High Piston Protrusion

[wil892]

Hi guys,

Just putting together my second 1.6td engine after my first one ran for 60k burning oil (built when I was 19 could have been more carefull!)

Background:
Spare block acid stripped and bored 0.5mm over
Used OS Kolbenschmidt pistons originally used in first build

My original rebuild had low 1 notch pistons due to me not machining the deck surface coupled with the OS pistons having allowance for this.

With the new block I had the deck machined 0.006" to bring the pistons up to around a high 1 notch or 2 notch.

After the block work the machine shop I used had a look at the small end bushings in the con rods and checked for play which resulted in them being replaced. (The small end bushings had never been replaced so had at least a good 200k miles of hard driving)

Fast forward, i've now fitted pistons and checked protrusion
Cyl. 1 - 0.97mm
Cyl. 2 - 1.04mm
Cyl. 3 - 0.97mm
Cyl. 4 - 0.98mm

I've got a feeling the new small end bushes have resulted in the pistons being higher up the bore and coupled with the deck machining I now have a piston which falls out of the 1.02mm max height tolerance of a 3 notch gasket by 0.02mm!

Can anyone lend some advice? I don't think i'm happy risking it and would like the piston down to where the rest of them are any thoughts on how this can be achieved?

Before anyone questions this machine shop I learnt my lesson from last time and used a place which is highly regarded in this part of the country and they have been much more reassuring then the last place I used!.

Thanks

Will

[fatmobile]

Maybe try swapping the high piston with a low one.

[rabbid79]

Maybe try swapping the high piston with a low one.

That's a great idea.  Also possibly try swapping piston and rod combinations.

[wil892]

Thanks great ideas I'll have a go at that.

One other thing, I have only torqued the conrod nuts to 30NM so far before their final 1/4 turn. Could this affect the piston height?

The conrod bolts were new last time I rebuilt the engine and have been fully torqued only once so they supposedly have one more torque.

[fatmobile]

No I don't think that 1/4 turn would change anything enough to matter.

[rabbid79]

The conrod bolts were new last time I rebuilt the engine and have been fully torqued only once so they supposedly have one more torque.

This seems a bit odd.  I'm not a bolt expert, but from the sound of it, you're suggesting that your connecting rod bolts can be used 2 times, but no more?  I've heard of Torque To Yield bolts which can be used one time, and conventional bolts which can be used many times, but I've not heard of bolts that can only be used twice.  Your reference to a "final 1/4 turn" suggests they're TTY bolts.  What am I missing?

[wil892]

The conrod bolts used in this engine are also used in the G60 engine so quite heavy duty, and i've tried to find out if they are TTY or not and as far as I can tell the bentley manual allows one reuse of these particular bolts.

Anyway, last time i installed these conrods I replaced the bolts on them so they have only had one torque applied.

[rabbid79]

Thanks for the reply.  That's really interesting.