piston Q

POLAR_JEEP_04

NAXJA Forum User
Location
Ohio
so I have a 95 I6 block I have been working on tearing down to start my stroker project and when I got the head off I found writing on the pistons looks like it says

fr
>
50

I'm assuming that it means front with the arrow, but does the 50 mean that the motor is bored 50 over? If no one knows what im talking about ill get a pic up later.
 
I'll take a look at my old 94 piston tops tomorrow and the pistons in a 96 block I have in the shed and see what they have on em.
 
The pistons in the 01 I was foolin with today didn't have anything but the V on them--I forgot to check the 94s and 96s. I pressure washed the 00 stamped 0331 head and didn't see any cracks in the spring area but did see interesting casting seams/hairline cracks on the surface coming off the triangles of the coolant ports(will post pics tomorrow).
 
50 isn't the over bore. I have seen that before on stock pistons an dother people have made comments in other threads on it.

any clue what it is? ill post pics later tonight
 
"50" refers to the gudgeon pin offset - it's not on centre, it's .050" off-centre. This is done to help with piston slap (and, in fact, reversing pistons is an old trick to get a touch more power - you're increasing leverage on the crankpin through the connecting rod.)

It's still a slighly odd number - it's typically .060" instead.

Typical overbore piston sizes are: +.010", +.030", and +.060". Rings can add +.001" to that list. Anything else, and you'll be looking for an "off-list" piece that happens to fit the criteria for what you want.
 
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