Piston Problems

[handi_andi]

Dear All

I have a bit of a problem. I have the head off as I think I had a blown head gasket due to oil in the coolant, although they is only a small amount of evidence on the engine block and head gasket that this was the case. That regardless I have just found the damage on piston 3 shown in the picture below. The other pistons appear to be ok and by the looks of it the block has been 0.2" over bored unless any one can shed any other light on all four pistons being marked QED 0.20 as shown in the pictures.

Obviously piston 3 needs replacing, despite the perfect compression between all four cylinders, as I do not want it disintegrating and ruining the engine. The engine has not been run for some time, as in about 8 months, so the clutch will be sezied on solid as per normal. As I see it there are two basic choices, pull the engine and replace the piston and probably all the big end bearings whilst I am there, which would also allow me to replace the clutch. Or, gvien I am running on a spyder chassis with a removable tie bar it looks like I could replace piston 3 with the engine in the car and then keep the clutch pedal down plus engine cycling to release the clutch. Hence I thought I would run a poll to see what everyone thinks before I do anything, as well as asking for any adive or comments people want to give.

Sincere thanks in advance.

Andy

[JJDraper]

Looks like the piston crown has broken off down to the piston ring. Can't see any evidence of scoring on the bore, so you may be able to source a new piston from QED, and fit it with the engine in place, although I have never done it myself..... Any takers?

Why did it break? Detonation; dodgy piston; bad karma? Can't say at this distance, but my advice is shrug shoulders and fix the problem.. May be linked to head gasket problem..

Jeremy

[types26/36]

Well I know what I would do but you don't have it in your poll,
I would drop the sump, remove all of the pistons, horn the bores, check the bores after horning (it will show if you have a ridge.....and how deep the ridge is) the finger nail test does not work! if the bores are reasonable then get a new set of +20 pistons (they don't have to be QED) then check the ring gap is in spec.
If one piston has broken on the ring grooves then the chances are the others will, I have seen it before and I put it down to fatigue with old pistons......that is of course only my opinion!
Drop a couple of main bearing caps just to see what the mains and crank look like and refit the new pistons with new b/e bearings.
The clutch is an other issue and you should be able to free that off if it is not too bad.
Even if you only fit one piston (assuming the other pistons look O.K.) you will need to horn that bore anyway, the correct way is to mic up the bores and pistons but I doubt you have the tools to do it but an motor engineering shop could do it if you wanted to get more involved.

[GrUmPyBoDgEr]

Have you thought about why that piston became damaged?
You my well get away with replacing the piston & shells etc, with the block still in the car but seeing as the cylinder head is already off there's very little work left to remove the engine.
With the engine out on a bench life is made so much easier.
Looking at the Photos, the colour is wrong for pre- ignition; to me it seems that excessive oil has caused a burn through to the top compression ring.
I think that the cylinder head & crankcase ventilation system need some serious looking at.

All the best
John

[handi_andi]

Hiya all

Interesting opions so far and have leant towards taking the engine out and would have it out this evening if only I had an engine crane, anyone got on in the North East of Scotland?

A couple of mysterys or explanations have come to light this afternoon. Firstly, a large portion of the fly wheel appears to be exposed on the exhaust side of the engine, as per the picture below. Is the cover plate wrong or could it be that the block is non-standard? As can be seen in the picture below the engine number is P26159 but appears to have been badly stamped in by hand as the numbers are all over the place. There is a number cast into the block on the exhaust side which appears to be 701M60155A, does this number make sense or could the block be off something else? The head is definently a big valve head as it has a 'N' on the raised post by the recess for plug 1 and the camshafts have two grooves on them.

There is coking on the cylinder head in the way of piston 3, and I have just brought a catch tank to improve the crankcase breathing and to reduce the amount of crap going through into the airbox in the way of the rear carb that had a fair amount of goo in the chokes when i was cleaning it up as part of refurbishing the carbs. In addition, when I brought the car the ignition timing was well off the mark and may well have been causing detonation problems and there was a knocking until I sorted the timing. Hence the theory about oil in the cylinder causing the piston problem could very well be true especially when the ignition problem is also taken into account. Many years ago I had the skirt of a cylinder fail on a landrover engine for no apparent reason but the surfaces looked like it was a well established fatigue crack. The surface in this case looks like it might have been there for some time. The bottom crack surface runs at about the same angle as the valve indent, the side surfaces are almost vertical but the gap is slightly bigger at the top than bottom. The edge of the bottom surface looks like it is rolled over towards the valve indent, which would imply it hasn't started from that edge but has ended there. This would therefore imply it has fractured from underneath and been ruptured upwards, however, I struggle to work out how this could of occurred. Any more theories anyone?

Cheers

Andy

[types26/36]

701M 6015 is the correct block for a BV engine

[types26/36]

Looks like you might have the wrong (or modified ) spacer plate between the eng/gearbox.
Just had another look at you pic......is there a plate between eng/gearbox? if not........engine out!

[handi_andi]

Thanks Brian! Looks like I am missing the upper part of the plate, so as you say the decision has to be engine out. Anyone out there got an upper plate going spare please?

Andy

[alexblack13]

Hi Andy,
I have an engine lift crane sitting in my garage. It belongs to a friend of a friend who I would check with to see if ok to lend it out
that being ok all you would need to do is collect it.

I also have put up my Mercer bore guage on Ebay for sale. Very usefull in these conditions. Just removes the guesswork. I am about to put it one elan.net too.

I agree with 26/36/74 Except I would take the engine out. Would you be doing this repair in situ lying on your back under the car?
Not on your nellie. Get it on the bench.

let me know if any good and I can ask the question. PM me..

Alex B....

[kstrutt11]

One point from hard learnt past experince many years ago, you must hone the bore before fitting the new piston otherwise it won't bed in properly and you will have massive blow by and oil consumption.(can be done in or out of car).

kevin

[andyelan]

Hi Andy

I intend to replace the pistons in my Plus 2 this week and I am aiming to do it with the engine in situe. I'll let you know how I get on.

Regards
Andy

[gerrym]

Hi, yes I have an engine crane you can borrow. Check out the PM for details.

Regards

Gerry