I m building a 301 Chrysler poly engine and the replacement pistons have a slot from the oil rings down to the skirt on one side only.. The piston has no "ft" markings on it. So what side does the slot face toward? the cam or the outer side of the engine? There are no directions with the pistons.
Sometimes on the outside of the one of the pin bosses there is an "F" cast into it designating the direction. But on other pistons of this style i've seen, the slit goes toward the cam(on a V-style engine).
Usually, CAST pistons will have a notch or other marking on the top of the piston that goes towards the FRONT of the block. FORGED pistons have NO such marking. Another thing is, the pin is usually offset to one side, however, I don't recall what side the offset is on. Some guys will flip the offset pin side; it supposedly lets the engine rev faster/higher. Maybe someone will jump in on that. Butch/56sedandelivery. Just looked in my 59 edition MOTORS MANUAL, and they have the notch in the top of the piston facing forward, and the stock pistons have "FRONT" also cast in the front of the piston. Looks like they are a full floating pin also. Now, IF the pistons are already hung on the rods, on the rod/crank journal, the large chamfer faces the rear on the right bank #'s 2,4,6,8; the large chamfer goes to the front on the left bank, #'s 1,3,5,7. The book does't say anything else about the pistons as far as what direction they face. Butch/56sedandelivery.
^^^ Good info. Also as far as the slot you refer to: Some early Chrysler engines had a slot that runs down one side of the piston to allow tighter clearances on cold pistons and the slot allowed room for expansion when at operating temp. Did the original pistons have a slot in one side?
There is no common method that the aftermarket uses for identifying the piston front. Each piston company uses their own way to do this. It doesn't matter if they are cast or forged, they can have an arrow etched into the top indicating this, or a dot or notch....or nothing. Some Fords have an "F" cast into the side of the pin bosses, some are on the underside of the piston. On some brands, only valve reliefs are the only clue as to the direction they need to be installed. The main problem with trying to use engine manuals to figure this out is that they are written to address the use of OEM parts and not aftermarket ones and are often no help when used in this way.
They are cast aluminum pistons.. Theirs no offset.. No champher.. No F...the old pistons had no slots... I don't want to have to take it apart if I put it together wrong.it does have a tiny intake valve relief on opposite sides of each other
Try this: Ask the supplier or manufacturer. All we can do is guess because we don't know what you have in front of you and/or know what the manufacturer has designed... As mentioned, 'most' pistons have some kind of marking, take a second hard look. Without confirmation from the manufacturer, I'd agree with 26T's thoughts. .
I got them from someone who just puts kits together and sells them..that intern came from a machine shop who is also scratching his head on this question..lol Posted using the Full Custom H.A.M.B. App!
Slot goes in the direction of rotation or away from the thrust side. On the power stroke the rod pushes the piston away from the direction of rotation or towards the passenger side.
A couple pictures. If you have non symmetrical valve notches, I would think there would be four pistons for the left bank and 4 for the right bank.
It sounds like you've got your answer already, but are you certain that there's no pin offset? It could be so slight that you likely couldn't detect it visually. But I couldn't tell you how or where to measure it to say for sure.
An easy way to measure is with a caliper, but depending on the piston diameter some jaws might not reach...inside of pin bore to od of piston. Check each side. The difference is the offset. .
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