Piston Pin Material - Unexpected
Nothing earth shattering here, but this was interesting and also perplexing: As part a little project to modify pin weights, a spread sheet was set up to compute wrist pin weights from volume and material density. EDITED to correct for a spreadsheet error.
The first check of this spreadsheet was for factory 273 2 BBL pins. Measure the pins' dimensions, plug those into the spreadsheet, use a standard density for tool steel of 7.85 gr/cc, and it spits out a weight 0.25% off from what was actually weighed.... well within the scale's accuracy; so far so good. EDIT: Corrected to 7.78 gr/cc.
Next was some small Chevy pins from a modern V6. Put in the numbers and WTF..... the pin material density had to be reduced to 6.6 gr/cc to get the spreadsheet weight to match the actual weight. ...???? EDIT: Corrected to 7.78 gr/cc...... normal!
The last check was for some 340 wrist pins. Now, the materials density has to increase to 8.55 gr/cc to get the spreadsheet to agree with the actual pin weight. EDIT: Corrected to 8.03 gr/cc......
The scale's calibration has been checked in 25 gram increments and that looks right on the money. Can't see/or find any inside tapers in the pins to upset the dimensional computations. So the pin material's densities appear to vary....
For the 340 pins, the materials that match close to the density found are high nickel and/or chromium steel.
Pix of pins, L to R: 273, 340, Chevy V6
Nothing earth shattering here, but this was interesting and also perplexing: As part a little project to modify pin weights, a spread sheet was set up to compute wrist pin weights from volume and material density. EDITED to correct for a spreadsheet error.
The first check of this spreadsheet was for factory 273 2 BBL pins. Measure the pins' dimensions, plug those into the spreadsheet, use a standard density for tool steel of 7.85 gr/cc, and it spits out a weight 0.25% off from what was actually weighed.... well within the scale's accuracy; so far so good. EDIT: Corrected to 7.78 gr/cc.
Next was some small Chevy pins from a modern V6. Put in the numbers and WTF..... the pin material density had to be reduced to 6.6 gr/cc to get the spreadsheet weight to match the actual weight. ...???? EDIT: Corrected to 7.78 gr/cc...... normal!
The last check was for some 340 wrist pins. Now, the materials density has to increase to 8.55 gr/cc to get the spreadsheet to agree with the actual pin weight. EDIT: Corrected to 8.03 gr/cc......
The scale's calibration has been checked in 25 gram increments and that looks right on the money. Can't see/or find any inside tapers in the pins to upset the dimensional computations. So the pin material's densities appear to vary....
For the 340 pins, the materials that match close to the density found are high nickel and/or chromium steel.
Pix of pins, L to R: 273, 340, Chevy V6
