyable to drive at Cadwell as all the power was useable and also made you drive better/neater to maintain momentum.

Just my 0.02p worth!

Ian

[rj]

I revved Trophy pistons to 7k85 for ages without issues.

Car is mainly used for trackdays and until this year was on wet sump and apollo. Bearings are fine after 23k km whatever that is in miles; following a broken cambelt the rest less so :-p

[p.mole1]

Thanks, engine is out and apart.It doesn't look like oil starvation, although number 2 rod has spun a bearing, possibly a rod bolt failure or the bolt has lost it's clamping load?

The main bearings have the most wear, one thing I have noticed is the bearings are a sloppy fit in the rods the bearing tang seems too small for the cut out? 

[revilla]

My theory for what it's worth:

It was primarily a piston failure. The piston crown has cracked across the inlet valve pockets, even though there's no obvious hard contact with the inlet valves. A known weak spot.

The broken off bit of piston was hitting the head, picking up the markings of the cutout seen.

The damaged piston broke up further and was rocking and locking in the bore rather than sliding properly, overloading the rod bolts leading to a fracture. They must have hung in loose for a bit allowing the bearings to get lunched.

With the big end cap gone the rod was thrown upwards smacking the piston onto the exhaust valves, bending them.

Next turn of the crank, the big end journal or crank web hit the hanging end of the rod and put it through the side of the block.

[p.mole1]

That sounds completely plausible, I now have a very long expensive shopping list 

[p.mole1]

Just checked my video footage from Cadwell Park and in the slow corners oil pressure dropped to a minimum of 30 psi at low revs then straight back up to 60 psi so everything looks fine. I just wish I set the camera at Anglesey it may have given me a bit of an insight to what happened before it let go.

[revilla]

I may be overthinking this but ...

If it was number 2 that failed then if I've turned it round in my head correctly that picture of the inside of the block shows very heavy hammering just below the bottom of the liner on the INLET side.

With the crank rotating clockwise viewed from the front, I would expect intuitively that if the big end came apart, the crank would hit the rod from left to right and punch the rod out through the right hand or EXHAUST side of the block, which is what eventually happened.

So that hammering occurred on the side where the piston was rising. The only way I can see damage like that occurring would be if the engine continued to make a number of revolutions with a very heavily distorted or broken con rod (otherwise it wouldn't hit the block) but with the big end largely intact (otherwise the piston would be pulled down on each stroke to make the next upstroke).

To my mind that further supports the idea that the initial damage started higher up the engine rather than originating in the big end bearing. I think the big end eventually fell victim to the extreme loads of a broken piston and rod.

Out of interest, do you have any good pictures showing the damage to No 2 liner?

[p.mole1]

Hi Andy a couple of days before the track day the engine was making what sounded like very light pinking at around 2500 to 4000 revs at around 5% throttle this disappeared at larger openings. I filled it with super unleaded and convinced myself it had gone away. My plan was to retard the timing slightly on those load sites but I didn't get time before Anglesey. The noise was audible on the way down to Anglesey but did not sound like anything to worry about. A lap before the engine let go the noise appeared to get worse but oil pressure remained the same. Just before it let go I was thinking that's a lot worse best back off and come in and investigate and it let go at full throttle at 6000 rpm. 

My theory is the bearing has somehow spun inside the rod, but it doesn't appear to be through lake of lubrication, since my oil pressure never dropped I assumed the noise was not really serious. Because of the complete destruction of the rod and piston it's difficult ascertain what happened. You can see where the rod looks like it's blued by heat. That's not say that the initial failure was a piston

You can't see it on the photo but there are holes on both sides of the block the biggest impact seems to have been on the inlet side.

 

 

 

[p.mole1]

I wonder if the noise I could hear earlier in the week was the cracked piston. I was warned by Dave Andrews to do regular compression checks as the pistons would be close to limit. Now I think about it the initial noise sounded nothing like a big end bearing. That would make sense under no load the cracked part of the piston could be making contact with the cylinder head making what sounded like pinking?

[revilla]

That's exactly what I was thinking.

[Tony Whitley]

Look on the bright side - you can make 3 nice paperweights like Ian Reynolds did!

