Uh Oh Part 2!

[Jrod 7]

Piston rings were new about 1500 miles ago, liners were honed by QEP.

 

Not saying its not them just means they failed very quickly if it is!

[Cameron 16]

Piston rings are really quite brittle, so could be possible that one was damaged when fitting and has now broken. Definitely worth taking the piston out and having a look.

[DamirGTI 323]

You might broken it during the assembly inside the liner it happened to me once though on a outboard two stroke looper engine with awkward cylinder access for my piston ring compressor tool .. and the piston had very similar clonking sound sideways as the one on your vid ...

 

Damir

[Jrod 7]

Piston rings are really quite brittle, so could be possible that one was damaged when fitting and has now broken. Definitely worth taking the piston out and having a look.

 

I will be taking it out at some point thats for sure. Should a piston move like that though even if the piston rings are broken, are the little ends likely to be shagged aswell?

 

 

You might broken it during the assembly inside the liner it happened to me once though on a outboard two stroke looper engine with awkward cylinder access for my piston ring compressor tool .. and the piston had very similar clonking sound sideways as the one on your vid ...

 

Damir

 

I didn't as I didn't build it! If it was broken on assembly would it of done 1500 miles...?

[DamirGTI 323]

.. just a sec. .. i'll need to dig a photo of .. well you'll see

 

Damir

Edited October 18, 2009 by DamirGTI

[Cameron 16]

Well it may not have been broken, just damaged. If it was slightly cracked then the repeated heating / cooling and general abuse could have easily finished it off. I don't see why the little end would have suffered too much from it.

[DamirGTI 323]

I didn't as I didn't build it! If it was broken on assembly would it of done 1500 miles...?

 

This one did , well , a few years inside the engine i guess and pulled without any probs 200kmh flat out on the motorway :

 

 

.. and it would probably be still running if my mate didn't opened up the engine (but not because of the strange sound , uneven running or anything like that - he bought this complete car a 309 16v for a project and therefore opened the engine in order to rebuild it ... and found this inside )

 

 

Damir

Edited October 18, 2009 by DamirGTI

[Galifrey 1]

A small end broken on its own wouldnt account for that much free play in the bore, especially as the conrod would allow that movement even if the small end was perfect.

 

I suspect the bore and piston are way out of tolerance for some reason ovalling seems possible as mentioned above, with no signs of seizure then even a broken ring wouldn't on its own allow that much extra movement, the piston on its own with no rings shouldn't move that much?

 

Piston slap would account for the noise, so it is possible the piston skirt has failed/cracked, although it looks so far out of tolerance, piston slap seems almost a certainty.

[Cameron 16]

Yeah that amount of piston slap would make a hell of a racket! Could be that a failed ring has damaged the piston skirt, or vice versa.

[DrSarty 90 1 Cars]

So the big question is...have you confronted QEP about this?

[Jrod 7]

So the big question is...have you confronted QEP about this?

 

 

No, Should I be then?

 

So whats actually wrong? The piston is not the right size for the liner?

Edited October 19, 2009 by Jrod

[Dave_McC 0]

.....before QEP get a slating on here......

 

It was me that Jordan bought the car off. When I sold it I honestly wasn't aware there were any problems with it - so I have been lurking here feeling slightly guilty - but as I've learnt in the past it is a risk in buying any car privately.

 

I built the Mi engine in the car - not QEP. QEP did do all the machining work for me, but at no point did they have the whole engine or do checks for compatability / tolerance of parts, with a couple of exceptions.

 

Re the pistons - I bought them 2nd hand off someone on here (they were in a built up bottom end) - they already had rings fitted (except 1 which they'd broken trying to fit it - I got QEP to fit a replacement for this one ring).

 

As to why the piston crowns were machined - QEP had to deck the top of the block in order to get the liner protrusion right after re-machining the liner seats in the block - as a result the compression ratio would have been too high, so the piston crowns were machined slightly to return the CR to standard.

