New pistons

[Philip]

Going to bore my engine for new pistons.It measures .006 over standard will .020
Overs clean up or should I go ahead and get .030 pistons thanks philip

[Kerry]

Buying pistons can be a little premature, I've had blocks that have taken as much as from a STD to .060 before they have cleaned up.
Your machine shop will work it out for what to order.

[Jerry VanOoteghem]

Going to bore my engine for new pistons.It measures .006 over standard will .020
Overs clean up or should I go ahead and get .030 pistons thanks philip

It all depends on how bad the bores are now. You say you're .006 over right now, but how much taper and out-of-round are you? Did you measure all up and down the bores, (e.g. top, middle & bottom), and at take measurements parallel & perpendicular to the crankshaft centerline? Until you really "map out" the full contour and wear pattern of your bores you really don't know how big you need to go. When that's determined, you can order the pistons accordingly and hand them over to the machine shop, who will want them in advance, in order the fit them properly. Chances are, it may be best to just have the shop tell you what size to buy. That doesn't put them in a bind if you buy something that they have to struggle with to make work.
That assumes you're planning to have the machine work done by others I suppose... Either way though, the first bit of advice is what I suggest.

[Dan Hatch]

First thing I do with a block is get it vatted and check for cracks. You will be surprised what you will find. You do not want to spend money on a bad block. Dan

[ModelTWoods]

Going to bore my engine for new pistons.It measures .006 over standard will .020
Overs clean up or should I go ahead and get .030 pistons thanks philip

It all depends on how bad the bores are now. You say you're .006 over right now, but how much taper and out-of-round are you? Did you measure all up and down the bores, (e.g. top, middle & bottom), and at take measurements parallel & perpendicular to the crankshaft centerline? Until you really "map out" the full contour and wear pattern of your bores you really don't know how big you need to go. When that's determined, you can order the pistons accordingly and hand them over to the machine shop, who will want them in advance, in order the fit them properly. Chances are, it may be best to just have the shop tell you what size to buy. That doesn't put them in a bind if you buy something that they have to struggle with to make work.
That assumes you're planning to have the machine work done by others I suppose... Either way though, the first bit of advice is what I suggest.

Like Jerry said, there are all kinds of measurements to take and consider before deciding on how much to bore a block. With a block that you have measured to be only .006 over, maybe you'll be lucky and not run into adverse taper or wear in other directions. If the block has been a running engine and protected from the weather, you probably don't have to worry about rust scale or pitting in the bores, but if it hasn't been protected, you might have to bore enough to clean it up. To shorten this answer, must T owners will recommend boring the least amount possible, unless you have a garage full of block cores.

[Allan]

Dan and Frank offer best advice. Get the block hot tanked and crack tested first. Then let the machine shop test bore it to see where it cleans up. Then order your pistons.

Hope this helps.
Allan from down under.

[Jem]

And when you get to fitting them, don't trust the 'as supplied' wrist pin clearance. I've had 2 engines seize up with tight wrist pins after a couple of thousand miles.