3.0 cylinders bored to 98mm any issues?
 

Rebuilding my 3.0 and the cylinders have the plating ruined by water sitting in it for a long time(car was a basket case). Thinking of boring cylinders to 98mm, replated by Milleneum and having custom pistons made. Has anyone done this, and if so have you had any issues with it? Thanks, Mike.

The maker of the enlargement will tell you that 98mm doesn't leave enough wall to support the head gasket. Preference would be Carrera cylinders because they seal metal to metal without a head gasket.
Bruce

Why bore them to 98mm? Simply have them stripped and replated to your desired spec. for your pistons. Whatever your 95mm piston diameter is, make sure the replated cyls have suitable clearance. In the case of JE pistons, if that's the piston brand you're considering, that bore spec would be 0.0015" larger than piston skirt dimension

Well my thinking was big pistons cost the same as little ones(going PMO's so the stock CIS pistons suck for that and they are toast), coating the cylinders costs the same regardless of bore size. I would love to find a Max Moritz or Wossner kit, but they seem pretty far and few between. I'm thinking the issue with the 3.0 cylinders being bored to 98mm is the head gasket ring gets real narrow on the piston side and could break. Thats why they recommend the 3.2 cylinder to do this. I think I can welds the head gasket ring up, resurface the top of the cylinder, bore to 98mm, have millinneum coat and finish hone them, and have pistons made to my spec for under 2K. Am I a dreamer?

There is a beveled edge on a Carrera cylinder for sealing surface.
Bruce

Bruce, can you explain where the bevel is or draw me a picture? What about running a shim style gasket on the welded up 3.0 cylinder?

You can see the surface on this cylinder is not flat it has a slight taper off to the edge. Keeps the combustion chamber nice and sealed.

http://tapatalk.imageshack.com/v2/14...ff6474a215.jpg

Craig, so the taper is proud or tallest at the bore? Thanks guys. Now the question is:
which rod bearings am I using in this 3.0 build:-)

Stripping and replating is a bit cheaper than boring larger and replating. Figure an additional $30 per cylinder

Cylinder Plating Prices | Cylinder Modifications | Piston Coatings | Diamond Honing | U.S. Chrome Corporation of Wisconsin Cylinder Repair Company

Plus you have to find a good used set of donor Carrera cylinders to bore out. Welding the tops of your current cyls is possible but I think would end up costing more in the end vs. finding a set of used Carrera cyls.

When you mention installing PMOs, that's a big difference. Installing carbs with the 98mm pistons will make your tuning of the engine a lot easier than if you stayed with CIS!

Here are some crappy pictures of how thin the wall gets when you bore a CE-ringed 95mm cyl to 98mm http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/724260-core-mahle-nikasil-cyls-98mm-sc-style.html