Piston pin offset.

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circlepilot

circlepilot

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The maintenance manual doesn't specify a measurement for piston pin offset. I believe this is automatically achieved when the specified factory tool (C-3724) is used to install the piston pins. Doug Dutra's book says to measure the pin offset during tear down and that measurement will be used used for reassembly. Well...I didn't record the measurement.:( I'm sure that someone here could give me a recommendation.
Norm
 
Ooops!

Just noticed this is the Slant section. It also uses 0.060" offset.
 
The pin ofset is determined by the location of the pin hole, during manufacture. It is used to put a little more side loading on the piston, to quiet noise before the engine reaches normal temp. The only consideration for the engine builder, is to install the piston, with the marking facing to proper way (usually toward the front). Racing pistons do not have pin offset. Back in the old days, in class racing that required using stock pistons, we would install the pistons backwards, to reduce side loading, and supposidly fre up small amount of horsepower.
 
I think the OP is actually needing to know dimensions regarding the reinstallation of the piston pin when assembling the piston/rod. How far to press the pin.
I don't know, I would need to measure an old piston/rod assembly.
 
Charrlie_S said:
The pin ofset is determined by the location of the pin hole, during manufacture. It is used to put a little more side loading on the piston, to quiet noise before the engine reaches normal temp. The only consideration for the engine builder, is to install the piston, with the marking facing to proper way (usually toward the front). Racing pistons do not have pin offset. Back in the old days, in class racing that required using stock pistons, we would install the pistons backwards, to reduce side loading, and supposidly fre up small amount of horsepower.
Click to expand...


So what you are saying Charrlie..."no offset," if raced, right?
Norm
 
Pin installation should not differ. Just get the tally marks facing forward. How far to press the pin in...centered on the rod. No difference
 
pishta said:
Pin installation should not differ. Just get the tally marks facing forward. How far to press the pin in...centered on the rod. No difference
Click to expand...

I think the OP is confused about what the pin offset is. Has nothing to do with how far to press the pin in or whether the pin is centered in the rod; pin offset refers to where the hole for the pin is in the piston - in the middle or toward the major or minor thrust side of the cylinder. That is determined by the piston manufacturer. Factory pistons offset the pin location toward the major thrust side of the cylinder to reduce piston slap when cold, at the expense of a slight increase in friction. I haven't really kept up with the latest developments, but I think that some aftermarket race pistons actually offset the pin location the other way. What is Wrist Pin Offset?

So anyway, how you install the pin, or how deeply you install it into the rod, has nothing to do with pin offset. And yeah, just center the pin in the rod.
 
circlepilot said:
So what you are saying Charrlie..."no offset," if raced, right?
Norm
Click to expand...
Not correct. If using stock replacement pistons The pin will have an offset, it cannot be changed. Only if it is on the major, or minor thrust side, depending whether the piston is installed with the locating mark facing forward or back. It is in the design of the piston. Most "race" pistons do not have a pin offset. The pin is located on the piston centerline.
 
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