piston Q

[POLAR_JEEP_04]

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.

 

[gradon]

+.020",.030"., and .060" are common sizes--dunno if I've seen a +.050".

 

[POLAR_JEEP_04]

i know that but what is that 50 on the top of the piston?

 

[gradon]

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.

 

[Talyn]

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.

 

[gradon]

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).

 

[POLAR_JEEP_04]

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

 

[5-90]

"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.

 

[POLAR_JEEP_04]

cool thanks 5-90