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Removing the ridge from tops of cylinder bores.
https://www.ausmini.com/forums/viewtopic.php?f=2&t=18275		 Page 1 of 1
Author:  supercharged 850 [ Tue Apr 18, 2006 12:14 am ]
Post subject:  Removing the ridge from tops of cylinder bores.
Has anybody done their own bore ridge removal?

I need to get my 998 block done and am wondering if it is a good idea to give it a shot myself, with a ridge removal tool of course (and NO i dont want to overbore the sizes)

OR.... if it is only slight, could I get away with leaving the ridges there???????
Author:  1071 [ Tue Apr 18, 2006 3:57 am ]
Post subject: 
"getting the block done"??

The ridge is what is left of the unworn cylinder wall. Yes you need an overbore - unless you're diabolically lucky enough so that the bore has worn evenly and concerntrically....chances of this happening?? virtually nil.

If you have a ridge, your bores are badly worn and need to be cleaned up.

Cheers, Ian
Author:  HPDesign [ Tue Apr 18, 2006 12:06 pm ]
Post subject: 
that ridge was actually the original size of the bore of the 998, if you remove the ridge with out overboring the cylinder it won't thel you at all. in fact it will decrease your compression ratio. my advice is you will need to either overbore it just .20 thou. or if the motor's still strong then just leasve it as is. my advice of it's a decent step, bore & hone. new pistons and rings. while your head's off take it down the head shop and get unleaded seats in it.
Author:  supercharged 850 [ Tue Apr 18, 2006 8:59 pm ]
Post subject: 
Already got the unleaded head 8)

The problem is, I just bought a second hand A+ crank, rods and pistons to go into this early 998 block. If i need to rebore the block, the pistons will be useless. I want to keep these pistons because 1) they are flat top, 2) they are fairly light due to short skirts, and 3) i've already bought them :lol:

The plan WAS to use the A+ crank rods and pistons, but fit new rings. I was hoping to get away with just honing the block.

Its just a race motor... maybe i'll leave the ridge there. The ridge isnt huge.... you can just feel it.

I might need to get it measured. Time to buy an inside-micrometer :roll:
Author:  simon k [ Tue Apr 18, 2006 9:15 pm ]
Post subject: 
shoulda looked at the bores before you bought the pistons..... ;)

if the top ring on the new pistons are higher than the old pistons, then the first time they travel up the bores then they'll be destroyed..... and that's likely to be the case given they're speccy flat tops

If it was a street motor, and wasn't going to be driven under race conditions you might get away with it, but the extra crank flex you get when really fanging will also push the top rings past that wear mark and break them

if you're lucky and the ridge is only slight (like you say) and you can get away with a hone and have slightly more clearance around the pistons then you'll be OK, but it'll cost you a few compression points

what about finding another block... ?
Author:  supercharged 850 [ Tue Apr 18, 2006 10:09 pm ]
Post subject: 
skssgn wrote:
shoulda looked at the bores before you bought the pistons..... ;)

if the top ring on the new pistons are higher than the old pistons.....

what about finding another block... ?


I did look, and feel, and thought it was passable..... Its not the first block Ive bought either. The first one had major damage from a piston and pin that came apart.....

The flat top pistons have a low top ring....... might be okay.... who knows.

Image
Author:  Morris 1100 [ Wed Apr 19, 2006 7:29 pm ]
Post subject: 
I have a ridge removing tool but I am a bit far away!
Lots of older engine shops would have them. Ask around.
If you don't remove the ridge you will probably stuff the rings and probably score the bores with the broken rings.
Author:  smac [ Thu Apr 20, 2006 6:56 am ]
Post subject: 
You guys are making a huge assumption that the ridge is due to bore wear. It could just as likely be a build up of carbon/crap in an inefficiently burning engine, the same as the build up that ends up on piston tops and in the chamber. If this is the case then it can be removed.
Author:  supercharged 850 [ Fri Apr 21, 2006 2:08 am ]
Post subject: 
In this case it is most definitely a steel ridge and not a carbon one.

Had a real close look at it yesterday..... the ridges are only on the top of one side (50%) of the bores...... and you would easily be fooled into thinking that somebody has actually threaded the bore in that location. Strange indeed. :?
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