 

Having built the engine I ran the car for just over 1000 miles before putting it up for sale - as I wanted to be sure it was running ok - and bar a couple of electrical issues I had (and sorted) it didn't miss a beat in those 1000 miles - didn't use any water or oil nor did it make any strange noises.

 

The blame can't be laid at QEP's door - there are too many other variables. Whilst they did hone the liners, the engine has since done maybe 1500 miles, possibly with another fault for some / all of those miles which could have damaged the liner(s). Many of the parts were secondhand and hence the risk that carries - including the guy I bought the bottom end of the engine from who could have been hamfisted fitting the pistons and hence the rings may have been already weakened when I got them - who knows.

 

I have built another engine previously - a K series running 210bp which has happily done 6000 plus miles in a Caterham including several track days - but I could have f***ed something up.

 

Dave

[Cameron 16]

I don't think anybody is blaming anyone here, and as you said since there are so many unknowns with this engine it would be unwise for people to start pointing fingers.

 

Just out of interest, do you know which cylinder had the broken ring before you fixed it? Because if it were a different cylinder to the current dead one it could suggest that the first builder damaged more than one ring.

[Galifrey 1]

I think it is more important that we establish what PART of the engine is to blame before we speculate WHO.

 

Good of Dave to post about how the engine came about, at least this eliminates QEP from any accountability on the liners/piston fit.

 

Unless the bores are properly mic'd and checked against the pistons, this kind of thing can happen, so there may be an issue there, but at the very least, the engine now needs to come apart for a proper check. Hopefully, the worst that will be required is a new piston and a liner to put the engine back to its former glory.

 

Cameron, if the ring broke during ring fitting, this should not have caused any issue, however, if it was during piston fitting there could have been some piston/bore damage, but i think this would be evident on the bore in some degree, which from the current pics it isnt.

 

If all the rings are broken, the piston may mode slightly more easily, but it seems to move a lot, which indicates to me, the piston and liner are the biggest issue rather than the rings (I will happily admit my error if I turn out wrong here).

 

The liner needs to come out and be checked for ovalling IMHO

[Cameron 16]

Definitely.

 

Jrod - have you had the engine apart yet?

[Jrod 7]

Dave, I just want to let you know I don't blame you and I havn't said anything about QEP as I've no idea whats even wrong with it really! I just seem to have alot of bad luck! :)

 

As to taking it apart, No not yet. I only work on it weekends so will try Sunday. I've never removed a piston before so am a little apprehensive to be fair!

[EdCherry 34 1 Cars]

Its easy peasy, insides of engines are just a couple of bolts, twiddle your fingers and all of a sudden mess everywhere and engine parts too!

[Cameron 16]

Yeah removing stuff is easy peasy. If you haven't already, take the sump off then just undo the big-end cap bolts and push the piston out the bore. You need to be careful not to break the liner seal but that's about it. Oh, and make sure you note which way round the bearing cap fits on the con-rod! Whack a little paint mark on the inlet side or something like that.

[Jrod 7]

Will do. I might even try tomorrow.

[EdCherry 34 1 Cars]

Go out an try it now, harden up man real people work on there cars as soon as they break!

 

P.S. I am exempt of this 'rule'

Edited October 20, 2009 by EdCherry

[welshpug 1,621]

I wouldnt be particularly worried about the liner seals, they're cheap enough to replace.

[Cameron 16]

They are, but it's a ballache having to clean the rust and crap from the base in order to get a decent seal, and unless you're taking the crank out you'll have to be very careful about where all the flakes of crap go! Much easier to just take the time and care to not disturb the liners IMO.

[Jrod 7]

They are, but it's a ballache having to clean the rust and crap from the base in order to get a decent seal, and unless you're taking the crank out you'll have to be very careful about where all the flakes of crap go! Much easier to just take the time and care to not disturb the liners IMO.

 

Shouldn't be any rust in there already? Still, I'll be careful.

[EdCherry 34 1 Cars]

There will be rust, you've put water inside it!

[Jrod 7]

Well, not much! theres not been water in it long!