Hello!

I have a set of speedpro pistons (flat top), on each piston there is an arrow pointing, do the arrow has to point to the front of the engine or to the back ?

Thanks !

thats just their logo I believe...it doesnt matter which way.

Hmm on stock pistons there is a dimple that goes to the front of the block. Are the pistons 2 or 4 valve relief? If they are 2VR and 4 have the arrow on one side, and 4 have the arrow on the other side of the piston then the arrow goes to the front of the block. That would only make since if you already have your connecting rods installed and those only go in one way for sure.

The "Arrow" points to the Front of the engine.
Your machinist would (should/) have indexed the Rods to the Pistons so that they will be in the right orientation when you install them. Four will be pressed one direction and four will be pressed the other.
The 'arrow' indicates which is the thrust side of the piston.

As Vintage and others have stated, the arrow goes to the front. This is probably due to the wrist pin offest and/or valve reliefs. They are usualy offset to one side rather than built dead center in order to reduce noise while cold. This is used on stock pistons and many rebuilder pistons. Some high performance pistons are manufactured with the wrist pin dead center but they are less common.

-Mark.

lol. my bad.

You can reverse them on the rods with four notches to gain a schosh better "angularity" if they are offset pin type.

Should be offset something like .060" or so which means every little bit helps. Imho...

But they will slap a schosh more when cold so it's a trade-off..

My Machinist did it to my junk 301 to make her a little happier up top. pdq67

arrow = front of engine.