AAN piston to bore clearance.

[popdemonic]

Just finsished checking the AAN block.i used the dial bore gauge
Checking diagonally from top and bottom of the cylinders.
All 5 cylinders are all within permisssible tolerance 81.03-81.04mm
(Stock bore 81.00-81.01).maximum out of round is 0.01mm and
Taper is 0.005mm.anyway the block will need to send out for a honing
Service.i searched on the google and found normally the honing
will take out 0.0003"(0.075mm) of material.In other words,
After honing job the cylinder bores will be 81.11mm.i
Dont know if bore will be too excessive enalarged and caused
The pistons slapped? The 1st oversized bore is 81.26mm.
i'm not going to go for oversized pistons besides,if necessary.
TIA.

[diesel des]

I always like a new clean bore when doing a engine build. Fcp do nice wossner style own brand pistons at a good price. Wossner and their version of them run tight clearances and give no slap.

Sent from my LG-H955 using Tapatalk

[UrS4boy]

I always like a new clean bore when doing a engine build. Fcp do nice wossner style own brand pistons at a good price. Wossner and their version of them run tight clearances and give no slap.

Do you use a torque plate (head substitute) when doing this?

[diesel des]

No I personally don't. The bore is more likely to distort when heated as well as being under the tension of the head studs. Cylinder pressure also distorts the bore so I don't feel that just a torque plate is worth while.

Sent from my LG-H955 using Tapatalk

[Cordoba16vt]

My 345 000km then block was honed during overhaul - just changed rings ( new Mahle style ) , bearings, seals , etc + 7A head . Engine compression is good , when descending in 1st or 2nd gear you can feel good engine braking power. No smoke whatsoever , some excessive oil consumtion - 2 lt per 10 000 km , on RS2 turbo with a label clearly indicating it was made in 1994

Prior to rebuild inspection there was clear signs of original honing present with some minor glazing halfway down the bore. Honing is 0.01mm anyway and if done properly is good for setting in the new piston rings .

Anything up to 0.1mm between piston and cylinder will not make pistons slap or excessive oil consuption, due to bore/stroke ratio, piston design ( long skirts , etc...) , if built properly .

All the best

Ivan

[orignalS60]

@pop you can buy oversized rings from
goetze. Then gap them appropriately for
the added bore.

[popdemonic]

@pop you can buy oversized rings from
goetze. Then gap them appropriately for
the added bore.

Yeah,Normally when we went for oversized rings it means we also need oversized pistons IIRC?

[orignalS60]

They are for stock pistons. They are 0.020"
oversize. Bigger pistons run .5mm at a time.
The oversize rings are for worn bores after
refurbing them with a nice hone.

If you want you could always buy some 81.5mm-82mm
forged pistons so you'll have fresh bores with your
pistons fitted to them.

[orignalS60]

http://www.rockauto.com/m/mobilecatalog.php

[orignalS60]

^^^Go under piston rings.

[popdemonic]

Thanks mate.