Damage to 16v 82.5mm Wossner forged pistons (new photos)

Well wot a bad day i've had [:^(]

Took the MK1 for a Birthday spin increased fuelling as it was running abit lean.

When i got home took plugs out but No.1 cylinder plug had stripped thread sh*t don't know how that happened.

so took head off again, i will be able to rethread the 10mm x 1.25mm thread.

then noticed damage on the cylinderr head on all cylinders.



Mrks on the Head centre on each one on the lefT and righthand side

The look at the pistons each one of the brand new wossner pistons had a 1" line on both side were it had been catching the head



So the Wossner pistons i had to wait 8 weeks for to be specially arn't that special, will have to speak to TSR Monday.


Damaged spark plug


can anybody shed any light on this , now i know why the compressed was so high with the pistons such a tight fit.

Shall i fit two head gaskets?

Update ! Piston crown protrudes 4mm above the block level, will need two gaskets i think.

 

Pictures are not good enough to see any detail

 

ouch,could try a diesel head gasket,they come in different thickness`s?

 

Oh no, not good :-( You have me worried now for my VR I am about to assemble. Did I read somewhere about putting a very thin layer of plastecine / blu-tac on the top of the piston and turn the engine over by hand to check clearance?

 

I Had a diesel gasket fitted , the marks ar 25mm long and about 0.5mm deep, it looks like the piston crown is too big

who has a dremel dye grinder i can borrow ?

The valves are fine they havn't touched them plenty of clearance.

 

Can't see the pics I'm afraid. Try taking them from a few inches further away.

I'd advise the plasticine trick. It's possible that they've sent you pistons with too high a deck height. Good that you've spotted it before it did any major damage. How far proud of the block face are they sitting?

 

Shoot mate, that's a blow! Seems weird that the valves didn't kiss but the pistons did [:^(]

I have a head spacer that reduces comp by 1 point (about 2mm thick), although two stacked metal gaskets would acheive about the same. Get the modelling clay out to see how close the valves get, they may be very close too. Should have about 2mm ish clearance (theres a calc obvs).

Is you head ABF too?

All part of the fun mate -

 

hello mate sorry to hear about the pistons,as i told you a while ago i have the same set of pistons and after you said you thought the valve clearances were a bit tight i built the motor up using plastercene and as far as i can tell i have at least 1.5mm clearence on valves and piston to head?my bore is i think 0.50mm bigger than yours but would that make that much differance?i am running 288 deg cams
shouid i be scared?

 

was there any gasket overlap?

 

Take some better pictures as we cannot see anything. A bit of a shame considering you just built the motor.

 

Blimey brooksters, cant beleive that!

As above get some clearer pictures mate, loads of peps here who can offer good advice

 

Will get some good pix in to morning.

The Headgasket was fine untouched and so were the Valves.

Is the ABF Head combustion chamber area slightly wider than a KR thats the only thing i can think of and that maybe why the KR has higher compression with the ABF bottom end.

If i fit two head gaskets this will bring the compression back down to 12:1
Pix below show before head was fitted and how high the piston crown is.



And the KR Head before the damage.

 

Good morning everyone

just measured the piston crown and it raises 4mm ! above block level thats why the compression was so high.

i think it will certainly reuired two head gaskets

 

I don't want to sound too negative here, but the fact is you've got a bit of a hybrid mishmash of parts there, so be careful what you tell wossner if you go along the route of blaming them,

 

got any photo's of an ABF Head to compare shape.

 

ouch

 

has the head been skimmed aswel. as that can't help.

looks like it may have been.

hope you get it sorted, and that nothing is irrepairable

 

Just found the information .

Wossner ABF 9032D Piston comp height 31.6mm


Wossner 9A 9031D Piston comp height 30.6mm


The ABF Piston is 1.4mm taller than the 9A so this explains the higher compression. About 0.4mm too much for the KR Head.

The marks on the piston are just like deep scratches to will be ok but i will go down the twin gasket route.

 

Head has never been skimmed.

One thing for sure the compression must have been way above 13:1

 

It looks like the head might have had about 1mm off, by the shots of the valves. You can't take much more than that off a 16v head.

I think your best solution might be to have the pistons or the head chamber edges machined down a little bit. You should check the clearances to the valves though, as you need to allow a bit extra for valve and piston float at high revs, or what's fine on tickover might go horribly wrong on the track. Obviously, you need to check the thickness of the piston crown first.

2 gaskets should work but it's a bit of a bodge, and will lose you more compression than just machining the right areas.

What cams are you running? That'll dictate the CR your engine can cope with.