[Englishmaninwales]

Sorry to hear about your pain.....Years ago my Mini 1275 GT engine provided me with lots of desk paperweights after it’s crank let go...

Malcolm

[Wrightpayne]

Me too with a 1380 mini - snapped rod bolt and rod exit left stage. It bent the cam 2 inches from the end and spun the flywheel shearing the tab washer. 8000rpm to zero in a split second dissipates a lot of energy. Head was OK.

[p.mole1]

Yes thanks I now have a lot of paper weight material ! 

[SLR No.77]

How is your Accusump plumbed in? Is there a possibility you're getting inaccurate readings when the pressure drops?

[p.mole1]

At first I I thought I may have plumbed in the Apollo backwards! but after removing and double checking every thing it was correct. The return pipe from the Apollo passes through a one way valve then via a tee piece feeding the Accusump, the return feed from the Apollo goes into the sandwich plate in the standard fashion. My feed for the oil pressure gauge is on the filter head and it measures the pressure of the oil returning into the block. The Accusump pressure switch is pre set to 35psi so as long as the oil pressure stays above 35 psi it does nothing.

[21jigsaw]

I think con rod / crank failure was the cause , due to the heat generated / blueing on the failed rod The remaining bearing show no sign of aeration and heat. The piston looks as though it made a one way trip to the valves and head and remained generally in tacked. If it had still been attached to the rod and the engine rotating it would have suffered a lot more damage. Is there any evidence that this bearing had slipped around resulting in oil starvation overheating and seizure. The heavy damage seems to be confined to the one bearing.

Dave

[p.mole1]

Hi Dave, it does seem strange that all the other bearings are fine, with no evidence of them picking up or deterioration  from lack of lubrication. The only thing I have found is the poor location of the big end bearings in the rods, I don't know if the bearing tangs are too narrow or the rods are poorly machined. I am sure I have read somewhere that Dave Andrews has had made single tang rods with a much better bearing location. 

[TRP]

Who mapped your engine if you had pinking? Unfortunately you have double tang rods (rover made single tang rods,I think they were fitted to early engines) and that won’t of helped. I used max speeding rods and omega pistons in my engine and couldn’t fault them, inconsistency in manufacture is the concern with Chinese rods but I’ve heard of a few people who’ve successfully used max speeding as well as me and the Chinese rods DVA sell run the same risks. That’s if you decide to rebuild it! Maybe a good time to stick a Duratec or busa engine in!

[p.mole1]

I've got a new bottom end with the oil rail, is it worth fitting the later uprated oil rail is there much difference?. Also I will be fitting forged pistons this will raise my compression ratio to around 11.2-1 although I'm not sure what my original compression ratio was. I think standard was around 10.5-1 although my head has had the chambers cleaned up so that would reduce it slightly. I'm hoping to get away without needing to remap the engine.

[p.mole1]

I'm using the DVA Max Speeding rods, I saw a set yesterday and I must say I was impressed with the finish of the rods. Streets better than the Rover ones. My Bill has reached £1800 but I think that's it. So not as bad as I first thought, it's amazing how bits like gaskets and seals add up.I managed to get the last windage tray from Redline!

[7 wonders of the world]

New pistons, raised compression ratio - you must get it remapped 

A dyno session should always be factored into the cost of an engine build

[ECR]

Have to agree re the re-mapping. If you don't, you risk damaging your newly built engine and that would be a tragedy...

It might be OK but then again ....

[Golf Juliet Tango]

I'm hoping to get away without needing to remap the engine.

Get it mapped. This is absolutely essential.

[TRP]

You need to measure your chamber volumes to really know how your compression ratio will be altered. What piston manufacturers say the compression ratio will be and what you actually get can sometimes be very different. I don’t think the uprated oil rail fits with Caterham dry sump systems, which may be worth considering if you ever plan to upgrade, which may not be a bad idea given your current situation! Have you had your injectors flow tested as another safety precaution? I’d definitely get the car mapped, potentially not with the same person as last time if it was pinking! Increasing the c.r. would only make that worse, it’s probably worth making sure you only use super unleaded too.