stock bore size?

[DAVE69]

I was wondering what the stock bore size on a 3.8 is?I have my engine apart and started doing some measuring and this is what I found Bores are @ 3.8(+,- .0005) And my pistons are @ 3.796(+,-)@ the skirt.The pistons do not look like they are worn ,this gives me too much clearance .004 , (.0008-.0020) is recomended.I thought the stock bore was 3.8 if so the pistons must have worn.So I guess my question is what is the size of a standard size forged piston, and do they make a say a .005 over piston.The engine ran fine, no smoke,I just got stupid with the boost on the most beautiful,straight, flat deserted piece of road I have found in a long time and of course lost two head gaskets so I figured I might as well tear the motor down.any help would be apprieciated thanks Dave

 

[84BuickGNYorkPA]

Dave,

I think you are fine with what you have 3.800 is the stock bore size. I would do a light hone, fresh rings, bearings, timing chain and a good valve job with fresh springs and you will be ready to go...

Chuck

 

[gossamer]

The bore size on these engines is 3.800" when at standard size and 3.400" stroke. I assume you are measuring the skirt 90deg. from the wrist pin. Some forged pistons do run a lot of piston to wall clearance so it sounds like you are probably within spec. What brand of pistons are they?
I don't know of any brand of piston that is offered in a .005 oversize. You would have to run a file to type ring if you did find them.

 

[DAVE69]

The pistons are stock and I did measure them 90 deg to the pin .I was just a little suprised when I stuck the bore gauge in and found that the bores were pretty straight and to size,and that the pistons were loose.The pistons look pretty good,no marks, engine has about 75k .I'm just not sure if I want to bore,new pistons, caps, etc.............. it sort of snowballs.I just wanted to freshen it up,(original eng) and if I wanted to build a go fast eng start with another block.

 

[Nick Micale]

...., and do they make a say a .005 over piston.......... Dave

We have ordered and used 0.010" over pistons. This allows a clean up bore to true the cylinder walls, and then hone to proper clearance.

This is the way we did a recent GNX engine build and were able to use a standard ring package.