1.5mm too much to cut on piston ring gapping?

[vas]

Hi,

got a set of Wossner pistons for my 2.0lt 16v turbo engine (Fiat Coupe)
Bore is 84.60mm (well, piston 84.50mm)
Rings that came with them are 85mm, checked and measured them in the bore and seems like I need to remove almost 1.5mm off the ring to gap them to the specified 0.3mm. The guy putting the engine together claims that this is too much and the rings are never going to seal properly on the bore hence we should try and find the "proper" rings for the bore.
Checking Wossner's site, it seems that these are the ones they specify for the particular bore.

So, Q, is is OK to cut 1.5mm more or less off the ring or the curvature is going to be wrong and cause problems?

thank you

Vassilis

[Guy Croft]

They will be OK, I have done that.

GC

[vas]

thanks for the quick reply Guy,

would it be okay to cut them using my dremel and leave the final bit of cleaning/clearing for stone? Or will the temps weaken the material (I doubt it since it wont be up to the 1000 or so Centigrade that they'll be working in the engine...

V.

[Guy Croft]

For starters see:

http://guy-croft.com/viewtopic.php?t=761

For that amount you need to mark one ring end with a black indelible felt pen and scribe across radially with a sharp point so that you have a line to grind to. I'd do the initial removal (leaving a few thou in hand) on the side of the grinding wheel, remember you should grind from the outside inwards.

Dress the sharp edges with a fine carborundun stone before offering to bore and adjust the last little bit with a very sharp (ie: new) file and stone the edges again for the final job.

Top rings are often steel or ductile iron and pretty 'bendy' ie: not prone to snapping. The second ring is almost always cast-iron and very easily fractured. Handle rings with extreme care during gapping and fitting, and make sure no grinding debris goes on the crank during trial fit - note my protective paper in the bores in my photo.

GC