Piston over bore size needed

[steven4141]

Finally , got hold of a pair of Wiseco 20 thousandths over pistons (3.3325), since these are forged pistons can anyone tell me what I need to have my cylinders bored at? I'm thinking the clearance is less for forged pistons than it is for cast but I don't know what it should be. Anyone know what I should have the holes bored to? Thanks, I can't wait to finally start getting this baby back together. I've been waiting for the stars to align (money for parts & time to do it ) since last fall !! Man am I tired of fishing off the bank I guess I could have went cheap with some unknown Vertex pistons or something another, but if I'm gonna do it I like to do it right with the best parts I can get ya know. Thanks again, Y'all have been a great help on this little project since I started on it last fall.

 

[Faztbullet]

Re: Piston over bore size needed

If it where me I would have went with the Vertex but anyway.. Wiseco's are a forged piston and OEM's are cast. Anytime I install a Wiseco in a customers engine I bore it(have my own boring bar) 1/2 thousands larger due to the expansion rate of piston.(forged expands faster than cast) Most scuffing and damage caused by Wiseco pistons are customer related as they do not let engine reach temp before use(read pamplet with piston)So your finished bore size using Wiseco's would be 3.333 as OEM bore is 3.312. and make sure you replace t-stats/water pump. Wiseco's work great in standard bores that have some wear on them...

 

[moparman]

Re: Piston over bore size needed

the wiseco pistons will come with an info sheet with their recommendation for clearance of the piston to wall clearance[forged pistons usually require more clearance because of the silicone content,it expands more than the cast pistons with less silicone in them]. I usually follow their recommendations EXCEPT when using their product out of their intended applications[i.e. using them for a non-listed application or different engine than listed for]. Good luck with your engine rebuild and many happy hours of boating. MOPARMAN ROLL TIDE 13-0 championship bound

 

[Frank Acampora]

Re: Piston over bore size needed

Don't go crazy! I have used a good number of WISECO pistons (around 50) using the standard overbore with no ill results. No binding, galling, scratching--in short, no problems at all. So: Just have the machine shop overbore .020. In this case 3.3325.

The ONLY time you need to worry about clearance is if the engine has been modified for performance and racing.

BTW: all Force pistons are cam ground and not perfectly circular to account for the differential heating and expansion. So if the shop decides to "mike" them, they will find a major and minor diameter.